Release v5.3.1

Fix checkstyle violation
Polishing in DefaultWebClient
2026-06-08 17:33:33 +00:00 · 2020-11-10 08:59:43 +00:00 · 2020-11-09 22:30:35 +00:00 · 2020-11-09 22:07:31 +00:00 · 2020-11-09 22:07:31 +00:00 · 2020-11-09 21:33:32 +01:00
304 changed files with 10393 additions and 3102 deletions
@@ -26,21 +26,21 @@ configure(allprojects) { project ->
 	dependencyManagement {
 		imports {
 			mavenBom "com.fasterxml.jackson:jackson-bom:2.11.3"
-			mavenBom "io.netty:netty-bom:4.1.52.Final"
-			mavenBom "io.projectreactor:reactor-bom:2020.0.0-RC2"
-			mavenBom "io.r2dbc:r2dbc-bom:Arabba-SR7"
-			mavenBom "io.rsocket:rsocket-bom:1.1.0-RC1"
-			mavenBom "org.eclipse.jetty:jetty-bom:9.4.32.v20200930"
+			mavenBom "io.netty:netty-bom:4.1.53.Final"
+			mavenBom "io.projectreactor:reactor-bom:2020.0.0"
+			mavenBom "io.r2dbc:r2dbc-bom:Arabba-SR8"
+			mavenBom "io.rsocket:rsocket-bom:1.1.0"
+			mavenBom "org.eclipse.jetty:jetty-bom:9.4.34.v20201102"
 			mavenBom "org.jetbrains.kotlin:kotlin-bom:1.4.10"
-			mavenBom "org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.4.0-M1"
+			mavenBom "org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.4.1"
 			mavenBom "org.junit:junit-bom:5.7.0"
 		}
 		dependencies {
 			dependencySet(group: 'org.apache.logging.log4j', version: '2.13.3') {
 				entry 'log4j-api'
 				entry 'log4j-core'
-				entry 'log4j-slf4j-impl'
 				entry 'log4j-jul'
+				entry 'log4j-slf4j-impl'
 			}
 			dependency "org.slf4j:slf4j-api:1.7.30"
 			dependency("com.google.code.findbugs:findbugs:3.0.1") {
@@ -65,11 +65,11 @@ configure(allprojects) { project ->
 			dependency "io.reactivex:rxjava-reactive-streams:1.2.1"
 			dependency "io.reactivex.rxjava2:rxjava:2.2.19"
 			dependency "io.reactivex.rxjava3:rxjava:3.0.7"
-			dependency "io.projectreactor.tools:blockhound:1.0.2.RELEASE"
+			dependency "io.projectreactor.tools:blockhound:1.0.4.RELEASE"

 			dependency "com.caucho:hessian:4.0.63"
 			dependency "com.fasterxml:aalto-xml:1.2.2"
-			dependency("com.fasterxml.woodstox:woodstox-core:6.2.1") {
+			dependency("com.fasterxml.woodstox:woodstox-core:6.2.3") {
 				exclude group: "stax", name: "stax-api"
 			}
 			dependency "com.google.code.gson:gson:2.8.6"
@@ -88,7 +88,7 @@ configure(allprojects) { project ->
 				entry 'jibx-run'
 			}
 			dependency "org.ogce:xpp3:1.1.6"
-			dependency "org.yaml:snakeyaml:1.26"
+			dependency "org.yaml:snakeyaml:1.27"
 			dependencySet(group: 'org.jetbrains.kotlinx', version: '1.0.0') {
 				entry 'kotlinx-serialization-core'
 				entry 'kotlinx-serialization-json'
@@ -123,19 +123,19 @@ configure(allprojects) { project ->
 			dependency "net.sf.ehcache:ehcache:2.10.6"
 			dependency "org.ehcache:jcache:1.0.1"
 			dependency "org.ehcache:ehcache:3.4.0"
-			dependency "org.hibernate:hibernate-core:5.4.22.Final"
+			dependency "org.hibernate:hibernate-core:5.4.23.Final"
 			dependency "org.hibernate:hibernate-validator:6.1.6.Final"
 			dependency "org.webjars:webjars-locator-core:0.46"
 			dependency "org.webjars:underscorejs:1.8.3"

-			dependencySet(group: 'org.apache.tomcat', version: '9.0.38') {
+			dependencySet(group: 'org.apache.tomcat', version: '9.0.39') {
 				entry 'tomcat-util'
 				entry('tomcat-websocket') {
 					exclude group: "org.apache.tomcat", name: "tomcat-websocket-api"
 					exclude group: "org.apache.tomcat", name: "tomcat-servlet-api"
 				}
 			}
-			dependencySet(group: 'org.apache.tomcat.embed', version: '9.0.38') {
+			dependencySet(group: 'org.apache.tomcat.embed', version: '9.0.39') {
 				entry 'tomcat-embed-core'
 				entry 'tomcat-embed-websocket'
 			}
@@ -161,7 +161,7 @@ configure(allprojects) { project ->
 				exclude group: "commons-logging", name: "commons-logging"
 			}
 			dependency 'org.apache.httpcomponents.client5:httpclient5:5.0.3'
-			dependency 'org.apache.httpcomponents.core5:httpcore5-reactive:5.0.3'
+			dependency 'org.apache.httpcomponents.core5:httpcore5-reactive:5.0.2'
 			dependency "org.eclipse.jetty:jetty-reactive-httpclient:1.1.4"

 			dependency "org.jruby:jruby:9.2.13.0"
@@ -190,14 +190,14 @@ configure(allprojects) { project ->
 			dependency "org.testng:testng:7.3.0"
 			dependency "org.hamcrest:hamcrest:2.1"
 			dependency "org.awaitility:awaitility:3.1.6"
-			dependency "org.assertj:assertj-core:3.17.2"
+			dependency "org.assertj:assertj-core:3.18.0"
 			dependencySet(group: 'org.xmlunit', version: '2.6.2') {
 				entry 'xmlunit-assertj'
 				entry('xmlunit-matchers') {
 					exclude group: "org.hamcrest", name: "hamcrest-core"
 				}
 			}
-			dependencySet(group: 'org.mockito', version: '3.5.13') {
+			dependencySet(group: 'org.mockito', version: '3.6.0') {
 				entry('mockito-core') {
 					exclude group: "org.hamcrest", name: "hamcrest-core"
 				}
@@ -291,7 +291,6 @@ configure(allprojects) { project ->
 		repositories {
 			mavenCentral()
 			maven { url "https://repo.spring.io/libs-spring-framework-build" }
-			maven { url "https://repo.spring.io/milestone" } // Reactor
 		}
 	}
 	configurations.all {
@@ -380,6 +379,7 @@ configure([rootProject] + javaProjects) { project ->
 			"https://fasterxml.github.io/jackson-databind/javadoc/2.10/",
 			"https://fasterxml.github.io/jackson-dataformat-xml/javadoc/2.10/",
 			"https://hc.apache.org/httpcomponents-client-ga/httpclient/apidocs/",
+			"https://projectreactor.io/docs/test/release/api/",
 			"https://junit.org/junit4/javadoc/4.13.1/",
 			"https://junit.org/junit5/docs/5.7.0/api/"
 	] as String[]
@@ -0,0 +1,17 @@
+changelog:
+  repository: spring-projects/spring-framework
+  sections:
+    - title: ":star: New Features"
+      labels:
+        - "type: enhancement"
+    - title: ":beetle: Bug Fixes"
+      labels:
+        - "type: bug"
+        - "type: regression"
+    - title: ":notebook_with_decorative_cover: Documentation"
+      labels:
+        - "type: documentation"
+    - title: ":hammer: Dependency Upgrades"
+      sort: "title"
+      labels:
+        - "type: dependency-upgrade"
@@ -0,0 +1,9 @@
+logging:
+  level:
+    io.spring.concourse: DEBUG
+distribute:
+  optional-deployments:
+    - '.*\\.zip'
+spring:
+  main:
+    banner-mode: off
@@ -11,7 +11,7 @@ rm -rf /var/lib/apt/lists/*

 curl https://raw.githubusercontent.com/spring-io/concourse-java-scripts/v0.0.3/concourse-java.sh > /opt/concourse-java.sh

-curl --output /opt/concourse-release-scripts.jar https://repo.spring.io/release/io/spring/concourse/releasescripts/concourse-release-scripts/0.2.0/concourse-release-scripts-0.2.0.jar
+curl --output /opt/concourse-release-scripts.jar https://repo.spring.io/release/io/spring/concourse/releasescripts/concourse-release-scripts/0.2.1/concourse-release-scripts-0.2.1.jar

 ###########################################################
 # JAVA
@@ -1,28 +1,61 @@
+anchors:
+  artifactory-task-params: &artifactory-task-params
+    ARTIFACTORY_SERVER: ((artifactory-server))
+    ARTIFACTORY_USERNAME: ((artifactory-username))
+    ARTIFACTORY_PASSWORD: ((artifactory-password))
+  bintray-task-params: &bintray-task-params
+    BINTRAY_SUBJECT: ((bintray-subject))
+    BINTRAY_REPO: ((bintray-repo))
+    BINTRAY_USERNAME: ((bintray-username))
+    BINTRAY_API_KEY: ((bintray-api-key))
+  docker-resource-source: &docker-resource-source
+    username: ((docker-hub-username))
+    password: ((docker-hub-password))
+    tag: 5.3.x
+  gradle-enterprise-task-params: &gradle-enterprise-task-params
+    GRADLE_ENTERPRISE_ACCESS_KEY: ((gradle_enterprise_secret_access_key))
+    GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
+    GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
+  slack-fail-params: &slack-fail-params
+    text: >
+      :concourse-failed: <https://ci.spring.io/teams/${BUILD_TEAM_NAME}/pipelines/${BUILD_PIPELINE_NAME}/jobs/${BUILD_JOB_NAME}/builds/${BUILD_NAME}|${BUILD_PIPELINE_NAME} ${BUILD_JOB_NAME} failed!>
+      [$TEXT_FILE_CONTENT]
+    text_file: git-repo/build/build-scan-uri.txt
+    silent: true
+    icon_emoji: ":concourse:"
+    username: concourse-ci
+  sonatype-task-params: &sonatype-task-params
+    SONATYPE_USER_TOKEN: ((sonatype-user-token))
+    SONATYPE_PASSWORD_TOKEN: ((sonatype-user-token-password))
+  changelog-task-params: &changelog-task-params
+    name: generated-changelog/tag
+    tag: generated-changelog/tag
+    body: generated-changelog/changelog.md
+  github-task-params: &github-task-params
+    GITHUB_USERNAME: ((github-username))
+    GITHUB_TOKEN: ((github-ci-release-token))
+
 resource_types:
 - name: artifactory-resource
  type: docker-image
  source:
    repository: springio/artifactory-resource
-    tag: 0.0.12-SNAPSHOT
+    tag: 0.0.12
 - name: github-status-resource
  type: docker-image
  source:
    repository: dpb587/github-status-resource
    tag: master
- name: email
-  type: docker-image
-  source:
-    repository: pcfseceng/email-resource
-    tag: 1.0.19
 - name: slack-notification
  type: docker-image
  source:
    repository: cfcommunity/slack-notification-resource
    tag: latest
+
 resources:
 - name: git-repo
  type: git
-  icon: github-circle
+  icon: github
  source:
    uri: ((github-repo))
    username: ((github-username))
@@ -37,7 +70,7 @@ resources:
    location: Europe/Vienna
 - name: ci-images-git-repo
  type: git
-  icon: github-circle
+  icon: github
  source:
    uri: ((github-repo))
    branch: ((branch))
@@ -46,34 +79,26 @@ resources:
  type: docker-image
  icon: docker
  source:
+    <<: *docker-resource-source
    repository: ((docker-hub-organization))/spring-framework-ci-image
-    username: ((docker-hub-username))
-    password: ((docker-hub-password))
-    tag: 5.3.x
 - name: spring-framework-jdk11-ci-image
  type: docker-image
  icon: docker
  source:
+    <<: *docker-resource-source
    repository: ((docker-hub-organization))/spring-framework-jdk11-ci-image
-    username: ((docker-hub-username))
-    password: ((docker-hub-password))
-    tag: 5.3.x
 - name: spring-framework-jdk14-ci-image
  type: docker-image
  icon: docker
  source:
+    <<: *docker-resource-source
    repository: ((docker-hub-organization))/spring-framework-jdk14-ci-image
-    username: ((docker-hub-username))
-    password: ((docker-hub-password))
-    tag: 5.3.x
 - name: spring-framework-jdk15-ci-image
  type: docker-image
  icon: docker
  source:
+    <<: *docker-resource-source
    repository: ((docker-hub-organization))/spring-framework-jdk15-ci-image
-    username: ((docker-hub-username))
-    password: ((docker-hub-password))
-    tag: 5.3.x
 - name: artifactory-repo
  type: artifactory-resource
  icon: package-variant
@@ -119,6 +144,24 @@ resources:
  icon: slack
  source:
    url: ((slack-webhook-url))
+- name: github-pre-release
+  type: github-release
+  icon: briefcase-download-outline
+  source:
+    owner: spring-projects
+    repository: spring-framework
+    access_token: ((github-ci-release-token))
+    pre_release: true
+    release: false
+- name: github-release
+  type: github-release
+  icon: briefcase-download
+  source:
+    owner: spring-projects
+    repository: spring-framework
+    access_token: ((github-ci-release-token))
+    pre_release: false
+
 jobs:
 - name: build-spring-framework-ci-images
  plan:
@@ -158,23 +201,14 @@ jobs:
      file: git-repo/ci/tasks/build-project.yml
      params:
        BRANCH: ((branch))
-        GRADLE_ENTERPRISE_ACCESS_KEY: ((gradle_enterprise_secret_access_key))
-        GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
-        GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
+        <<: *gradle-enterprise-task-params
    on_failure:
      do:
      - put: repo-status-build
        params: { state: "failure", commit: "git-repo" }
      - put: slack-alert
        params:
-          text: >
-            :concourse-failed: ${BUILD_PIPELINE_NAME} ${BUILD_JOB_NAME} failed!
-            [<https://ci.spring.io/teams/${BUILD_TEAM_NAME}/pipelines/${BUILD_PIPELINE_NAME}/jobs/${BUILD_JOB_NAME}/builds/${BUILD_NAME}|build log>]
-            [<$TEXT_FILE_CONTENT|build scan>]
-          text_file: git-repo/build/build-scan-uri.txt
-          silent: true
-          icon_emoji: ":concourse:"
-          username: concourse-ci
+          <<: *slack-fail-params
  - put: repo-status-build
    params: { state: "success", commit: "git-repo" }
  - put: artifactory-repo
@@ -224,23 +258,14 @@ jobs:
      file: git-repo/ci/tasks/check-project.yml
      params:
        BRANCH: ((branch))
-        GRADLE_ENTERPRISE_ACCESS_KEY: ((gradle_enterprise_secret_access_key))
-        GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
-        GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
+        <<: *gradle-enterprise-task-params
    on_failure:
      do:
      - put: repo-status-jdk11-build
        params: { state: "failure", commit: "git-repo" }
      - put: slack-alert
        params:
-          text: >
-            :concourse-failed: ${BUILD_PIPELINE_NAME} ${BUILD_JOB_NAME} failed!
-            [<https://ci.spring.io/teams/${BUILD_TEAM_NAME}/pipelines/${BUILD_PIPELINE_NAME}/jobs/${BUILD_JOB_NAME}/builds/${BUILD_NAME}|build log>]
-            [<$TEXT_FILE_CONTENT|build scan>]
-          text_file: git-repo/build/build-scan-uri.txt
-          silent: true
-          icon_emoji: ":concourse:"
-          username: concourse-ci
+          <<: *slack-fail-params
  - put: repo-status-jdk11-build
    params: { state: "success", commit: "git-repo" }
 - name: jdk14-build
@@ -261,23 +286,14 @@ jobs:
        file: git-repo/ci/tasks/check-project.yml
        params:
          BRANCH: ((branch))
-          GRADLE_ENTERPRISE_ACCESS_KEY: ((gradle_enterprise_secret_access_key))
-          GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
-          GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
+          <<: *gradle-enterprise-task-params
      on_failure:
        do:
          - put: repo-status-jdk14-build
            params: { state: "failure", commit: "git-repo" }
          - put: slack-alert
            params:
-              text: >
-                :concourse-failed: ${BUILD_PIPELINE_NAME} ${BUILD_JOB_NAME} failed!
-                [<https://ci.spring.io/teams/${BUILD_TEAM_NAME}/pipelines/${BUILD_PIPELINE_NAME}/jobs/${BUILD_JOB_NAME}/builds/${BUILD_NAME}|build log>]
-                [<$TEXT_FILE_CONTENT|build scan>]
-              text_file: git-repo/build/build-scan-uri.txt
-              silent: true
-              icon_emoji: ":concourse:"
-              username: concourse-ci
+              <<: *slack-fail-params
    - put: repo-status-jdk14-build
      params: { state: "success", commit: "git-repo" }
 - name: jdk15-build
@@ -298,23 +314,14 @@ jobs:
          file: git-repo/ci/tasks/check-project.yml
          params:
            BRANCH: ((branch))
-            GRADLE_ENTERPRISE_ACCESS_KEY: ((gradle_enterprise_secret_access_key))
-            GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
-            GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
+            <<: *gradle-enterprise-task-params
      on_failure:
        do:
          - put: repo-status-jdk15-build
            params: { state: "failure", commit: "git-repo" }
          - put: slack-alert
            params:
-              text: >
-                :concourse-failed: ${BUILD_PIPELINE_NAME} ${BUILD_JOB_NAME} failed!
-                [<https://ci.spring.io/teams/${BUILD_TEAM_NAME}/pipelines/${BUILD_PIPELINE_NAME}/jobs/${BUILD_JOB_NAME}/builds/${BUILD_NAME}|build log>]
-                [<$TEXT_FILE_CONTENT|build scan>]
-              text_file: git-repo/build/build-scan-uri.txt
-              silent: true
-              icon_emoji: ":concourse:"
-              username: concourse-ci
+              <<: *slack-fail-params
    - put: repo-status-jdk15-build
      params: { state: "success", commit: "git-repo" }
 - name: stage-milestone
@@ -328,9 +335,7 @@ jobs:
      file: git-repo/ci/tasks/stage-version.yml
      params:
        RELEASE_TYPE: M
-        GRADLE_ENTERPRISE_ACCESS_KEY: ((gradle_enterprise_secret_access_key))
-        GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
-        GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
+        <<: *gradle-enterprise-task-params
    - put: artifactory-repo
      params:
        <<: *artifactory-params
@@ -355,9 +360,15 @@ jobs:
      file: git-repo/ci/tasks/promote-version.yml
      params:
        RELEASE_TYPE: M
-        ARTIFACTORY_SERVER: ((artifactory-server))
-        ARTIFACTORY_USERNAME: ((artifactory-username))
-        ARTIFACTORY_PASSWORD: ((artifactory-password))
+        <<: *artifactory-task-params
+    - task: generate-changelog
+      file: git-repo/ci/tasks/generate-changelog.yml
+      params:
+        RELEASE_TYPE: M
+        <<: *github-task-params
+    - put: github-pre-release
+      params:
+        <<: *changelog-task-params
 - name: stage-rc
  serial: true
  plan:
@@ -369,9 +380,7 @@ jobs:
      file: git-repo/ci/tasks/stage-version.yml
      params:
        RELEASE_TYPE: RC
-        GRADLE_ENTERPRISE_ACCESS_KEY: ((gradle_enterprise_secret_access_key))
-        GRADLE_ENTERPRISE_CACHE_USERNAME: ((gradle_enterprise_cache_user.username))
-        GRADLE_ENTERPRISE_CACHE_PASSWORD: ((gradle_enterprise_cache_user.password))
+        <<: *gradle-enterprise-task-params
    - put: artifactory-repo
      params:
        <<: *artifactory-params
@@ -396,13 +405,83 @@ jobs:
      file: git-repo/ci/tasks/promote-version.yml
      params:
        RELEASE_TYPE: RC
-        ARTIFACTORY_SERVER: ((artifactory-server))
-        ARTIFACTORY_USERNAME: ((artifactory-username))
-        ARTIFACTORY_PASSWORD: ((artifactory-password))
+        <<: *artifactory-task-params
+    - task: generate-changelog
+      file: git-repo/ci/tasks/generate-changelog.yml
+      params:
+        RELEASE_TYPE: RC
+        <<: *github-task-params
+    - put: github-pre-release
+      params:
+        <<: *changelog-task-params
+- name: stage-release
+  serial: true
+  plan:
+    - get: spring-framework-ci-image
+    - get: git-repo
+      trigger: false
+    - task: stage
+      image: spring-framework-ci-image
+      file: git-repo/ci/tasks/stage-version.yml
+      params:
+        RELEASE_TYPE: RELEASE
+        <<: *gradle-enterprise-task-params
+    - put: artifactory-repo
+      params:
+        <<: *artifactory-params
+        repo: libs-staging-local
+    - put: git-repo
+      params:
+        repository: stage-git-repo
+- name: promote-release
+  serial: true
+  plan:
+    - get: spring-framework-ci-image
+    - get: git-repo
+      trigger: false
+    - get: artifactory-repo
+      trigger: false
+      passed: [stage-release]
+      params:
+        download_artifacts: false
+        save_build_info: true
+    - task: promote
+      image: spring-framework-ci-image
+      file: git-repo/ci/tasks/promote-version.yml
+      params:
+        RELEASE_TYPE: RELEASE
+        <<: *artifactory-task-params
+        <<: *bintray-task-params
+- name: sync-to-maven-central
+  serial: true
+  plan:
+    - get: spring-framework-ci-image
+    - get: git-repo
+    - get: artifactory-repo
+      trigger: true
+      passed: [promote-release]
+      params:
+        download_artifacts: false
+        save_build_info: true
+    - task: sync-to-maven-central
+      image: spring-framework-ci-image
+      file: git-repo/ci/tasks/sync-to-maven-central.yml
+      params:
+        <<: *bintray-task-params
+        <<: *sonatype-task-params
+    - task: generate-changelog
+      file: git-repo/ci/tasks/generate-changelog.yml
+      params:
+        RELEASE_TYPE: RELEASE
+        <<: *github-task-params
+    - put: github-release
+      params:
+        <<: *changelog-task-params
+
 groups:
- name: "Build"
+- name: "builds"
  jobs: ["build", "jdk11-build", "jdk14-build", "jdk15-build"]
- name: "Release"
-  jobs: ["stage-milestone","stage-rc", "promote-milestone","promote-rc"]
- name: "CI Images"
+- name: "releases"
+  jobs: ["stage-milestone", "stage-rc", "stage-release", "promote-milestone","promote-rc", "promote-release", "sync-to-maven-central"]
+- name: "ci-images"
  jobs: ["build-spring-framework-ci-images"]
@@ -0,0 +1,12 @@
+#!/bin/bash
+set -e
+
+CONFIG_DIR=git-repo/ci/config
+version=$( cat version/version )
+
+java -jar /github-changelog-generator.jar \
+  --spring.config.location=${CONFIG_DIR}/changelog-generator.yml \
+  ${version} generated-changelog/changelog.md
+
+echo ${version} > generated-changelog/version
+echo v${version} > generated-changelog/tag
@@ -1,13 +1,16 @@
 #!/bin/bash

 source $(dirname $0)/common.sh
+CONFIG_DIR=git-repo/ci/config

 version=$( cat artifactory-repo/build-info.json | jq -r '.buildInfo.modules[0].id' | sed 's/.*:.*:\(.*\)/\1/' )
 export BUILD_INFO_LOCATION=$(pwd)/artifactory-repo/build-info.json

 java -jar /opt/concourse-release-scripts.jar promote $RELEASE_TYPE $BUILD_INFO_LOCATION > /dev/null || { exit 1; }

-java -jar /opt/concourse-release-scripts.jar distribute $RELEASE_TYPE $BUILD_INFO_LOCATION > /dev/null || { exit 1; }
+java -jar /opt/concourse-release-scripts.jar \
+  --spring.config.location=${CONFIG_DIR}/release-scripts.yml \
+  distribute $RELEASE_TYPE $BUILD_INFO_LOCATION > /dev/null || { exit 1; }

 echo "Promotion complete"
 echo $version > version/version
@@ -0,0 +1,8 @@
+#!/bin/bash
+
+export BUILD_INFO_LOCATION=$(pwd)/artifactory-repo/build-info.json
+version=$( cat artifactory-repo/build-info.json | jq -r '.buildInfo.modules[0].id' | sed 's/.*:.*:\(.*\)/\1/' )
+java -jar /opt/concourse-release-scripts.jar syncToCentral "RELEASE" $BUILD_INFO_LOCATION || { exit 1; }
+
+echo "Sync complete"
+echo $version > version/version
@@ -0,0 +1,20 @@
+---
+platform: linux
+image_resource:
+  type: docker-image
+  source:
+    repository: springio/github-changelog-generator
+    tag: '0.0.4'
+inputs:
+- name: git-repo
+- name: version
+outputs:
+- name: generated-changelog
+params:
+  GITHUB_ORGANIZATION:
+  GITHUB_REPO:
+  GITHUB_USERNAME:
+  GITHUB_TOKEN:
+  RELEASE_TYPE:
+run:
+  path: git-repo/ci/scripts/generate-changelog.sh
@@ -0,0 +1,16 @@
+---
+platform: linux
+inputs:
+- name: git-repo
+- name: artifactory-repo
+outputs:
+- name: version
+params:
+  BINTRAY_REPO:
+  BINTRAY_SUBJECT:
+  BINTRAY_USERNAME:
+  BINTRAY_API_KEY:
+  SONATYPE_USER_TOKEN:
+  SONATYPE_PASSWORD_TOKEN:
+run:
+  path: git-repo/ci/scripts/sync-to-maven-central.sh
@@ -1,4 +1,4 @@
-version=5.3.0-RC2
+version=5.3.1
 org.gradle.jvmargs=-Xmx1536M
 org.gradle.caching=true
 org.gradle.parallel=true
@@ -106,6 +106,9 @@ dokka {
 		externalDocumentationLink {
 			url = new URL("https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/")
 		}
+		externalDocumentationLink {
+			url = new URL("https://r2dbc.io/spec/0.8.3.RELEASE/api/")
+		}
 	}
 }

@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.6.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
@@ -221,10 +221,12 @@ public class MethodInvocationProceedingJoinPoint implements ProceedingJoinPoint,
 		@Override
 		@Nullable
 		public String[] getParameterNames() {
-			if (this.parameterNames == null) {
-				this.parameterNames = parameterNameDiscoverer.getParameterNames(getMethod());
+			String[] parameterNames = this.parameterNames;
+			if (parameterNames == null) {
+				parameterNames = parameterNameDiscoverer.getParameterNames(getMethod());
+				this.parameterNames = parameterNames;
 			}
-			return this.parameterNames;
+			return parameterNames;
 		}

 		@Override
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -160,23 +160,12 @@ public class AspectJProxyFactory extends ProxyCreatorSupport {
 	}

 	/**
-	 * Get the singleton aspect instance for the supplied aspect type. An instance
-	 * is created if one cannot be found in the instance cache.
+	 * Get the singleton aspect instance for the supplied aspect type.
+	 * An instance is created if one cannot be found in the instance cache.
 	 */
 	private Object getSingletonAspectInstance(Class<?> aspectClass) {
-		// Quick check without a lock...
-		Object instance = aspectCache.get(aspectClass);
-		if (instance == null) {
-			synchronized (aspectCache) {
-				// To be safe, check within full lock now...
-				instance = aspectCache.get(aspectClass);
-				if (instance == null) {
-					instance = new SimpleAspectInstanceFactory(aspectClass).getAspectInstance();
-					aspectCache.put(aspectClass, instance);
-				}
-			}
-		}
-		return instance;
+		return aspectCache.computeIfAbsent(aspectClass,
+				clazz -> new SimpleAspectInstanceFactory(clazz).getAspectInstance());
 	}


@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -114,6 +114,15 @@ public interface Advised extends TargetClassAware {
 	 */
 	Advisor[] getAdvisors();

+	/**
+	 * Return the number of advisors applying to this proxy.
+	 * <p>The default implementation delegates to {@code getAdvisors().length}.
+	 * @since 5.3.1
+	 */
+	default int getAdvisorCount() {
+		return getAdvisors().length;
+	}
+
 	/**
 	 * Add an advisor at the end of the advisor chain.
 	 * <p>The Advisor may be an {@link org.springframework.aop.IntroductionAdvisor},
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -95,12 +95,6 @@ public class AdvisedSupport extends ProxyConfig implements Advised {
 	 */
 	private List<Advisor> advisors = new ArrayList<>();

-	/**
-	 * Array updated on changes to the advisors list, which is easier
-	 * to manipulate internally.
-	 */
-	private Advisor[] advisorArray = new Advisor[0];
-

 	/**
 	 * No-arg constructor for use as a JavaBean.
@@ -244,7 +238,12 @@ public class AdvisedSupport extends ProxyConfig implements Advised {

 	@Override
 	public final Advisor[] getAdvisors() {
-		return this.advisorArray;
+		return this.advisors.toArray(new Advisor[0]);
+	}
+
+	@Override
+	public int getAdvisorCount() {
+		return this.advisors.size();
 	}

 	@Override
@@ -292,7 +291,6 @@ public class AdvisedSupport extends ProxyConfig implements Advised {
 			}
 		}

-		updateAdvisorArray();
 		adviceChanged();
 	}

@@ -339,7 +337,6 @@ public class AdvisedSupport extends ProxyConfig implements Advised {
 				Assert.notNull(advisor, "Advisor must not be null");
 				this.advisors.add(advisor);
 			}
-			updateAdvisorArray();
 			adviceChanged();
 		}
 	}
@@ -363,27 +360,18 @@ public class AdvisedSupport extends ProxyConfig implements Advised {
 					"Illegal position " + pos + " in advisor list with size " + this.advisors.size());
 		}
 		this.advisors.add(pos, advisor);
-		updateAdvisorArray();
 		adviceChanged();
 	}

-	/**
-	 * Bring the array up to date with the list.
-	 */
-	protected final void updateAdvisorArray() {
-		this.advisorArray = this.advisors.toArray(new Advisor[0]);
-	}
-
 	/**
 	 * Allows uncontrolled access to the {@link List} of {@link Advisor Advisors}.
-	 * <p>Use with care, and remember to {@link #updateAdvisorArray() refresh the advisor array}
-	 * and {@link #adviceChanged() fire advice changed events} when making any modifications.
+	 * <p>Use with care, and remember to {@link #adviceChanged() fire advice changed events}
+	 * when making any modifications.
 	 */
 	protected final List<Advisor> getAdvisorsInternal() {
 		return this.advisors;
 	}

-
 	@Override
 	public void addAdvice(Advice advice) throws AopConfigException {
 		int pos = this.advisors.size();
@@ -521,7 +509,6 @@ public class AdvisedSupport extends ProxyConfig implements Advised {
 			Assert.notNull(advisor, "Advisor must not be null");
 			this.advisors.add(advisor);
 		}
-		updateAdvisorArray();
 		adviceChanged();
 	}

@@ -536,7 +523,6 @@ public class AdvisedSupport extends ProxyConfig implements Advised {
 		copy.advisorChainFactory = this.advisorChainFactory;
 		copy.interfaces = this.interfaces;
 		copy.advisors = this.advisors;
-		copy.updateAdvisorArray();
 		return copy;
 	}

@@ -553,7 +539,6 @@ public class AdvisedSupport extends ProxyConfig implements Advised {
 		this.methodCache = new ConcurrentHashMap<>(32);
 	}

-
 	@Override
 	public String toProxyConfigString() {
 		return toString();
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -206,7 +206,7 @@ public abstract class AopProxyUtils {
 	 * Check equality of the advisors behind the given AdvisedSupport objects.
 	 */
 	public static boolean equalsAdvisors(AdvisedSupport a, AdvisedSupport b) {
-		return Arrays.equals(a.getAdvisors(), b.getAdvisors());
+		return a.getAdvisorCount() == b.getAdvisorCount() && Arrays.equals(a.getAdvisors(), b.getAdvisors());
 	}


@@ -125,7 +125,7 @@ class CglibAopProxy implements AopProxy, Serializable {
 	 */
 	public CglibAopProxy(AdvisedSupport config) throws AopConfigException {
 		Assert.notNull(config, "AdvisedSupport must not be null");
-		if (config.getAdvisors().length == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) {
+		if (config.getAdvisorCount() == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) {
 			throw new AopConfigException("No advisors and no TargetSource specified");
 		}
 		this.advised = config;
@@ -942,11 +942,11 @@ class CglibAopProxy implements AopProxy, Serializable {
 			}
 			// Advice instance identity is unimportant to the proxy class:
 			// All that matters is type and ordering.
-			Advisor[] thisAdvisors = this.advised.getAdvisors();
-			Advisor[] thatAdvisors = otherAdvised.getAdvisors();
-			if (thisAdvisors.length != thatAdvisors.length) {
+			if (this.advised.getAdvisorCount() != otherAdvised.getAdvisorCount()) {
 				return false;
 			}
+			Advisor[] thisAdvisors = this.advised.getAdvisors();
+			Advisor[] thatAdvisors = otherAdvised.getAdvisors();
 			for (int i = 0; i < thisAdvisors.length; i++) {
 				Advisor thisAdvisor = thisAdvisors[i];
 				Advisor thatAdvisor = thatAdvisors[i];
@@ -104,7 +104,7 @@ final class JdkDynamicAopProxy implements AopProxy, InvocationHandler, Serializa
 	 */
 	public JdkDynamicAopProxy(AdvisedSupport config) throws AopConfigException {
 		Assert.notNull(config, "AdvisedSupport must not be null");
-		if (config.getAdvisors().length == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) {
+		if (config.getAdvisorCount() == 0 && config.getTargetSource() == AdvisedSupport.EMPTY_TARGET_SOURCE) {
 			throw new AopConfigException("No advisors and no TargetSource specified");
 		}
 		this.advised = config;
@@ -25,6 +25,7 @@ sourceSets {
 compileGroovy {
 	sourceCompatibility = 1.8
 	targetCompatibility = 1.8
+	options.compilerArgs += "-Werror"
 }

 // This module also builds Kotlin code and the compileKotlin task naturally depends on
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -422,9 +422,12 @@ public abstract class AbstractNestablePropertyAccessor extends AbstractPropertyA
 				}
 				return;
 			}
-			else {
-				throw createNotWritablePropertyException(tokens.canonicalName);
+			if (this.suppressNotWritablePropertyException) {
+				// Optimization for common ignoreUnknown=true scenario since the
+				// exception would be caught and swallowed higher up anyway...
+				return;
 			}
+			throw createNotWritablePropertyException(tokens.canonicalName);
 		}

 		Object oldValue = null;
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -40,6 +40,8 @@ public abstract class AbstractPropertyAccessor extends TypeConverterSupport impl

 	private boolean autoGrowNestedPaths = false;

+	boolean suppressNotWritablePropertyException = false;
+

 	@Override
 	public void setExtractOldValueForEditor(boolean extractOldValueForEditor) {
@@ -89,30 +91,41 @@ public abstract class AbstractPropertyAccessor extends TypeConverterSupport impl
 		List<PropertyAccessException> propertyAccessExceptions = null;
 		List<PropertyValue> propertyValues = (pvs instanceof MutablePropertyValues ?
 				((MutablePropertyValues) pvs).getPropertyValueList() : Arrays.asList(pvs.getPropertyValues()));
-		for (PropertyValue pv : propertyValues) {
-			try {
-				// This method may throw any BeansException, which won't be caught
+
+		if (ignoreUnknown) {
+			this.suppressNotWritablePropertyException = true;
+		}
+		try {
+			for (PropertyValue pv : propertyValues) {
+				// setPropertyValue may throw any BeansException, which won't be caught
 				// here, if there is a critical failure such as no matching field.
 				// We can attempt to deal only with less serious exceptions.
-				setPropertyValue(pv);
-			}
-			catch (NotWritablePropertyException ex) {
-				if (!ignoreUnknown) {
-					throw ex;
+				try {
+					setPropertyValue(pv);
 				}
-				// Otherwise, just ignore it and continue...
-			}
-			catch (NullValueInNestedPathException ex) {
-				if (!ignoreInvalid) {
-					throw ex;
+				catch (NotWritablePropertyException ex) {
+					if (!ignoreUnknown) {
+						throw ex;
+					}
+					// Otherwise, just ignore it and continue...
 				}
-				// Otherwise, just ignore it and continue...
-			}
-			catch (PropertyAccessException ex) {
-				if (propertyAccessExceptions == null) {
-					propertyAccessExceptions = new ArrayList<>();
+				catch (NullValueInNestedPathException ex) {
+					if (!ignoreInvalid) {
+						throw ex;
+					}
+					// Otherwise, just ignore it and continue...
 				}
-				propertyAccessExceptions.add(ex);
+				catch (PropertyAccessException ex) {
+					if (propertyAccessExceptions == null) {
+						propertyAccessExceptions = new ArrayList<>();
+					}
+					propertyAccessExceptions.add(ex);
+				}
+			}
+		}
+		finally {
+			if (ignoreUnknown) {
+				this.suppressNotWritablePropertyException = false;
 			}
 		}

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -92,8 +92,7 @@ public class DirectFieldAccessor extends AbstractNestablePropertyAccessor {
 	@Override
 	protected NotWritablePropertyException createNotWritablePropertyException(String propertyName) {
 		PropertyMatches matches = PropertyMatches.forField(propertyName, getRootClass());
-		throw new NotWritablePropertyException(
-				getRootClass(), getNestedPath() + propertyName,
+		throw new NotWritablePropertyException(getRootClass(), getNestedPath() + propertyName,
 				matches.buildErrorMessage(), matches.getPossibleMatches());
 	}

@@ -644,21 +644,20 @@ public class AutowiredAnnotationBeanPostProcessor implements SmartInstantiationA
 				}
 				synchronized (this) {
 					if (!this.cached) {
+						Object cachedFieldValue = null;
 						if (value != null || this.required) {
-							this.cachedFieldValue = desc;
+							cachedFieldValue = desc;
 							registerDependentBeans(beanName, autowiredBeanNames);
 							if (autowiredBeanNames.size() == 1) {
 								String autowiredBeanName = autowiredBeanNames.iterator().next();
 								if (beanFactory.containsBean(autowiredBeanName) &&
 										beanFactory.isTypeMatch(autowiredBeanName, field.getType())) {
-									this.cachedFieldValue = new ShortcutDependencyDescriptor(
+									cachedFieldValue = new ShortcutDependencyDescriptor(
 											desc, autowiredBeanName, field.getType());
 								}
 							}
 						}
-						else {
-							this.cachedFieldValue = null;
-						}
+						this.cachedFieldValue = cachedFieldValue;
 						this.cached = true;
 					}
 				}
@@ -26,9 +26,6 @@ import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.Set;

-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
-
 import org.springframework.beans.MutablePropertyValues;
 import org.springframework.beans.PropertyValues;
 import org.springframework.beans.factory.support.RootBeanDefinition;
@@ -69,8 +66,6 @@ public class InjectionMetadata {
 	};


-	private static final Log logger = LogFactory.getLog(InjectionMetadata.class);
-
 	private final Class<?> targetClass;

 	private final Collection<InjectedElement> injectedElements;
@@ -110,9 +105,6 @@ public class InjectionMetadata {
 			if (!beanDefinition.isExternallyManagedConfigMember(member)) {
 				beanDefinition.registerExternallyManagedConfigMember(member);
 				checkedElements.add(element);
-				if (logger.isTraceEnabled()) {
-					logger.trace("Registered injected element on class [" + this.targetClass.getName() + "]: " + element);
-				}
 			}
 		}
 		this.checkedElements = checkedElements;
@@ -124,9 +116,6 @@ public class InjectionMetadata {
 				(checkedElements != null ? checkedElements : this.injectedElements);
 		if (!elementsToIterate.isEmpty()) {
 			for (InjectedElement element : elementsToIterate) {
-				if (logger.isTraceEnabled()) {
-					logger.trace("Processing injected element of bean '" + beanName + "': " + element);
-				}
 				element.inject(target, beanName, pvs);
 			}
 		}
@@ -157,7 +146,8 @@ public class InjectionMetadata {
 	 * @since 5.2
 	 */
 	public static InjectionMetadata forElements(Collection<InjectedElement> elements, Class<?> clazz) {
-		return (elements.isEmpty() ? InjectionMetadata.EMPTY : new InjectionMetadata(clazz, elements));
+		return (elements.isEmpty() ? new InjectionMetadata(clazz, Collections.emptyList()) :
+				new InjectionMetadata(clazz, elements));
 	}

 	/**
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -40,7 +40,6 @@ import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.ObjectUtils;
-import org.springframework.util.StringUtils;

 /**
 * {@link AutowireCandidateResolver} implementation that matches bean definition qualifiers
@@ -188,7 +187,7 @@ public class QualifierAnnotationAutowireCandidateResolver extends GenericTypeAwa
 						foundMeta = true;
 						// Only accept fallback match if @Qualifier annotation has a value...
 						// Otherwise it is just a marker for a custom qualifier annotation.
-						if ((fallbackToMeta && StringUtils.isEmpty(AnnotationUtils.getValue(metaAnn))) ||
+						if ((fallbackToMeta && ObjectUtils.isEmpty(AnnotationUtils.getValue(metaAnn))) ||
 								!checkQualifier(bdHolder, metaAnn, typeConverter)) {
 							return false;
 						}
@@ -1288,10 +1288,8 @@ public abstract class AbstractBeanFactory extends FactoryBeanRegistrySupport imp
 	 * @param registry the PropertyEditorRegistry to initialize
 	 */
 	protected void registerCustomEditors(PropertyEditorRegistry registry) {
-		PropertyEditorRegistrySupport registrySupport =
-				(registry instanceof PropertyEditorRegistrySupport ? (PropertyEditorRegistrySupport) registry : null);
-		if (registrySupport != null) {
-			registrySupport.useConfigValueEditors();
+		if (registry instanceof PropertyEditorRegistrySupport) {
+			((PropertyEditorRegistrySupport) registry).useConfigValueEditors();
 		}
 		if (!this.propertyEditorRegistrars.isEmpty()) {
 			for (PropertyEditorRegistrar registrar : this.propertyEditorRegistrars) {
@@ -43,8 +43,6 @@ import java.util.stream.IntStream;
 import javax.annotation.Priority;
 import javax.security.auth.Subject;

-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import org.junit.jupiter.api.Test;

 import org.springframework.beans.BeansException;
@@ -121,8 +119,6 @@ import static org.mockito.Mockito.verify;
 */
 class DefaultListableBeanFactoryTests {

-	private static final Log factoryLog = LogFactory.getLog(DefaultListableBeanFactory.class);
-
 	private DefaultListableBeanFactory lbf = new DefaultListableBeanFactory();


@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -126,7 +126,7 @@ public class DefinitionMetadataEqualsHashCodeTests {
 		assertThat(equal.hashCode()).as("Hash code for equal instances should match").isEqualTo(master.hashCode());

 		assertThat(notEqual).as("Should not be equal").isNotEqualTo(master);
-		assertThat(notEqual.hashCode()).as("Hash code for non-equal instances should not match").isNotEqualTo((long) master.hashCode());
+		assertThat(notEqual.hashCode()).as("Hash code for non-equal instances should not match").isNotEqualTo(master.hashCode());

 		assertThat(subclass).as("Subclass should be equal").isEqualTo(master);
 		assertThat(subclass.hashCode()).as("Hash code for subclass should match").isEqualTo(master.hashCode());
@@ -155,8 +155,7 @@ public abstract class AbstractCacheManager implements CacheManager, Initializing
 	 * @param name the name of the cache to be added
 	 */
 	private void updateCacheNames(String name) {
-		Set<String> cacheNames = new LinkedHashSet<>(this.cacheNames.size() + 1);
-		cacheNames.addAll(this.cacheNames);
+		Set<String> cacheNames = new LinkedHashSet<>(this.cacheNames);
 		cacheNames.add(name);
 		this.cacheNames = Collections.unmodifiableSet(cacheNames);
 	}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
 package org.springframework.context;

 import java.util.EventListener;
+import java.util.function.Consumer;

 /**
 * Interface to be implemented by application event listeners.
@@ -45,4 +46,17 @@ public interface ApplicationListener<E extends ApplicationEvent> extends EventLi
 	 */
 	void onApplicationEvent(E event);

+
+	/**
+	 * Create a new {@code ApplicationListener} for the given payload consumer.
+	 * @param consumer the event payload consumer
+	 * @param <T> the type of the event payload
+	 * @return a corresponding {@code ApplicationListener} instance
+	 * @since 5.3
+	 * @see PayloadApplicationEvent
+	 */
+	static <T> ApplicationListener<PayloadApplicationEvent<T>> forPayload(Consumer<T> consumer) {
+		return event -> consumer.accept(event.getPayload());
+	}
+
 }
@@ -99,7 +99,7 @@ public class ConfigurationClassPostProcessor implements BeanDefinitionRegistryPo
 	 * @see #setBeanNameGenerator
 	 */
 	public static final AnnotationBeanNameGenerator IMPORT_BEAN_NAME_GENERATOR =
-			new FullyQualifiedAnnotationBeanNameGenerator();
+			FullyQualifiedAnnotationBeanNameGenerator.INSTANCE;

 	private static final String IMPORT_REGISTRY_BEAN_NAME =
 			ConfigurationClassPostProcessor.class.getName() + ".importRegistry";
@@ -43,6 +43,15 @@ import org.springframework.util.Assert;
 */
 public class FullyQualifiedAnnotationBeanNameGenerator extends AnnotationBeanNameGenerator {

+	/**
+	 * A convenient constant for a default {@code FullyQualifiedAnnotationBeanNameGenerator}
+	 * instance, as used for configuration-level import purposes.
+	 * @since 5.2.11
+	 */
+	public static final FullyQualifiedAnnotationBeanNameGenerator INSTANCE =
+			new FullyQualifiedAnnotationBeanNameGenerator();
+
+
 	@Override
 	protected String buildDefaultBeanName(BeanDefinition definition) {
 		String beanClassName = definition.getBeanClassName();
@@ -37,6 +37,7 @@ import org.springframework.context.ApplicationEvent;
 import org.springframework.context.PayloadApplicationEvent;
 import org.springframework.context.expression.AnnotatedElementKey;
 import org.springframework.core.BridgeMethodResolver;
+import org.springframework.core.Ordered;
 import org.springframework.core.ReactiveAdapter;
 import org.springframework.core.ReactiveAdapterRegistry;
 import org.springframework.core.ResolvableType;
@@ -95,6 +96,12 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 	private EventExpressionEvaluator evaluator;


+	/**
+	 * Construct a new ApplicationListenerMethodAdapter.
+	 * @param beanName the name of the bean to invoke the listener method on
+	 * @param targetClass the target class that the method is declared on
+	 * @param method the listener method to invoke
+	 */
 	public ApplicationListenerMethodAdapter(String beanName, Class<?> targetClass, Method method) {
 		this.beanName = beanName;
 		this.method = BridgeMethodResolver.findBridgedMethod(method);
@@ -135,7 +142,7 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe

 	private static int resolveOrder(Method method) {
 		Order ann = AnnotatedElementUtils.findMergedAnnotation(method, Order.class);
-		return (ann != null ? ann.value() : 0);
+		return (ann != null ? ann.value() : Ordered.LOWEST_PRECEDENCE);
 	}


@@ -332,6 +339,14 @@ public class ApplicationListenerMethodAdapter implements GenericApplicationListe
 		return this.applicationContext.getBean(this.beanName);
 	}

+	/**
+	 * Return the target listener method.
+	 * @since 5.3
+	 */
+	protected Method getTargetMethod() {
+		return this.targetMethod;
+	}
+
 	/**
 	 * Return the condition to use.
 	 * <p>Matches the {@code condition} attribute of the {@link EventListener}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -29,6 +29,7 @@ import org.springframework.core.Ordered;
 *
 * @author Stephane Nicoll
 * @since 4.2
+ * @see ApplicationListenerMethodAdapter
 */
 public class DefaultEventListenerFactory implements EventListenerFactory, Ordered {

@@ -307,6 +307,23 @@ public class ConfigurationClassProcessingTests {
 		assertThat(tb.getLawyer()).isEqualTo(ctx.getBean(NestedTestBean.class));
 	}

+	@Test  // gh-26019
+	public void autowiringWithDynamicPrototypeBeanClass() {
+		AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(
+				ConfigWithDynamicPrototype.class, PrototypeDependency.class);
+
+		PrototypeInterface p1 = ctx.getBean(PrototypeInterface.class, 1);
+		assertThat(p1).isInstanceOf(PrototypeOne.class);
+		assertThat(((PrototypeOne) p1).prototypeDependency).isNotNull();
+
+		PrototypeInterface p2 = ctx.getBean(PrototypeInterface.class, 2);
+		assertThat(p2).isInstanceOf(PrototypeTwo.class);
+
+		PrototypeInterface p3 = ctx.getBean(PrototypeInterface.class, 1);
+		assertThat(p3).isInstanceOf(PrototypeOne.class);
+		assertThat(((PrototypeOne) p3).prototypeDependency).isNotNull();
+	}
+

 	/**
 	 * Creates a new {@link BeanFactory}, populates it with a {@link BeanDefinition}
@@ -632,4 +649,42 @@ public class ConfigurationClassProcessingTests {
 		}
 	}

+
+	static class PrototypeDependency {
+	}
+
+	interface PrototypeInterface {
+	}
+
+	static class PrototypeOne extends AbstractPrototype {
+
+		@Autowired
+		PrototypeDependency prototypeDependency;
+
+	}
+
+	static class PrototypeTwo extends AbstractPrototype {
+
+		// no autowired dependency here, in contrast to above
+	}
+
+	static class AbstractPrototype implements PrototypeInterface {
+	}
+
+	@Configuration
+	static class ConfigWithDynamicPrototype {
+
+		@Bean
+		@Scope(value = "prototype")
+		public PrototypeInterface getDemoBean( int i) {
+			switch ( i) {
+				case 1: return new PrototypeOne();
+				case 2:
+				default:
+					return new PrototypeTwo();
+
+			}
+		}
+	}
+
 }
@@ -26,6 +26,7 @@ import org.springframework.aop.framework.ProxyFactory;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.ApplicationEvent;
 import org.springframework.context.PayloadApplicationEvent;
+import org.springframework.core.Ordered;
 import org.springframework.core.ResolvableType;
 import org.springframework.core.ResolvableTypeProvider;
 import org.springframework.core.annotation.Order;
@@ -161,7 +162,7 @@ public class ApplicationListenerMethodAdapterTests extends AbstractApplicationEv
 		Method method = ReflectionUtils.findMethod(
 				SampleEvents.class, "handleGenericString", GenericTestEvent.class);
 		ApplicationListenerMethodAdapter adapter = createTestInstance(method);
-		assertThat(adapter.getOrder()).isEqualTo(0);
+		assertThat(adapter.getOrder()).isEqualTo(Ordered.LOWEST_PRECEDENCE);
 	}

 	@Test
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -22,8 +22,11 @@ import java.util.List;
 import org.junit.jupiter.api.Test;

 import org.springframework.context.ApplicationContext;
+import org.springframework.context.ApplicationListener;
+import org.springframework.context.ConfigurableApplicationContext;
 import org.springframework.context.PayloadApplicationEvent;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
+import org.springframework.context.support.GenericApplicationContext;
 import org.springframework.stereotype.Component;

 import static org.assertj.core.api.Assertions.assertThat;
@@ -34,14 +37,42 @@ import static org.assertj.core.api.Assertions.assertThat;
 public class PayloadApplicationEventTests {

 	@Test
-	@SuppressWarnings({ "rawtypes", "resource" })
 	public void testEventClassWithInterface() {
 		ApplicationContext ac = new AnnotationConfigApplicationContext(AuditableListener.class);
-		AuditablePayloadEvent event = new AuditablePayloadEvent<>(this, "xyz");
+
+		AuditablePayloadEvent<String> event = new AuditablePayloadEvent<>(this, "xyz");
 		ac.publishEvent(event);
 		assertThat(ac.getBean(AuditableListener.class).events.contains(event)).isTrue();
 	}

+	@Test
+	public void testProgrammaticEventListener() {
+		List<Auditable> events = new ArrayList<>();
+		ApplicationListener<AuditablePayloadEvent<String>> listener = events::add;
+
+		ConfigurableApplicationContext ac = new GenericApplicationContext();
+		ac.addApplicationListener(listener);
+		ac.refresh();
+
+		AuditablePayloadEvent<String> event = new AuditablePayloadEvent<>(this, "xyz");
+		ac.publishEvent(event);
+		assertThat(events.contains(event)).isTrue();
+	}
+
+	@Test
+	public void testProgrammaticPayloadListener() {
+		List<String> events = new ArrayList<>();
+		ApplicationListener<PayloadApplicationEvent<String>> listener = ApplicationListener.forPayload(events::add);
+
+		ConfigurableApplicationContext ac = new GenericApplicationContext();
+		ac.addApplicationListener(listener);
+		ac.refresh();
+
+		AuditablePayloadEvent<String> event = new AuditablePayloadEvent<>(this, "xyz");
+		ac.publishEvent(event);
+		assertThat(events.contains(event.getPayload())).isTrue();
+	}
+

 	public interface Auditable {
 	}
@@ -55,20 +55,20 @@ dependencies {
 	optional("io.reactivex.rxjava3:rxjava")
 	optional("io.netty:netty-buffer")
 	testCompile("io.projectreactor:reactor-test")
-	testCompile("javax.annotation:javax.annotation-api")
 	testCompile("com.google.code.findbugs:jsr305")
-	testCompile("org.xmlunit:xmlunit-assertj")
-	testCompile("org.xmlunit:xmlunit-matchers")
+	testCompile("javax.annotation:javax.annotation-api")
 	testCompile("javax.xml.bind:jaxb-api")
 	testCompile("com.fasterxml.woodstox:woodstox-core")
+	testCompile("org.xmlunit:xmlunit-assertj")
+	testCompile("org.xmlunit:xmlunit-matchers")
 	testCompile(project(":kotlin-coroutines"))
 	testCompile("io.projectreactor.tools:blockhound")
-	testFixturesImplementation("com.google.code.findbugs:jsr305")
 	testFixturesImplementation("io.projectreactor:reactor-test")
-	testFixturesImplementation("org.assertj:assertj-core")
+	testFixturesImplementation("com.google.code.findbugs:jsr305")
 	testFixturesImplementation("org.junit.platform:junit-platform-launcher")
 	testFixturesImplementation("org.junit.jupiter:junit-jupiter-api")
 	testFixturesImplementation("org.junit.jupiter:junit-jupiter-params")
+	testFixturesImplementation("org.assertj:assertj-core")
 	testFixturesImplementation("org.xmlunit:xmlunit-assertj")
 }

@@ -99,7 +99,7 @@ jar {
 }

 test {
-	// make sure the classes dir is used on the test classpath (required by ResourceTests)
+	// Make sure the classes dir is used on the test classpath (required by ResourceTests)
 	// When test fixtures are involved, the JAR is used by default
 	classpath = sourceSets.main.output.classesDirs + classpath - files(jar.archiveFile)
-}
+}
@@ -0,0 +1,110 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.core.codec;
+
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.infra.Blackhole;
+import reactor.core.publisher.Flux;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.core.io.buffer.DataBuffer;
+import org.springframework.core.io.buffer.DataBufferFactory;
+import org.springframework.core.io.buffer.DataBufferUtils;
+import org.springframework.core.io.buffer.DefaultDataBufferFactory;
+import org.springframework.util.MimeType;
+
+/**
+ * Benchmarks for {@link DataBufferUtils}.
+ *
+ * @author Rossen Stoyanchev
+ */
+@BenchmarkMode(Mode.Throughput)
+public class StringDecoderBenchmark {
+
+	@Benchmark
+	public void parseSseLines(SseLinesState state, Blackhole blackhole) {
+		blackhole.consume(state.parseLines().blockLast());
+	}
+
+
+	@State(Scope.Benchmark)
+	@SuppressWarnings({"NotNullFieldNotInitialized", "ConstantConditions"})
+	public static class SseLinesState {
+
+		private static final Charset CHARSET = StandardCharsets.UTF_8;
+
+		private static final ResolvableType ELEMENT_TYPE = ResolvableType.forClass(String.class);
+
+
+		@Param("10240")
+		int totalSize;
+
+		@Param("2000")
+		int chunkSize;
+
+		List<DataBuffer> chunks;
+
+		StringDecoder decoder = StringDecoder.textPlainOnly(Arrays.asList("\r\n", "\n"), false);
+
+		MimeType mimeType = new MimeType("text", "plain", CHARSET);
+
+
+		@Setup(Level.Trial)
+		public void setup() {
+			String eventTemplate = "id:$1\n" +
+					"event:some-event\n" +
+					":some-comment-$1-aa\n" +
+					":some-comment-$1-bb\n" +
+					"data:abcdefg-$1-hijklmnop-$1-qrstuvw-$1-xyz-$1\n\n";
+
+			int eventLength = String.format(eventTemplate, String.format("%05d", 1)).length();
+			int eventCount = this.totalSize / eventLength;
+			DataBufferFactory bufferFactory = new DefaultDataBufferFactory();
+
+			this.chunks = Flux.range(1, eventCount)
+					.map(index -> String.format(eventTemplate, String.format("%05d", index)))
+					.buffer(this.chunkSize > eventLength ? this.chunkSize / eventLength : 1)
+					.map(strings -> String.join("", strings))
+					.map(chunk -> {
+						byte[] bytes = chunk.getBytes(CHARSET);
+						DataBuffer buffer = bufferFactory.allocateBuffer(bytes.length);
+						buffer.write(bytes);
+						return buffer;
+					})
+					.collectList()
+					.block();
+		}
+
+		public Flux<String> parseLines() {
+			Flux<DataBuffer> input = Flux.fromIterable(this.chunks).doOnNext(DataBufferUtils::retain);
+			return this.decoder.decode(input, ELEMENT_TYPE, this.mimeType, Collections.emptyMap());
+		}
+	}
+
+}
@@ -53,7 +53,7 @@ public interface Opcodes {
  /**
   * <i>Experimental, use at your own risk. This field will be renamed when it becomes stable, this
   * will break existing code using it. Only code compiled with --enable-preview can use this.</i>
-   * <p>SPRING PATCH: no preview mode check for ASM 9 experimental, enabling it by default.
+   * <p>SPRING PATCH: no preview mode check for ASM 10 experimental, enabling it by default.
   */
  int ASM10_EXPERIMENTAL = 1 << 24 | 10 << 16 | 0 << 8;

@@ -21,10 +21,10 @@ import org.springframework.asm.Opcodes;
 final class AsmApi {

    /**
-     * SPRING PATCH: always returns ASM7.
+     * SPRING PATCH: always returns ASM9.
     */
    static int value() {
-        return Opcodes.ASM7;
+        return Opcodes.ASM9;
    }

    private AsmApi() {
@@ -77,7 +77,6 @@ public abstract class KotlinDetector {

 	/**
 	 * Return {@code true} if the method is a suspending function.
-	 * @author Sebastien Deleuze
 	 * @since 5.3
 	 */
 	public static boolean isSuspendingFunction(Method method) {
@@ -264,14 +264,12 @@ public class ReactiveAdapterRegistry {
 			registry.registerReactiveType(
 					ReactiveTypeDescriptor.multiValue(io.reactivex.Observable.class, io.reactivex.Observable::empty),
 					source -> ((io.reactivex.Observable<?>) source).toFlowable(io.reactivex.BackpressureStrategy.BUFFER),
-					source -> io.reactivex.Flowable.fromPublisher(source)
-							.toObservable()
+					io.reactivex.Observable::fromPublisher
 			);
 			registry.registerReactiveType(
 					ReactiveTypeDescriptor.singleRequiredValue(io.reactivex.Single.class),
 					source -> ((io.reactivex.Single<?>) source).toFlowable(),
-					source -> io.reactivex.Flowable.fromPublisher(source)
-							.toObservable().singleElement().toSingle()
+					io.reactivex.Single::fromPublisher
 			);
 			registry.registerReactiveType(
 					ReactiveTypeDescriptor.singleOptionalValue(io.reactivex.Maybe.class, io.reactivex.Maybe::empty),
@@ -282,8 +280,7 @@ public class ReactiveAdapterRegistry {
 			registry.registerReactiveType(
 					ReactiveTypeDescriptor.noValue(io.reactivex.Completable.class, io.reactivex.Completable::complete),
 					source -> ((io.reactivex.Completable) source).toFlowable(),
-					source -> io.reactivex.Flowable.fromPublisher(source)
-							.toObservable().ignoreElements()
+					io.reactivex.Completable::fromPublisher
 			);
 		}
 	}
@@ -304,30 +301,26 @@ public class ReactiveAdapterRegistry {
 							io.reactivex.rxjava3.core.Observable::empty),
 					source -> ((io.reactivex.rxjava3.core.Observable<?>) source).toFlowable(
 							io.reactivex.rxjava3.core.BackpressureStrategy.BUFFER),
-					source -> io.reactivex.rxjava3.core.Flowable.fromPublisher(source)
-							.toObservable()
+					io.reactivex.rxjava3.core.Observable::fromPublisher
 			);
 			registry.registerReactiveType(
 					ReactiveTypeDescriptor.singleRequiredValue(io.reactivex.rxjava3.core.Single.class),
 					source -> ((io.reactivex.rxjava3.core.Single<?>) source).toFlowable(),
-					source -> io.reactivex.rxjava3.core.Flowable.fromPublisher(source)
-							.toObservable().singleElement().toSingle()
+					io.reactivex.rxjava3.core.Single::fromPublisher
 			);
 			registry.registerReactiveType(
 					ReactiveTypeDescriptor.singleOptionalValue(
 							io.reactivex.rxjava3.core.Maybe.class,
 							io.reactivex.rxjava3.core.Maybe::empty),
 					source -> ((io.reactivex.rxjava3.core.Maybe<?>) source).toFlowable(),
-					source -> io.reactivex.rxjava3.core.Flowable.fromPublisher(source)
-							.toObservable().singleElement()
+					io.reactivex.rxjava3.core.Maybe::fromPublisher
 			);
 			registry.registerReactiveType(
 					ReactiveTypeDescriptor.noValue(
 							io.reactivex.rxjava3.core.Completable.class,
 							io.reactivex.rxjava3.core.Completable::complete),
 					source -> ((io.reactivex.rxjava3.core.Completable) source).toFlowable(),
-					source -> io.reactivex.rxjava3.core.Flowable.fromPublisher(source)
-							.toObservable().ignoreElements()
+					io.reactivex.rxjava3.core.Completable::fromPublisher
 			);
 		}
 	}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -18,8 +18,8 @@ package org.springframework.core.annotation;

 import java.lang.annotation.Annotation;
 import java.util.ArrayList;
+import java.util.Collection;
 import java.util.LinkedHashSet;
-import java.util.List;
 import java.util.Set;
 import java.util.function.Function;
 import java.util.function.IntFunction;
@@ -31,10 +31,11 @@ import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;

 /**
- * Collector implementations that provide various reduction operations for
+ * {@link Collector} implementations that provide various reduction operations for
 * {@link MergedAnnotation} instances.
 *
 * @author Phillip Webb
+ * @author Sam Brannen
 * @since 5.2
 */
 public abstract class MergedAnnotationCollectors {
@@ -52,13 +53,16 @@ public abstract class MergedAnnotationCollectors {
 	 * Create a new {@link Collector} that accumulates merged annotations to a
 	 * {@link LinkedHashSet} containing {@linkplain MergedAnnotation#synthesize()
 	 * synthesized} versions.
+	 * <p>The collector returned by this method is effectively equivalent to
+	 * {@code Collectors.mapping(MergedAnnotation::synthesize, Collectors.toCollection(LinkedHashSet::new))}
+	 * but avoids the creation of a composite collector.
 	 * @param <A> the annotation type
 	 * @return a {@link Collector} which collects and synthesizes the
 	 * annotations into a {@link Set}
 	 */
 	public static <A extends Annotation> Collector<MergedAnnotation<A>, ?, Set<A>> toAnnotationSet() {
-		return Collector.of(ArrayList<A>::new, (list, annotation) -> list.add(annotation.synthesize()),
-				MergedAnnotationCollectors::addAll, LinkedHashSet::new);
+		return Collector.of(LinkedHashSet::new, (set, annotation) -> set.add(annotation.synthesize()),
+				MergedAnnotationCollectors::combiner);
 	}

 	/**
@@ -90,14 +94,14 @@ public abstract class MergedAnnotationCollectors {
 			IntFunction<R[]> generator) {

 		return Collector.of(ArrayList::new, (list, annotation) -> list.add(annotation.synthesize()),
-				MergedAnnotationCollectors::addAll, list -> list.toArray(generator.apply(list.size())));
+				MergedAnnotationCollectors::combiner, list -> list.toArray(generator.apply(list.size())));
 	}

 	/**
-	 * Create a new {@link Collector} that accumulates merged annotations to an
+	 * Create a new {@link Collector} that accumulates merged annotations to a
 	 * {@link MultiValueMap} with items {@linkplain MultiValueMap#add(Object, Object)
 	 * added} from each merged annotation
-	 * {@link MergedAnnotation#asMap(Adapt...) as a map}.
+	 * {@linkplain MergedAnnotation#asMap(Adapt...) as a map}.
 	 * @param <A> the annotation type
 	 * @param adaptations the adaptations that should be applied to the annotation values
 	 * @return a {@link Collector} which collects and synthesizes the
@@ -111,13 +115,13 @@ public abstract class MergedAnnotationCollectors {
 	}

 	/**
-	 * Create a new {@link Collector} that accumulates merged annotations to an
+	 * Create a new {@link Collector} that accumulates merged annotations to a
 	 * {@link MultiValueMap} with items {@linkplain MultiValueMap#add(Object, Object)
 	 * added} from each merged annotation
-	 * {@link MergedAnnotation#asMap(Adapt...) as a map}.
+	 * {@linkplain MergedAnnotation#asMap(Adapt...) as a map}.
 	 * @param <A> the annotation type
-	 * @param adaptations the adaptations that should be applied to the annotation values
 	 * @param finisher the finisher function for the new {@link MultiValueMap}
+	 * @param adaptations the adaptations that should be applied to the annotation values
 	 * @return a {@link Collector} which collects and synthesizes the
 	 * annotations into a {@link LinkedMultiValueMap}
 	 * @see #toMultiValueMap(MergedAnnotation.Adapt...)
@@ -130,7 +134,7 @@ public abstract class MergedAnnotationCollectors {
 				IDENTITY_FINISH_CHARACTERISTICS : NO_CHARACTERISTICS);
 		return Collector.of(LinkedMultiValueMap::new,
 				(map, annotation) -> annotation.asMap(adaptations).forEach(map::add),
-				MergedAnnotationCollectors::merge, finisher, characteristics);
+				MergedAnnotationCollectors::combiner, finisher, characteristics);
 	}


@@ -138,13 +142,22 @@ public abstract class MergedAnnotationCollectors {
 		return instance == candidate;
 	}

-	private static <E, L extends List<E>> L addAll(L list, L additions) {
-		list.addAll(additions);
-		return list;
+	/**
+	 * {@link Collector#combiner() Combiner} for collections.
+	 * <p>This method is only invoked if the {@link java.util.stream.Stream} is
+	 * processed in {@linkplain java.util.stream.Stream#parallel() parallel}.
+	 */
+	private static <E, C extends Collection<E>> C combiner(C collection, C additions) {
+		collection.addAll(additions);
+		return collection;
 	}

-	private static <K, V> MultiValueMap<K, V> merge(MultiValueMap<K, V> map,
-			MultiValueMap<K, V> additions) {
+	/**
+	 * {@link Collector#combiner() Combiner} for multi-value maps.
+	 * <p>This method is only invoked if the {@link java.util.stream.Stream} is
+	 * processed in {@linkplain java.util.stream.Stream#parallel() parallel}.
+	 */
+	private static <K, V> MultiValueMap<K, V> combiner(MultiValueMap<K, V> map, MultiValueMap<K, V> additions) {
 		map.addAll(additions);
 		return map;
 	}
@@ -21,21 +21,20 @@ import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
-import java.util.function.Consumer;

 import org.reactivestreams.Publisher;
 import reactor.core.publisher.Flux;
+import reactor.core.publisher.Mono;

 import org.springframework.core.ResolvableType;
 import org.springframework.core.io.buffer.DataBuffer;
-import org.springframework.core.io.buffer.DataBufferLimitException;
 import org.springframework.core.io.buffer.DataBufferUtils;
-import org.springframework.core.io.buffer.DataBufferWrapper;
-import org.springframework.core.io.buffer.DefaultDataBufferFactory;
 import org.springframework.core.io.buffer.LimitedDataBufferList;
 import org.springframework.core.io.buffer.PooledDataBuffer;
 import org.springframework.core.log.LogFormatUtils;
@@ -45,12 +44,12 @@ import org.springframework.util.MimeType;
 import org.springframework.util.MimeTypeUtils;

 /**
- * Decode from a data buffer stream to a {@code String} stream. Before decoding, this decoder
- * realigns the incoming data buffers so that each buffer ends with a newline.
- * This is to make sure that multibyte characters are decoded properly, and do not cross buffer
- * boundaries. The default delimiters ({@code \n}, {@code \r\n})can be customized.
- *
- * <p>Partially inspired by Netty's {@code DelimiterBasedFrameDecoder}.
+ * Decode from a data buffer stream to a {@code String} stream, either splitting
+ * or aggregating incoming data chunks to realign along newlines delimiters
+ * and produce a stream of strings. This is useful for streaming but is also
+ * necessary to ensure that that multibyte characters can be decoded correctly,
+ * avoiding split-character issues. The default delimiters used by default are
+ * {@code \n} and {@code \r\n} but that can be customized.
 *
 * @author Sebastien Deleuze
 * @author Brian Clozel
@@ -115,21 +114,22 @@ public final class StringDecoder extends AbstractDataBufferDecoder<String> {

 		byte[][] delimiterBytes = getDelimiterBytes(mimeType);

-		Flux<DataBuffer> inputFlux = Flux.defer(() -> {
-			DataBufferUtils.Matcher matcher = DataBufferUtils.matcher(delimiterBytes);
+		LimitedDataBufferList chunks = new LimitedDataBufferList(getMaxInMemorySize());
+		DataBufferUtils.Matcher matcher = DataBufferUtils.matcher(delimiterBytes);

-			@SuppressWarnings("MismatchedQueryAndUpdateOfCollection")
-			LimitChecker limiter = new LimitChecker(getMaxInMemorySize());
-
-			return Flux.from(input)
-					.concatMapIterable(buffer -> endFrameAfterDelimiter(buffer, matcher))
-					.doOnNext(limiter)
-					.bufferUntil(buffer -> buffer instanceof EndFrameBuffer)
-					.map(list -> joinAndStrip(list, this.stripDelimiter))
-					.doOnDiscard(PooledDataBuffer.class, DataBufferUtils::release);
-		});
-
-		return super.decode(inputFlux, elementType, mimeType, hints);
+		return Flux.from(input)
+				.concatMapIterable(buffer -> processDataBuffer(buffer, matcher, chunks))
+				.concatWith(Mono.defer(() -> {
+					if (chunks.isEmpty()) {
+						return Mono.empty();
+					}
+					DataBuffer lastBuffer = chunks.get(0).factory().join(chunks);
+					chunks.clear();
+					return Mono.just(lastBuffer);
+				}))
+				.doOnTerminate(chunks::releaseAndClear)
+				.doOnDiscard(PooledDataBuffer.class, PooledDataBuffer::release)
+				.map(buffer -> decode(buffer, elementType, mimeType, hints));
 	}

 	private byte[][] getDelimiterBytes(@Nullable MimeType mimeType) {
@@ -142,6 +142,43 @@ public final class StringDecoder extends AbstractDataBufferDecoder<String> {
 		});
 	}

+	private Collection<DataBuffer> processDataBuffer(
+			DataBuffer buffer, DataBufferUtils.Matcher matcher, LimitedDataBufferList chunks) {
+
+		try {
+			List<DataBuffer> result = null;
+			do {
+				int endIndex = matcher.match(buffer);
+				if (endIndex == -1) {
+					chunks.add(buffer);
+					DataBufferUtils.retain(buffer); // retain after add (may raise DataBufferLimitException)
+					break;
+				}
+				int startIndex = buffer.readPosition();
+				int length = (endIndex - startIndex + 1);
+				DataBuffer slice = buffer.retainedSlice(startIndex, length);
+				if (this.stripDelimiter) {
+					slice.writePosition(slice.writePosition() - matcher.delimiter().length);
+				}
+				result = (result != null ? result : new ArrayList<>());
+				if (chunks.isEmpty()) {
+					result.add(slice);
+				}
+				else {
+					chunks.add(slice);
+					result.add(buffer.factory().join(chunks));
+					chunks.clear();
+				}
+				buffer.readPosition(endIndex + 1);
+			}
+			while (buffer.readableByteCount() > 0);
+			return (result != null ? result : Collections.emptyList());
+		}
+		finally {
+			DataBufferUtils.release(buffer);
+		}
+	}
+
 	@Override
 	public String decode(DataBuffer dataBuffer, ResolvableType elementType,
 			@Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {
@@ -166,68 +203,6 @@ public final class StringDecoder extends AbstractDataBufferDecoder<String> {
 		}
 	}

-	/**
-	 * Finds the first match and longest delimiter, {@link EndFrameBuffer} just after it.
-	 * @param dataBuffer the buffer to find delimiters in
-	 * @param matcher used to find the first delimiters
-	 * @return a flux of buffers, containing {@link EndFrameBuffer} after each delimiter that was
-	 * found in {@code dataBuffer}. Returns  Flux, because returning List (w/ flatMapIterable)
-	 * results in memory leaks due to pre-fetching.
-	 */
-	private static List<DataBuffer> endFrameAfterDelimiter(DataBuffer dataBuffer, DataBufferUtils.Matcher matcher) {
-		List<DataBuffer> result = new ArrayList<>();
-		try {
-			do {
-				int endIdx = matcher.match(dataBuffer);
-				if (endIdx != -1) {
-					int readPosition = dataBuffer.readPosition();
-					int length = (endIdx - readPosition + 1);
-					DataBuffer slice = dataBuffer.retainedSlice(readPosition, length);
-					result.add(slice);
-					result.add(new EndFrameBuffer(matcher.delimiter()));
-					dataBuffer.readPosition(endIdx + 1);
-				}
-				else {
-					result.add(DataBufferUtils.retain(dataBuffer));
-					break;
-				}
-			}
-			while (dataBuffer.readableByteCount() > 0);
-		}
-		finally {
-			DataBufferUtils.release(dataBuffer);
-		}
-		return result;
-	}
-
-	/**
-	 * Joins the given list of buffers. If the list ends with a {@link EndFrameBuffer}, it is
-	 * removed. If {@code stripDelimiter} is {@code true} and the resulting buffer ends with
-	 * a delimiter, it is removed.
-	 * @param dataBuffers the data buffers to join
-	 * @param stripDelimiter whether to strip the delimiter
-	 * @return the joined buffer
-	 */
-	private static DataBuffer joinAndStrip(List<DataBuffer> dataBuffers, boolean stripDelimiter) {
-		Assert.state(!dataBuffers.isEmpty(), "DataBuffers should not be empty");
-
-		byte[] matchingDelimiter = null;
-
-		int lastIdx = dataBuffers.size() - 1;
-		DataBuffer lastBuffer = dataBuffers.get(lastIdx);
-		if (lastBuffer instanceof EndFrameBuffer) {
-			matchingDelimiter = ((EndFrameBuffer) lastBuffer).delimiter();
-			dataBuffers.remove(lastIdx);
-		}
-
-		DataBuffer result = dataBuffers.get(0).factory().join(dataBuffers);
-		if (stripDelimiter && matchingDelimiter != null) {
-			result.writePosition(result.writePosition() - matchingDelimiter.length);
-		}
-		return result;
-	}
-
-
 	/**
 	 * Create a {@code StringDecoder} for {@code "text/plain"}.
 	 * @param stripDelimiter this flag is ignored
@@ -285,46 +260,4 @@ public final class StringDecoder extends AbstractDataBufferDecoder<String> {
 				new MimeType("text", "plain", DEFAULT_CHARSET), MimeTypeUtils.ALL);
 	}

-
-	private static class EndFrameBuffer extends DataBufferWrapper {
-
-		private static final DataBuffer BUFFER = DefaultDataBufferFactory.sharedInstance.wrap(new byte[0]);
-
-		private final byte[] delimiter;
-
-		public EndFrameBuffer(byte[] delimiter) {
-			super(BUFFER);
-			this.delimiter = delimiter;
-		}
-
-		public byte[] delimiter() {
-			return this.delimiter;
-		}
-	}
-
-
-	private static class LimitChecker implements Consumer<DataBuffer> {
-
-		@SuppressWarnings("MismatchedQueryAndUpdateOfCollection")
-		private final LimitedDataBufferList list;
-
-		LimitChecker(int maxInMemorySize) {
-			this.list = new LimitedDataBufferList(maxInMemorySize);
-		}
-
-		@Override
-		public void accept(DataBuffer buffer) {
-			if (buffer instanceof EndFrameBuffer) {
-				this.list.clear();
-			}
-			try {
-				this.list.add(buffer);
-			}
-			catch (DataBufferLimitException ex) {
-				DataBufferUtils.release(buffer);
-				throw ex;
-			}
-		}
-	}
-
 }
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -118,7 +118,7 @@ public final class Property {
 	}


-	// package private
+	// Package private

 	MethodParameter getMethodParameter() {
 		return this.methodParameter;
@@ -132,7 +132,7 @@ public final class Property {
 	}


-	// internal helpers
+	// Internal helpers

 	private String resolveName() {
 		if (this.readMethod != null) {
@@ -142,10 +142,13 @@ public final class Property {
 			}
 			else {
 				index = this.readMethod.getName().indexOf("is");
-				if (index == -1) {
-					throw new IllegalArgumentException("Not a getter method");
+				if (index != -1) {
+					index += 2;
+				}
+				else {
+					// Record-style plain accessor method, e.g. name()
+					index = 0;
 				}
-				index += 2;
 			}
 			return StringUtils.uncapitalize(this.readMethod.getName().substring(index));
 		}
@@ -30,7 +30,6 @@ import java.nio.channels.WritableByteChannel;
 import java.nio.file.OpenOption;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
-import java.util.Arrays;
 import java.util.HashSet;
 import java.util.Set;
 import java.util.concurrent.Callable;
@@ -568,65 +567,290 @@ public abstract class DataBufferUtils {

 	/**
 	 * Return a {@link Matcher} for the given delimiter.
-	 * The matcher can be used to find the delimiters in data buffers.
+	 * The matcher can be used to find the delimiters in a stream of data buffers.
 	 * @param delimiter the delimiter bytes to find
 	 * @return the matcher
 	 * @since 5.2
 	 */
 	public static Matcher matcher(byte[] delimiter) {
-		Assert.isTrue(delimiter.length > 0, "Delimiter must not be empty");
-		return new KnuthMorrisPrattMatcher(delimiter);
+		return createMatcher(delimiter);
 	}

-	/** Return a {@link Matcher} for the given delimiters.
-	 * The matcher can be used to find the delimiters in data buffers.
+	/**
+	 * Return a {@link Matcher} for the given delimiters.
+	 * The matcher can be used to find the delimiters in a stream of data buffers.
 	 * @param delimiters the delimiters bytes to find
 	 * @return the matcher
 	 * @since 5.2
 	 */
 	public static Matcher matcher(byte[]... delimiters) {
 		Assert.isTrue(delimiters.length > 0, "Delimiters must not be empty");
-		if (delimiters.length == 1) {
-			return matcher(delimiters[0]);
-		}
-		else {
-			Matcher[] matchers = new Matcher[delimiters.length];
-			for (int i = 0; i < delimiters.length; i++) {
-				matchers[i] = matcher(delimiters[i]);
-			}
-			return new CompositeMatcher(matchers);
+		return (delimiters.length == 1 ? createMatcher(delimiters[0]) : new CompositeMatcher(delimiters));
+	}
+
+	private static NestedMatcher createMatcher(byte[] delimiter) {
+		Assert.isTrue(delimiter.length > 0, "Delimiter must not be empty");
+		switch (delimiter.length) {
+			case 1:
+				return (delimiter[0] == 10 ? SingleByteMatcher.NEWLINE_MATCHER : new SingleByteMatcher(delimiter));
+			case 2:
+				return new TwoByteMatcher(delimiter);
+			default:
+				return new KnuthMorrisPrattMatcher(delimiter);
 		}
 	}


 	/**
-	 * Defines an object that matches a data buffer against a delimiter.
+	 * Contract to find delimiter(s) against one or more data buffers that can
+	 * be passed one at a time to the {@link #match(DataBuffer)} method.
+	 *
 	 * @since 5.2
 	 * @see #match(DataBuffer)
 	 */
 	public interface Matcher {

 		/**
-		 * Returns the position of the final matching delimiter byte that matches the given buffer,
-		 * or {@code -1} if not found.
-		 * @param dataBuffer the buffer in which to search for the delimiter
-		 * @return the position of the final matching delimiter, or {@code -1} if not found.
+		 * Find the first matching delimiter and return the index of the last
+		 * byte of the delimiter, or {@code -1} if not found.
 		 */
 		int match(DataBuffer dataBuffer);

 		/**
-		 * Return the delimiter used for this matcher.
-		 * @return the delimiter
+		 * Return the delimiter from the last invocation of {@link #match(DataBuffer)}.
 		 */
 		byte[] delimiter();

 		/**
-		 * Resets the state of this matcher.
+		 * Reset the state of this matcher.
 		 */
 		void reset();
 	}


+	/**
+	 * Matcher that supports searching for multiple delimiters.
+	 */
+	private static class CompositeMatcher implements Matcher {
+
+		private static final byte[] NO_DELIMITER = new byte[0];
+
+
+		private final NestedMatcher[] matchers;
+
+		byte[] longestDelimiter = NO_DELIMITER;
+
+		CompositeMatcher(byte[][] delimiters) {
+			this.matchers = initMatchers(delimiters);
+		}
+
+		private static NestedMatcher[] initMatchers(byte[][] delimiters) {
+			NestedMatcher[] matchers = new NestedMatcher[delimiters.length];
+			for (int i = 0; i < delimiters.length; i++) {
+				matchers[i] = createMatcher(delimiters[i]);
+			}
+			return matchers;
+		}
+
+		@Override
+		public int match(DataBuffer dataBuffer) {
+			this.longestDelimiter = NO_DELIMITER;
+
+			for (int pos = dataBuffer.readPosition(); pos < dataBuffer.writePosition(); pos++) {
+				byte b = dataBuffer.getByte(pos);
+
+				for (NestedMatcher matcher : this.matchers) {
+					if (matcher.match(b) && matcher.delimiter().length > this.longestDelimiter.length) {
+						this.longestDelimiter = matcher.delimiter();
+					}
+				}
+
+				if (this.longestDelimiter != NO_DELIMITER) {
+					reset();
+					return pos;
+				}
+			}
+			return -1;
+		}
+
+		@Override
+		public byte[] delimiter() {
+			Assert.state(this.longestDelimiter != NO_DELIMITER, "Illegal state!");
+			return this.longestDelimiter;
+		}
+
+		@Override
+		public void reset() {
+			for (NestedMatcher matcher : this.matchers) {
+				matcher.reset();
+			}
+		}
+	}
+
+
+	/**
+	 * Matcher that can be nested within {@link CompositeMatcher} where multiple
+	 * matchers advance together using the same index, one byte at a time.
+	 */
+	private interface NestedMatcher extends Matcher {
+
+		/**
+		 * Perform a match against the next byte of the stream and return true
+		 * if the delimiter is fully matched.
+		 */
+		boolean match(byte b);
+
+	}
+
+
+	/**
+	 * Matcher for a single byte delimiter.
+	 */
+	private static class SingleByteMatcher implements NestedMatcher {
+
+		static SingleByteMatcher NEWLINE_MATCHER = new SingleByteMatcher(new byte[] {10});
+
+		private final byte[] delimiter;
+
+		SingleByteMatcher(byte[] delimiter) {
+			Assert.isTrue(delimiter.length == 1, "Expected a 1 byte delimiter");
+			this.delimiter = delimiter;
+		}
+
+		@Override
+		public int match(DataBuffer dataBuffer) {
+			for (int pos = dataBuffer.readPosition(); pos < dataBuffer.writePosition(); pos++) {
+				byte b = dataBuffer.getByte(pos);
+				if (match(b)) {
+					return pos;
+				}
+			}
+			return -1;
+		}
+
+		@Override
+		public boolean match(byte b) {
+			return this.delimiter[0] == b;
+		}
+
+		@Override
+		public byte[] delimiter() {
+			return this.delimiter;
+		}
+
+		@Override
+		public void reset() {
+		}
+	}
+
+
+	/**
+	 * Base class for a {@link NestedMatcher}.
+	 */
+	private static abstract class AbstractNestedMatcher implements NestedMatcher {
+
+		private final byte[] delimiter;
+
+		private int matches = 0;
+
+
+		protected AbstractNestedMatcher(byte[] delimiter) {
+			this.delimiter = delimiter;
+		}
+
+		protected void setMatches(int index) {
+			this.matches = index;
+		}
+
+		protected int getMatches() {
+			return this.matches;
+		}
+
+		@Override
+		public int match(DataBuffer dataBuffer) {
+			for (int pos = dataBuffer.readPosition(); pos < dataBuffer.writePosition(); pos++) {
+				byte b = dataBuffer.getByte(pos);
+				if (match(b)) {
+					reset();
+					return pos;
+				}
+			}
+			return -1;
+		}
+
+		@Override
+		public boolean match(byte b) {
+			if (b == this.delimiter[this.matches]) {
+				this.matches++;
+				return (this.matches == delimiter().length);
+			}
+			return false;
+		}
+
+		@Override
+		public byte[] delimiter() {
+			return this.delimiter;
+		}
+
+		@Override
+		public void reset() {
+			this.matches = 0;
+		}
+	}
+
+
+	/**
+	 * Matcher with a 2 byte delimiter that does not benefit from a
+	 * Knuth-Morris-Pratt suffix-prefix table.
+	 */
+	private static class TwoByteMatcher extends AbstractNestedMatcher {
+
+		protected TwoByteMatcher(byte[] delimiter) {
+			super(delimiter);
+			Assert.isTrue(delimiter.length == 2, "Expected a 2-byte delimiter");
+		}
+	}
+
+
+	/**
+	 * Implementation of {@link Matcher} that uses the Knuth-Morris-Pratt algorithm.
+	 * @see <a href="https://www.nayuki.io/page/knuth-morris-pratt-string-matching">Knuth-Morris-Pratt string matching</a>
+	 */
+	private static class KnuthMorrisPrattMatcher extends AbstractNestedMatcher {
+
+		private final int[] table;
+
+		public KnuthMorrisPrattMatcher(byte[] delimiter) {
+			super(delimiter);
+			this.table = longestSuffixPrefixTable(delimiter);
+		}
+
+		private static int[] longestSuffixPrefixTable(byte[] delimiter) {
+			int[] result = new int[delimiter.length];
+			result[0] = 0;
+			for (int i = 1; i < delimiter.length; i++) {
+				int j = result[i - 1];
+				while (j > 0 && delimiter[i] != delimiter[j]) {
+					j = result[j - 1];
+				}
+				if (delimiter[i] == delimiter[j]) {
+					j++;
+				}
+				result[i] = j;
+			}
+			return result;
+		}
+
+		@Override
+		public boolean match(byte b) {
+			while (getMatches() > 0 && b != delimiter()[getMatches()]) {
+				setMatches(this.table[getMatches() - 1]);
+			}
+			return super.match(b);
+		}
+	}
+
+
 	private static class ReadableByteChannelGenerator implements Consumer<SynchronousSink<DataBuffer>> {

 		private final ReadableByteChannel channel;
@@ -683,9 +907,7 @@ public abstract class DataBufferUtils {

 		private final AtomicLong position;

-		private final AtomicBoolean reading = new AtomicBoolean();
-
-		private final AtomicBoolean disposed = new AtomicBoolean();
+		private final AtomicReference<State> state = new AtomicReference<>(State.IDLE);

 		public ReadCompletionHandler(AsynchronousFileChannel channel,
 				FluxSink<DataBuffer> sink, long position, DataBufferFactory dataBufferFactory, int bufferSize) {
@@ -697,39 +919,68 @@ public abstract class DataBufferUtils {
 			this.bufferSize = bufferSize;
 		}

-		public void read() {
-			if (this.sink.requestedFromDownstream() > 0 &&
-					isNotDisposed() &&
-					this.reading.compareAndSet(false, true)) {
-				DataBuffer dataBuffer = this.dataBufferFactory.allocateBuffer(this.bufferSize);
-				ByteBuffer byteBuffer = dataBuffer.asByteBuffer(0, this.bufferSize);
-				this.channel.read(byteBuffer, this.position.get(), dataBuffer, this);
+		/**
+		 * Invoked when Reactive Streams consumer signals demand.
+		 */
+		public void request(long n) {
+			tryRead();
+		}
+
+		/**
+		 * Invoked when Reactive Streams consumer cancels.
+		 */
+		public void cancel() {
+			this.state.getAndSet(State.DISPOSED);
+
+			// According java.nio.channels.AsynchronousChannel "if an I/O operation is outstanding
+			// on the channel and the channel's close method is invoked, then the I/O operation
+			// fails with the exception AsynchronousCloseException". That should invoke the failed
+			// callback below and the current DataBuffer should be released.
+
+			closeChannel(this.channel);
+		}
+
+		private void tryRead() {
+			if (this.sink.requestedFromDownstream() > 0 && this.state.compareAndSet(State.IDLE, State.READING)) {
+				read();
 			}
 		}

+		private void read() {
+			DataBuffer dataBuffer = this.dataBufferFactory.allocateBuffer(this.bufferSize);
+			ByteBuffer byteBuffer = dataBuffer.asByteBuffer(0, this.bufferSize);
+			this.channel.read(byteBuffer, this.position.get(), dataBuffer, this);
+		}
+
 		@Override
 		public void completed(Integer read, DataBuffer dataBuffer) {
-			if (isNotDisposed()) {
-				if (read != -1) {
-					this.position.addAndGet(read);
-					dataBuffer.writePosition(read);
-					this.sink.next(dataBuffer);
-					this.reading.set(false);
-					read();
-				}
-				else {
-					release(dataBuffer);
-					closeChannel(this.channel);
-					if (this.disposed.compareAndSet(false, true)) {
-						this.sink.complete();
-					}
-					this.reading.set(false);
-				}
-			}
-			else {
+			if (this.state.get().equals(State.DISPOSED)) {
 				release(dataBuffer);
 				closeChannel(this.channel);
-				this.reading.set(false);
+				return;
+			}
+
+			if (read == -1) {
+				release(dataBuffer);
+				closeChannel(this.channel);
+				this.state.set(State.DISPOSED);
+				this.sink.complete();
+				return;
+			}
+
+			this.position.addAndGet(read);
+			dataBuffer.writePosition(read);
+			this.sink.next(dataBuffer);
+
+			// Stay in READING mode if there is demand
+			if (this.sink.requestedFromDownstream() > 0) {
+				read();
+				return;
+			}
+
+			// Release READING mode and then try again in case of concurrent "request"
+			if (this.state.compareAndSet(State.READING, State.IDLE)) {
+				tryRead();
 			}
 		}

@@ -737,26 +988,12 @@ public abstract class DataBufferUtils {
 		public void failed(Throwable exc, DataBuffer dataBuffer) {
 			release(dataBuffer);
 			closeChannel(this.channel);
-			if (this.disposed.compareAndSet(false, true)) {
-				this.sink.error(exc);
-			}
-			this.reading.set(false);
+			this.state.set(State.DISPOSED);
+			this.sink.error(exc);
 		}

-		public void request(long n) {
-			read();
-		}
-
-		public void cancel() {
-			if (this.disposed.compareAndSet(false, true)) {
-				if (!this.reading.get()) {
-					closeChannel(this.channel);
-				}
-			}
-		}
-
-		private boolean isNotDisposed() {
-			return !this.disposed.get();
+		private enum State {
+			IDLE, READING, DISPOSED
 		}
 	}

@@ -895,124 +1132,4 @@ public abstract class DataBufferUtils {
 		}
 	}

-
-	/**
-	 * Implementation of {@link Matcher} that uses the Knuth-Morris-Pratt algorithm.
-	 * @see <a href="https://www.nayuki.io/page/knuth-morris-pratt-string-matching">Knuth-Morris-Pratt string matching</a>
-	 */
-	private static class KnuthMorrisPrattMatcher implements Matcher {
-
-		private final byte[] delimiter;
-
-		private final int[] table;
-
-		private int matches = 0;
-
-		public KnuthMorrisPrattMatcher(byte[] delimiter) {
-			this.delimiter = Arrays.copyOf(delimiter, delimiter.length);
-			this.table = longestSuffixPrefixTable(delimiter);
-		}
-
-		private static int[] longestSuffixPrefixTable(byte[] delimiter) {
-			int[] result = new int[delimiter.length];
-			result[0] = 0;
-			for (int i = 1; i < delimiter.length; i++) {
-				int j = result[i - 1];
-				while (j > 0 && delimiter[i] != delimiter[j]) {
-					j = result[j - 1];
-				}
-				if (delimiter[i] == delimiter[j]) {
-					j++;
-				}
-				result[i] = j;
-			}
-			return result;
-		}
-
-		@Override
-		public int match(DataBuffer dataBuffer) {
-			for (int i = dataBuffer.readPosition(); i < dataBuffer.writePosition(); i++) {
-				byte b = dataBuffer.getByte(i);
-
-				while (this.matches > 0 && b != this.delimiter[this.matches]) {
-					this.matches = this.table[this.matches - 1];
-				}
-
-				if (b == this.delimiter[this.matches]) {
-					this.matches++;
-					if (this.matches == this.delimiter.length) {
-						reset();
-						return i;
-					}
-				}
-			}
-			return -1;
-		}
-
-		@Override
-		public byte[] delimiter() {
-			return Arrays.copyOf(this.delimiter, this.delimiter.length);
-		}
-
-		@Override
-		public void reset() {
-			this.matches = 0;
-		}
-	}
-
-
-	/**
-	 * Implementation of {@link Matcher} that wraps several other matchers.
-	 */
-	private static class CompositeMatcher implements Matcher {
-
-		private static final byte[] NO_DELIMITER = new byte[0];
-
-		private final Matcher[] matchers;
-
-		byte[] longestDelimiter = NO_DELIMITER;
-
-		public CompositeMatcher(Matcher[] matchers) {
-			this.matchers = matchers;
-		}
-
-		@Override
-		public int match(DataBuffer dataBuffer) {
-			this.longestDelimiter = NO_DELIMITER;
-			int bestEndIdx = Integer.MAX_VALUE;
-
-
-			for (Matcher matcher : this.matchers) {
-				int endIdx = matcher.match(dataBuffer);
-				if (endIdx != -1 &&
-						endIdx <= bestEndIdx &&
-						matcher.delimiter().length > this.longestDelimiter.length) {
-					bestEndIdx = endIdx;
-					this.longestDelimiter = matcher.delimiter();
-				}
-			}
-			if (bestEndIdx == Integer.MAX_VALUE) {
-				this.longestDelimiter = NO_DELIMITER;
-				return -1;
-			}
-			else {
-				reset();
-				return bestEndIdx;
-			}
-		}
-
-		@Override
-		public byte[] delimiter() {
-			Assert.state(this.longestDelimiter != NO_DELIMITER, "Illegal state!");
-			return this.longestDelimiter;
-		}
-
-		@Override
-		public void reset() {
-			for (Matcher matcher : this.matchers) {
-				matcher.reset();
-			}
-		}
-	}
-
 }
@@ -24,10 +24,13 @@ import org.springframework.core.metrics.StartupStep;

 /**
 * {@link ApplicationStartup} implementation for the Java Flight Recorder.
- * <p>This variant records {@link StartupStep} as Flight Recorder events; because such events
- * only support base types, the {@link StartupStep.Tags} are serialized as a single String attribute.
- * <p>Once this is configured on the application context, you can record data by launching the application
- * with recording enabled: {@code java -XX:StartFlightRecording:filename=recording.jfr,duration=10s -jar app.jar}.
+ * <p>This variant records {@link StartupStep} as Flight Recorder events. Because
+ * such events only support base types, the
+ * {@link org.springframework.core.metrics.StartupStep.Tags} are serialized as a
+ * single String attribute.
+ * <p>Once this is configured on the application context, you can record data by
+ * launching the application with recording enabled:
+ * {@code java -XX:StartFlightRecording:filename=recording.jfr,duration=10s -jar app.jar}.
 *
 * @author Brian Clozel
 * @since 5.3
@@ -457,7 +457,6 @@ public abstract class CollectionUtils {
 	 * @since 3.1
 	 */
 	public static <K, V> MultiValueMap<K, V> toMultiValueMap(Map<K, List<V>> targetMap) {
-		Assert.notNull(targetMap, "'targetMap' must not be null");
 		return new MultiValueMapAdapter<>(targetMap);
 	}

@@ -105,17 +105,15 @@ public class ConcurrentLruCache<K, V> {
 			}
 			// Generate value first, to prevent size inconsistency
 			V value = this.generator.apply(key);
-			int cacheSize = this.size;
-			if (cacheSize == this.sizeLimit) {
+			if (this.size == this.sizeLimit) {
 				K leastUsed = this.queue.poll();
 				if (leastUsed != null) {
 					this.cache.remove(leastUsed);
-					cacheSize--;
 				}
 			}
 			this.queue.offer(key);
 			this.cache.put(key, value);
-			this.size = cacheSize + 1;
+			this.size = this.cache.size();
 			return value;
 		}
 		finally {
@@ -123,6 +121,50 @@ public class ConcurrentLruCache<K, V> {
 		}
 	}

+	/**
+	 * Determine whether the given key is present in this cache.
+	 * @param key the key to check for
+	 * @return {@code true} if the key is present,
+	 * {@code false} if there was no matching key
+	 */
+	public boolean contains(K key) {
+		return this.cache.containsKey(key);
+	}
+
+	/**
+	 * Immediately remove the given key and any associated value.
+	 * @param key the key to evict the entry for
+	 * @return {@code true} if the key was present before,
+	 * {@code false} if there was no matching key
+	 */
+	public boolean remove(K key) {
+		this.lock.writeLock().lock();
+		try {
+			boolean wasPresent = (this.cache.remove(key) != null);
+			this.queue.remove(key);
+			this.size = this.cache.size();
+			return wasPresent;
+		}
+		finally {
+			this.lock.writeLock().unlock();
+		}
+	}
+
+	/**
+	 * Immediately remove all entries from this cache.
+	 */
+	public void clear() {
+		this.lock.writeLock().lock();
+		try {
+			this.cache.clear();
+			this.queue.clear();
+			this.size = 0;
+		}
+		finally {
+			this.lock.writeLock().unlock();
+		}
+	}
+
 	/**
 	 * Return the current size of the cache.
 	 * @see #sizeLimit()
@@ -35,7 +35,8 @@ import java.util.Map;
 * @param <K> the key type
 * @param <V> the value element type
 */
-public class LinkedMultiValueMap<K, V> extends MultiValueMapAdapter<K, V> implements Serializable, Cloneable {
+public class LinkedMultiValueMap<K, V> extends MultiValueMapAdapter<K, V>  // new public base class in 5.3
+		implements Serializable, Cloneable {

 	private static final long serialVersionUID = 3801124242820219131L;

@@ -30,23 +30,30 @@ import org.springframework.lang.Nullable;
 *
 * @author Arjen Poutsma
 * @author Juergen Hoeller
- * @since 3.1
+ * @since 5.3
 * @param <K> the key type
 * @param <V> the value element type
 * @see CollectionUtils#toMultiValueMap
 * @see LinkedMultiValueMap
 */
@SuppressWarnings("serial")
-class MultiValueMapAdapter<K, V> implements MultiValueMap<K, V>, Serializable {
+public class MultiValueMapAdapter<K, V> implements MultiValueMap<K, V>, Serializable {

 	private final Map<K, List<V>> targetMap;


-	MultiValueMapAdapter(Map<K, List<V>> targetMap) {
+	/**
+	 * Wrap the given target {@link Map} as a {@link MultiValueMap} adapter.
+	 * @param targetMap the plain target {@code Map}
+	 */
+	public MultiValueMapAdapter(Map<K, List<V>> targetMap) {
+		Assert.notNull(targetMap, "'targetMap' must not be null");
 		this.targetMap = targetMap;
 	}


+	// MultiValueMap implementation
+
 	@Override
 	@Nullable
 	public V getFirst(K key) {
@@ -96,6 +103,9 @@ class MultiValueMapAdapter<K, V> implements MultiValueMap<K, V>, Serializable {
 		return singleValueMap;
 	}

+
+	// Map implementation
+
 	@Override
 	public int size() {
 		return this.targetMap.size();
@@ -128,7 +128,6 @@ public abstract class ObjectUtils {
 	 * @see Optional#isPresent()
 	 * @see ObjectUtils#isEmpty(Object[])
 	 * @see StringUtils#hasLength(CharSequence)
-	 * @see StringUtils#isEmpty(Object)
 	 * @see CollectionUtils#isEmpty(java.util.Collection)
 	 * @see CollectionUtils#isEmpty(java.util.Map)
 	 */
@@ -91,9 +91,10 @@ public abstract class StringUtils {
 	 * {@link #hasLength(String)} or {@link #hasText(String)} instead.</b>
 	 * @param str the candidate object (possibly a {@code String})
 	 * @since 3.2.1
-	 * @see #hasLength(String)
-	 * @see #hasText(String)
+	 * @deprecated as of 5.3, in favor of {@link #hasLength(String)} and
+	 * {@link #hasText(String)} (or {@link ObjectUtils#isEmpty(Object)})
 	 */
+	@Deprecated
 	public static boolean isEmpty(@Nullable Object str) {
 		return (str == null || "".equals(str));
 	}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -89,7 +89,7 @@ class MethodParameterTests {
 		Method method = getClass().getMethod("method", String.class, Long.TYPE);
 		MethodParameter methodParameter = new MethodParameter(method, 0);
 		assertThat(methodParameter.hashCode()).isEqualTo(stringParameter.hashCode());
-		assertThat(methodParameter.hashCode()).isNotEqualTo((long) longParameter.hashCode());
+		assertThat(methodParameter.hashCode()).isNotEqualTo(longParameter.hashCode());
 	}

 	@Test
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -86,7 +86,7 @@ class SynthesizingMethodParameterTests {
 		Method method = getClass().getMethod("method", String.class, Long.TYPE);
 		SynthesizingMethodParameter methodParameter = new SynthesizingMethodParameter(method, 0);
 		assertThat(methodParameter.hashCode()).isEqualTo(stringParameter.hashCode());
-		assertThat(methodParameter.hashCode()).isNotEqualTo((long) longParameter.hashCode());
+		assertThat(methodParameter.hashCode()).isNotEqualTo(longParameter.hashCode());
 	}

 	@Test
@@ -139,20 +139,28 @@ class StringDecoderTests extends AbstractDecoderTests<StringDecoder> {
 	@Test
 	void maxInMemoryLimit() {
 		Flux<DataBuffer> input = Flux.just(
-				stringBuffer("abc\n"), stringBuffer("defg\n"), stringBuffer("hijkl\n"));
+				stringBuffer("abc\n"), stringBuffer("defg\n"),
+				stringBuffer("hi"), stringBuffer("jkl"), stringBuffer("mnop"));

 		this.decoder.setMaxInMemorySize(5);
 		testDecode(input, String.class, step ->
 				step.expectNext("abc", "defg").verifyError(DataBufferLimitException.class));
 	}

-	@Test // gh-24312
-	void maxInMemoryLimitReleaseUnprocessedLinesFromCurrentBuffer() {
+	@Test
+	void maxInMemoryLimitDoesNotApplyToParsedItemsThatDontRequireBuffering() {
 		Flux<DataBuffer> input = Flux.just(
 				stringBuffer("TOO MUCH DATA\nanother line\n\nand another\n"));

 		this.decoder.setMaxInMemorySize(5);
-		testDecode(input, String.class, step -> step.verifyError(DataBufferLimitException.class));
+
+		testDecode(input, String.class, step -> step
+				.expectNext("TOO MUCH DATA")
+				.expectNext("another line")
+				.expectNext("")
+				.expectNext("and another")
+				.expectComplete()
+				.verify());
 	}

 	@Test // gh-24339
@@ -886,18 +886,38 @@ class DataBufferUtilsTests extends AbstractDataBufferAllocatingTests {
 	void matcher2(String displayName, DataBufferFactory bufferFactory) {
 		super.bufferFactory = bufferFactory;

-		DataBuffer foo = stringBuffer("fooobar");
+		DataBuffer foo = stringBuffer("foooobar");

 		byte[] delims = "oo".getBytes(StandardCharsets.UTF_8);
 		DataBufferUtils.Matcher matcher = DataBufferUtils.matcher(delims);
-		int result = matcher.match(foo);
-		assertThat(result).isEqualTo(2);
-		foo.readPosition(2);
-		result = matcher.match(foo);
-		assertThat(result).isEqualTo(3);
-		foo.readPosition(3);
-		result = matcher.match(foo);
-		assertThat(result).isEqualTo(-1);
+		int endIndex = matcher.match(foo);
+		assertThat(endIndex).isEqualTo(2);
+		foo.readPosition(endIndex + 1);
+		endIndex = matcher.match(foo);
+		assertThat(endIndex).isEqualTo(4);
+		foo.readPosition(endIndex + 1);
+		endIndex = matcher.match(foo);
+		assertThat(endIndex).isEqualTo(-1);
+
+		release(foo);
+	}
+
+	@ParameterizedDataBufferAllocatingTest
+	void matcher3(String displayName, DataBufferFactory bufferFactory) {
+		super.bufferFactory = bufferFactory;
+
+		DataBuffer foo = stringBuffer("foooobar");
+
+		byte[] delims = "oo".getBytes(StandardCharsets.UTF_8);
+		DataBufferUtils.Matcher matcher = DataBufferUtils.matcher(delims);
+		int endIndex = matcher.match(foo);
+		assertThat(endIndex).isEqualTo(2);
+		foo.readPosition(endIndex + 1);
+		endIndex = matcher.match(foo);
+		assertThat(endIndex).isEqualTo(4);
+		foo.readPosition(endIndex + 1);
+		endIndex = matcher.match(foo);
+		assertThat(endIndex).isEqualTo(-1);

 		release(foo);
 	}
@@ -0,0 +1,85 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * @author Juergen Hoeller
+ */
+class ConcurrentLruCacheTests {
+
+	private final ConcurrentLruCache<String, String> cache = new ConcurrentLruCache<>(2, key -> key + "value");
+
+
+	@Test
+	void getAndSize() {
+		assertThat(this.cache.sizeLimit()).isEqualTo(2);
+		assertThat(this.cache.size()).isEqualTo(0);
+		assertThat(this.cache.get("k1")).isEqualTo("k1value");
+		assertThat(this.cache.size()).isEqualTo(1);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.get("k2")).isEqualTo("k2value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isTrue();
+		assertThat(this.cache.get("k3")).isEqualTo("k3value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isFalse();
+		assertThat(this.cache.contains("k2")).isTrue();
+		assertThat(this.cache.contains("k3")).isTrue();
+	}
+
+	@Test
+	void removeAndSize() {
+		assertThat(this.cache.get("k1")).isEqualTo("k1value");
+		assertThat(this.cache.get("k2")).isEqualTo("k2value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isTrue();
+		this.cache.remove("k2");
+		assertThat(this.cache.size()).isEqualTo(1);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.get("k3")).isEqualTo("k3value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.contains("k3")).isTrue();
+	}
+
+	@Test
+	void clearAndSize() {
+		assertThat(this.cache.get("k1")).isEqualTo("k1value");
+		assertThat(this.cache.get("k2")).isEqualTo("k2value");
+		assertThat(this.cache.size()).isEqualTo(2);
+		assertThat(this.cache.contains("k1")).isTrue();
+		assertThat(this.cache.contains("k2")).isTrue();
+		this.cache.clear();
+		assertThat(this.cache.size()).isEqualTo(0);
+		assertThat(this.cache.contains("k1")).isFalse();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.get("k3")).isEqualTo("k3value");
+		assertThat(this.cache.size()).isEqualTo(1);
+		assertThat(this.cache.contains("k1")).isFalse();
+		assertThat(this.cache.contains("k2")).isFalse();
+		assertThat(this.cache.contains("k3")).isTrue();
+	}
+
+}
@@ -24,7 +24,6 @@ import org.springframework.expression.spel.CodeFlow;
 import org.springframework.expression.spel.ExpressionState;
 import org.springframework.util.Assert;
 import org.springframework.util.ObjectUtils;
-import org.springframework.util.StringUtils;

 /**
 * Represents the elvis operator ?:. For an expression "a?:b" if a is not null, the value
@@ -52,7 +51,7 @@ public class Elvis extends SpelNodeImpl {
 	public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
 		TypedValue value = this.children[0].getValueInternal(state);
 		// If this check is changed, the generateCode method will need changing too
-		if (!StringUtils.isEmpty(value.getValue())) {
+		if (value.getValue() != null && !"".equals(value.getValue())) {
 			return value;
 		}
 		else {
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -63,34 +63,36 @@ import org.springframework.util.StringUtils;
 * <p>Individual expressions can be compiled by calling {@code SpelCompiler.compile(expression)}.
 *
 * @author Andy Clement
+ * @author Juergen Hoeller
 * @since 4.1
 */
 public final class SpelCompiler implements Opcodes {

-	private static final Log logger = LogFactory.getLog(SpelCompiler.class);
-
 	private static final int CLASSES_DEFINED_LIMIT = 100;

+	private static final Log logger = LogFactory.getLog(SpelCompiler.class);
+
 	// A compiler is created for each classloader, it manages a child class loader of that
 	// classloader and the child is used to load the compiled expressions.
 	private static final Map<ClassLoader, SpelCompiler> compilers = new ConcurrentReferenceHashMap<>();

+
 	// The child ClassLoader used to load the compiled expression classes
-	private ChildClassLoader ccl;
+	private volatile ChildClassLoader childClassLoader;

 	// Counter suffix for generated classes within this SpelCompiler instance
 	private final AtomicInteger suffixId = new AtomicInteger(1);


 	private SpelCompiler(@Nullable ClassLoader classloader) {
-		this.ccl = new ChildClassLoader(classloader);
+		this.childClassLoader = new ChildClassLoader(classloader);
 	}


 	/**
 	 * Attempt compilation of the supplied expression. A check is made to see
 	 * if it is compilable before compilation proceeds. The check involves
-	 * visiting all the nodes in the expression Ast and ensuring enough state
+	 * visiting all the nodes in the expression AST and ensuring enough state
 	 * is known about them that bytecode can be generated for them.
 	 * @param expression the expression to compile
 	 * @return an instance of the class implementing the compiled expression,
@@ -125,7 +127,7 @@ public final class SpelCompiler implements Opcodes {

 	/**
 	 * Generate the class that encapsulates the compiled expression and define it.
-	 * The  generated class will be a subtype of CompiledExpression.
+	 * The generated class will be a subtype of CompiledExpression.
 	 * @param expressionToCompile the expression to be compiled
 	 * @return the expression call, or {@code null} if the decision was to opt out of
 	 * compilation during code generation
@@ -135,7 +137,7 @@ public final class SpelCompiler implements Opcodes {
 		// Create class outline 'spel/ExNNN extends org.springframework.expression.spel.CompiledExpression'
 		String className = "spel/Ex" + getNextSuffix();
 		ClassWriter cw = new ExpressionClassWriter();
-		cw.visit(V1_5, ACC_PUBLIC, className, null, "org/springframework/expression/spel/CompiledExpression", null);
+		cw.visit(V1_8, ACC_PUBLIC, className, null, "org/springframework/expression/spel/CompiledExpression", null);

 		// Create default constructor
 		MethodVisitor mv = cw.visitMethod(ACC_PUBLIC, "<init>", "()V", null, null);
@@ -150,7 +152,7 @@ public final class SpelCompiler implements Opcodes {
 		// Create getValue() method
 		mv = cw.visitMethod(ACC_PUBLIC, "getValue",
 				"(Ljava/lang/Object;Lorg/springframework/expression/EvaluationContext;)Ljava/lang/Object;", null,
-				new String[ ]{"org/springframework/expression/EvaluationException"});
+				new String[] {"org/springframework/expression/EvaluationException"});
 		mv.visitCode();

 		CodeFlow cf = new CodeFlow(className, cw);
@@ -187,7 +189,7 @@ public final class SpelCompiler implements Opcodes {

 	/**
 	 * Load a compiled expression class. Makes sure the classloaders aren't used too much
-	 * because they anchor compiled classes in memory and prevent GC.  If you have expressions
+	 * because they anchor compiled classes in memory and prevent GC. If you have expressions
 	 * continually recompiling over time then by replacing the classloader periodically
 	 * at least some of the older variants can be garbage collected.
 	 * @param name the name of the class
@@ -196,12 +198,25 @@ public final class SpelCompiler implements Opcodes {
 	 */
 	@SuppressWarnings("unchecked")
 	private Class<? extends CompiledExpression> loadClass(String name, byte[] bytes) {
-		if (this.ccl.getClassesDefinedCount() > CLASSES_DEFINED_LIMIT) {
-			this.ccl = new ChildClassLoader(this.ccl.getParent());
+		ChildClassLoader ccl = this.childClassLoader;
+		if (ccl.getClassesDefinedCount() >= CLASSES_DEFINED_LIMIT) {
+			synchronized (this) {
+				ChildClassLoader currentCcl = this.childClassLoader;
+				if (ccl == currentCcl) {
+					// Still the same ClassLoader that needs to be replaced...
+					ccl = new ChildClassLoader(ccl.getParent());
+					this.childClassLoader = ccl;
+				}
+				else {
+					// Already replaced by some other thread, let's pick it up.
+					ccl = currentCcl;
+				}
+			}
 		}
-		return (Class<? extends CompiledExpression>) this.ccl.defineClass(name, bytes);
+		return (Class<? extends CompiledExpression>) ccl.defineClass(name, bytes);
 	}

+
 	/**
 	 * Factory method for compiler instances. The returned SpelCompiler will
 	 * attach a class loader as the child of the given class loader and this
@@ -211,21 +226,28 @@ public final class SpelCompiler implements Opcodes {
 	 */
 	public static SpelCompiler getCompiler(@Nullable ClassLoader classLoader) {
 		ClassLoader clToUse = (classLoader != null ? classLoader : ClassUtils.getDefaultClassLoader());
-		synchronized (compilers) {
-			SpelCompiler compiler = compilers.get(clToUse);
-			if (compiler == null) {
-				compiler = new SpelCompiler(clToUse);
-				compilers.put(clToUse, compiler);
+		// Quick check for existing compiler without lock contention
+		SpelCompiler compiler = compilers.get(clToUse);
+		if (compiler == null) {
+			// Full lock now since we're creating a child ClassLoader
+			synchronized (compilers) {
+				compiler = compilers.get(clToUse);
+				if (compiler == null) {
+					compiler = new SpelCompiler(clToUse);
+					compilers.put(clToUse, compiler);
+				}
 			}
-			return compiler;
 		}
+		return compiler;
 	}

 	/**
-	 * Request that an attempt is made to compile the specified expression. It may fail if
-	 * components of the expression are not suitable for compilation or the data types
-	 * involved are not suitable for compilation. Used for testing.
-	 * @return true if the expression was successfully compiled
+	 * Request that an attempt is made to compile the specified expression.
+	 * It may fail if components of the expression are not suitable for compilation
+	 * or the data types involved are not suitable for compilation. Used for testing.
+	 * @param expression the expression to compile
+	 * @return {@code true} if the expression was successfully compiled,
+	 * {@code false} otherwise
 	 */
 	public static boolean compile(Expression expression) {
 		return (expression instanceof SpelExpression && ((SpelExpression) expression).compileExpression());
@@ -250,24 +272,27 @@ public final class SpelCompiler implements Opcodes {

 		private static final URL[] NO_URLS = new URL[0];

-		private int classesDefinedCount = 0;
+		private final AtomicInteger classesDefinedCount = new AtomicInteger(0);

 		public ChildClassLoader(@Nullable ClassLoader classLoader) {
 			super(NO_URLS, classLoader);
 		}

-		int getClassesDefinedCount() {
-			return this.classesDefinedCount;
-		}
-
 		public Class<?> defineClass(String name, byte[] bytes) {
 			Class<?> clazz = super.defineClass(name, bytes, 0, bytes.length);
-			this.classesDefinedCount++;
+			this.classesDefinedCount.incrementAndGet();
 			return clazz;
 		}
+
+		public int getClassesDefinedCount() {
+			return this.classesDefinedCount.get();
+		}
 	}


+	/**
+	 * An ASM ClassWriter extension bound to the SpelCompiler's ClassLoader.
+	 */
 	private class ExpressionClassWriter extends ClassWriter {

 		public ExpressionClassWriter() {
@@ -276,7 +301,7 @@ public final class SpelCompiler implements Opcodes {

 		@Override
 		protected ClassLoader getClassLoader() {
-			return ccl;
+			return childClassLoader;
 		}
 	}

@@ -395,6 +395,11 @@ public class ReflectivePropertyAccessor implements PropertyAccessor {
 		if (method == null) {
 			method = findMethodForProperty(getPropertyMethodSuffixes(propertyName),
 					"is", clazz, mustBeStatic, 0, BOOLEAN_TYPES);
+			if (method == null) {
+				// Record-style plain accessor method, e.g. name()
+				method = findMethodForProperty(new String[] {propertyName},
+						"", clazz, mustBeStatic, 0, ANY_TYPES);
+			}
 		}
 		return method;
 	}
@@ -683,12 +688,11 @@ public class ReflectivePropertyAccessor implements PropertyAccessor {
 					return true;
 				}
 				getterName = "is" + StringUtils.capitalize(name);
-				return getterName.equals(method.getName());
-			}
-			else {
-				Field field = (Field) this.member;
-				return field.getName().equals(name);
+				if (getterName.equals(method.getName())) {
+					return true;
+				}
 			}
+			return this.member.getName().equals(name);
 		}

 		@Override
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -36,6 +36,7 @@ import org.springframework.expression.spel.support.SimpleEvaluationContext;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
 import org.springframework.expression.spel.testresources.Inventor;
 import org.springframework.expression.spel.testresources.Person;
+import org.springframework.expression.spel.testresources.RecordPerson;

 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
@@ -191,6 +192,20 @@ public class PropertyAccessTests extends AbstractExpressionTests {
 				parser.parseExpression("name='p3'").getValue(context, target));
 	}

+	@Test
+	public void propertyReadOnlyWithRecordStyle() {
+		EvaluationContext context = SimpleEvaluationContext.forReadOnlyDataBinding().build();
+
+		Expression expr = parser.parseExpression("name");
+		RecordPerson target1 = new RecordPerson("p1");
+		assertThat(expr.getValue(context, target1)).isEqualTo("p1");
+		RecordPerson target2 = new RecordPerson("p2");
+		assertThat(expr.getValue(context, target2)).isEqualTo("p2");
+
+		assertThatExceptionOfType(SpelEvaluationException.class).isThrownBy(() ->
+				parser.parseExpression("name='p3'").getValue(context, target2));
+	}
+
 	@Test
 	public void propertyReadWrite() {
 		EvaluationContext context = SimpleEvaluationContext.forReadWriteDataBinding().build();
@@ -4180,6 +4180,13 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 		assertThat(expression.getValue(tc)).isEqualTo("value4");
 		assertCanCompile(expression);
 		assertThat(expression.getValue(tc)).isEqualTo("value4");
+
+		// record-style accessor
+		expression = parser.parseExpression("strawberry");
+		assertCantCompile(expression);
+		assertThat(expression.getValue(tc)).isEqualTo("value5");
+		assertCanCompile(expression);
+		assertThat(expression.getValue(tc)).isEqualTo("value5");
 	}

 	@Test
@@ -4553,23 +4560,9 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 		Object v = expression.getValue(ctx,holder);
 		assertThat(v).isEqualTo("abc");

-		//	// time it interpreted
-		//	long stime = System.currentTimeMillis();
-		//	for (int i = 0; i < 100000; i++) {
-		//		v = expression.getValue(ctx,holder);
-		//	}
-		//	System.out.println((System.currentTimeMillis() - stime));
-
 		assertCanCompile(expression);
 		v = expression.getValue(ctx,holder);
 		assertThat(v).isEqualTo("abc");
-
-		//	// time it compiled
-		//	stime = System.currentTimeMillis();
-		//	for (int i = 0; i < 100000; i++) {
-		//		v = expression.getValue(ctx,holder);
-		//	}
-		//	System.out.println((System.currentTimeMillis() - stime));
 	}

 	@Test
@@ -4985,13 +4978,12 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 		assertThat(fast.compileExpression()).isTrue();
 		r.setValue2(null);
 		// try the numbers 0,1,2,null
-		for (int i=0;i<4;i++) {
-			r.setValue(i<3?i:null);
+		for (int i = 0; i < 4; i++) {
+			r.setValue(i < 3 ? i : null);
 			boolean slowResult = (Boolean)slow.getValue(ctx);
 			boolean fastResult = (Boolean)fast.getValue(ctx);
-			// System.out.println("Trying "+expressionText+" with value="+r.getValue()+" result is "+slowResult);
-			assertThat(fastResult).as(" Differing results: expression="+expressionText+
-						" value="+r.getValue()+" slow="+slowResult+" fast="+fastResult).isEqualTo(slowResult);
+			assertThat(fastResult).as("Differing results: expression=" + expressionText +
+						" value=" + r.getValue() + " slow=" + slowResult + " fast="+fastResult).isEqualTo(slowResult);
 		}
 	}

@@ -5002,13 +4994,12 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 		assertThat(fast.compileExpression()).isTrue();
 		Reg r = (Reg)ctx.getRootObject().getValue();
 		// try the numbers 0,1,2,null
-		for (int i=0;i<4;i++) {
-			r.setValue(i<3?i:null);
+		for (int i = 0; i < 4; i++) {
+			r.setValue(i < 3 ? i : null);
 			boolean slowResult = (Boolean)slow.getValue(ctx);
 			boolean fastResult = (Boolean)fast.getValue(ctx);
-			// System.out.println("Trying "+expressionText+" with value="+r.getValue()+" result is "+slowResult);
-			assertThat(fastResult).as(" Differing results: expression="+expressionText+
-						" value="+r.getValue()+" slow="+slowResult+" fast="+fastResult).isEqualTo(slowResult);
+			assertThat(fastResult).as("Differing results: expression=" + expressionText +
+					" value=" + r.getValue() + " slow=" + slowResult + " fast="+fastResult).isEqualTo(slowResult);
 		}
 	}

@@ -5839,7 +5830,6 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {

 		public String orange = "value1";
 		public static String apple = "value2";
-
 		public long peach = 34L;

 		public String getBanana() {
@@ -5849,6 +5839,10 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 		public static String getPlum() {
 			return "value4";
 		}
+
+		public String strawberry() {
+			return "value5";
+		}
 	}


@@ -76,7 +76,6 @@ import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 */
 public class SpelReproTests extends AbstractExpressionTests {

-
 	@Test
 	public void NPE_SPR5661() {
 		evaluate("joinThreeStrings('a',null,'c')", "anullc", String.class);
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -89,8 +89,8 @@ public class ReflectionHelperTests extends AbstractExpressionTests {
 		assertThat(tv1).isNotEqualTo(tv3);
 		assertThat(tv2).isNotEqualTo(tv3);
 		assertThat(tv2.hashCode()).isEqualTo(tv1.hashCode());
-		assertThat(tv3.hashCode()).isNotEqualTo((long) tv1.hashCode());
-		assertThat(tv3.hashCode()).isNotEqualTo((long) tv2.hashCode());
+		assertThat(tv3.hashCode()).isNotEqualTo(tv1.hashCode());
+		assertThat(tv3.hashCode()).isNotEqualTo(tv2.hashCode());
 	}

 	@Test
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -16,9 +16,10 @@

 package org.springframework.expression.spel.testresources;

-///CLOVER:OFF
 public class Person {
+
 	private String privateName;
+
 	Company company;

 	public Person(String name) {
@@ -41,4 +42,5 @@ public class Person {
 	public Company getCompany() {
 		return company;
 	}
+
 }
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.expression.spel.testresources;
+
+public class RecordPerson {
+
+	private String name;
+
+	private Company company;
+
+	public RecordPerson(String name) {
+		this.name = name;
+	}
+
+	public RecordPerson(String name, Company company) {
+		this.name = name;
+		this.company = company;
+	}
+
+	public String name() {
+		return name;
+	}
+
+	public Company company() {
+		return company;
+	}
+
+}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -19,19 +19,25 @@ package org.springframework.expression.spel.testresources;
 import java.util.List;

 public class TestAddress{
-		private String street;
-		private List<String> crossStreets;

-		public String getStreet() {
-			return street;
-		}
-		public void setStreet(String street) {
-			this.street = street;
-		}
-		public List<String> getCrossStreets() {
-			return crossStreets;
-		}
-		public void setCrossStreets(List<String> crossStreets) {
-			this.crossStreets = crossStreets;
-		}
+	private String street;
+
+	private List<String> crossStreets;
+
+	public String getStreet() {
+		return street;
 	}
+
+	public void setStreet(String street) {
+		this.street = street;
+	}
+
+	public List<String> getCrossStreets() {
+		return crossStreets;
+	}
+
+	public void setCrossStreets(List<String> crossStreets) {
+		this.crossStreets = crossStreets;
+	}
+
+}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -17,19 +17,25 @@
 package org.springframework.expression.spel.testresources;

 public class TestPerson {
-		private String name;
-		private TestAddress address;

-		public String getName() {
-			return name;
-		}
-		public void setName(String name) {
-			this.name = name;
-		}
-		public TestAddress getAddress() {
-			return address;
-		}
-		public void setAddress(TestAddress address) {
-			this.address = address;
-		}
+	private String name;
+
+	private TestAddress address;
+
+	public String getName() {
+		return name;
 	}
+
+	public void setName(String name) {
+		this.name = name;
+	}
+
+	public TestAddress getAddress() {
+		return address;
+	}
+
+	public void setAddress(TestAddress address) {
+		this.address = address;
+	}
+
+}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2012 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -36,7 +36,7 @@ public interface SqlProvider {
 	/**
 	 * Return the SQL string for this object, i.e.
 	 * typically the SQL used for creating statements.
-	 * @return the SQL string, or {@code null}
+	 * @return the SQL string, or {@code null} if not available
 	 */
 	@Nullable
 	String getSql();
@@ -637,21 +637,23 @@ public class CallMetaDataContext {
 			schemaNameToUse = this.metaDataProvider.schemaNameToUse(getSchemaName());
 		}

-		String procedureNameToUse = this.metaDataProvider.procedureNameToUse(getProcedureName());
 		if (isFunction() || isReturnValueRequired()) {
-			callString = new StringBuilder().append("{? = call ").
-					append(StringUtils.hasLength(catalogNameToUse) ? catalogNameToUse + "." : "").
-					append(StringUtils.hasLength(schemaNameToUse) ? schemaNameToUse + "." : "").
-					append(procedureNameToUse).append("(");
+			callString = new StringBuilder("{? = call ");
 			parameterCount = -1;
 		}
 		else {
-			callString = new StringBuilder().append("{call ").
-					append(StringUtils.hasLength(catalogNameToUse) ? catalogNameToUse + "." : "").
-					append(StringUtils.hasLength(schemaNameToUse) ? schemaNameToUse + "." : "").
-					append(procedureNameToUse).append("(");
+			callString = new StringBuilder("{call ");
 		}

+		if (StringUtils.hasLength(catalogNameToUse)) {
+			callString.append(catalogNameToUse).append(".");
+		}
+		if (StringUtils.hasLength(schemaNameToUse)) {
+			callString.append(schemaNameToUse).append(".");
+		}
+		callString.append(this.metaDataProvider.procedureNameToUse(getProcedureName()));
+		callString.append("(");
+
 		for (SqlParameter parameter : this.callParameters) {
 			if (!parameter.isResultsParameter()) {
 				if (parameterCount > 0) {
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -83,7 +83,7 @@ public abstract class NamedParameterUtils {
 		Assert.notNull(sql, "SQL must not be null");

 		Set<String> namedParameters = new HashSet<>();
-		String sqlToUse = sql;
+		StringBuilder sqlToUse = new StringBuilder(sql);
 		List<ParameterHolder> parameterList = new ArrayList<>();

 		char[] statement = sql.toCharArray();
@@ -155,7 +155,7 @@ public abstract class NamedParameterUtils {
 					int j = i + 1;
 					if (j < statement.length && statement[j] == ':') {
 						// escaped ":" should be skipped
-						sqlToUse = sqlToUse.substring(0, i - escapes) + sqlToUse.substring(i - escapes + 1);
+						sqlToUse.deleteCharAt(i - escapes);
 						escapes++;
 						i = i + 2;
 						continue;
@@ -174,7 +174,7 @@ public abstract class NamedParameterUtils {
 			}
 			i++;
 		}
-		ParsedSql parsedSql = new ParsedSql(sqlToUse);
+		ParsedSql parsedSql = new ParsedSql(sqlToUse.toString());
 		for (ParameterHolder ph : parameterList) {
 			parsedSql.addNamedParameter(ph.getParameterName(), ph.getStartIndex(), ph.getEndIndex());
 		}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -28,11 +28,11 @@ import java.util.List;
 */
 public class ParsedSql {

-	private String originalSql;
+	private final String originalSql;

-	private List<String> parameterNames = new ArrayList<>();
+	private final List<String> parameterNames = new ArrayList<>();

-	private List<int[]> parameterIndexes = new ArrayList<>();
+	private final List<int[]> parameterIndexes = new ArrayList<>();

 	private int namedParameterCount;

@@ -1,6 +1,7 @@
 description = "Spring Messaging"

 apply plugin: "kotlin"
+apply plugin: "kotlinx-serialization"

 dependencies {
 	compile(project(":spring-beans"))
@@ -17,6 +18,7 @@ dependencies {
 	optional("javax.xml.bind:jaxb-api")
 	optional("com.google.protobuf:protobuf-java-util")
 	optional("org.jetbrains.kotlinx:kotlinx-coroutines-reactor")
+	optional("org.jetbrains.kotlinx:kotlinx-serialization-json")
 	testCompile(project(":kotlin-coroutines"))
 	testCompile(testFixtures(project(":spring-core")))
 	testCompile("javax.inject:javax.inject-tck")
@@ -0,0 +1,109 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.messaging.converter;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.io.Writer;
+import java.lang.reflect.Type;
+import java.util.Map;
+
+import kotlinx.serialization.KSerializer;
+import kotlinx.serialization.SerializersKt;
+import kotlinx.serialization.json.Json;
+
+import org.springframework.util.ConcurrentReferenceHashMap;
+import org.springframework.util.FileCopyUtils;
+
+/**
+ * Implementation of {@link MessageConverter} that can read and write JSON
+ * using <a href="https://github.com/Kotlin/kotlinx.serialization">kotlinx.serialization</a>.
+ *
+ * <p>This converter can be used to bind {@code @Serializable} Kotlin classes.
+ *
+ * @author Sebastien Deleuze
+ * @since 5.3
+ */
+public class KotlinSerializationJsonMessageConverter extends AbstractJsonMessageConverter {
+
+	private static final Map<Type, KSerializer<Object>> serializerCache = new ConcurrentReferenceHashMap<>();
+
+	private final Json json;
+
+
+	/**
+	 * Construct a new {@code KotlinSerializationJsonMessageConverter} with default configuration.
+	 */
+	public KotlinSerializationJsonMessageConverter() {
+		this(Json.Default);
+	}
+
+	/**
+	 * Construct a new {@code KotlinSerializationJsonMessageConverter} with the given delegate.
+	 * @param json the Json instance to use
+	 */
+	public KotlinSerializationJsonMessageConverter(Json json) {
+		this.json = json;
+	}
+
+	@Override
+	protected Object fromJson(Reader reader, Type resolvedType) {
+		try {
+			return fromJson(FileCopyUtils.copyToString(reader), resolvedType);
+		}
+		catch (IOException ex) {
+			throw new MessageConversionException("Could not read JSON: " + ex.getMessage(), ex);
+		}
+	}
+
+	@Override
+	protected Object fromJson(String payload, Type resolvedType) {
+		return this.json.decodeFromString(serializer(resolvedType), payload);
+	}
+
+	@Override
+	protected void toJson(Object payload, Type resolvedType, Writer writer) {
+		try {
+			writer.write(toJson(payload, resolvedType).toCharArray());
+		}
+		catch (IOException ex) {
+			throw new MessageConversionException("Could not write JSON: " + ex.getMessage(), ex);
+		}
+	}
+
+	@Override
+	protected String toJson(Object payload, Type resolvedType) {
+		return this.json.encodeToString(serializer(resolvedType), payload);
+	}
+
+	/**
+	 * Tries to find a serializer that can marshall or unmarshall instances of the given type
+	 * using kotlinx.serialization. If no serializer can be found, an exception is thrown.
+	 * <p>Resolved serializers are cached and cached results are returned on successive calls.
+	 * @param type the type to find a serializer for
+	 * @return a resolved serializer for the given type
+	 * @throws RuntimeException if no serializer supporting the given type can be found
+	 */
+	private KSerializer<Object> serializer(Type type) {
+		KSerializer<Object> serializer = serializerCache.get(type);
+		if (serializer == null) {
+			serializer = SerializersKt.serializer(type);
+			serializerCache.put(type, serializer);
+		}
+		return serializer;
+	}
+}
@@ -247,14 +247,15 @@ public class MappingJackson2MessageConverter extends AbstractMessageConverter {
 			if (byte[].class == getSerializedPayloadClass()) {
 				ByteArrayOutputStream out = new ByteArrayOutputStream(1024);
 				JsonEncoding encoding = getJsonEncoding(getMimeType(headers));
-				JsonGenerator generator = this.objectMapper.getFactory().createGenerator(out, encoding);
-				if (view != null) {
-					this.objectMapper.writerWithView(view).writeValue(generator, payload);
+				try (JsonGenerator generator = this.objectMapper.getFactory().createGenerator(out, encoding)) {
+					if (view != null) {
+						this.objectMapper.writerWithView(view).writeValue(generator, payload);
+					}
+					else {
+						this.objectMapper.writeValue(generator, payload);
+					}
+					payload = out.toByteArray();
 				}
-				else {
-					this.objectMapper.writeValue(generator, payload);
-				}
-				payload = out.toByteArray();
 			}
 			else {
 				// Assuming a text-based target payload
@@ -21,8 +21,6 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Map;

-import kotlin.reflect.KFunction;
-import kotlin.reflect.jvm.ReflectJvmMapping;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.reactivestreams.Publisher;
@@ -123,7 +121,6 @@ public abstract class AbstractEncoderMethodReturnValueHandler implements Handler
 				handleEncodedContent(Flux.from(publisher), returnType, message));
 	}

-	@SuppressWarnings("unchecked")
 	private Flux<DataBuffer> encodeContent(
 			@Nullable Object content, MethodParameter returnType, DataBufferFactory bufferFactory,
 			@Nullable MimeType mimeType, Map<String, Object> hints) {
@@ -135,11 +132,10 @@ public abstract class AbstractEncoderMethodReturnValueHandler implements Handler
 		ResolvableType elementType;
 		if (adapter != null) {
 			publisher = adapter.toPublisher(content);
-			boolean isUnwrapped = KotlinDetector.isKotlinReflectPresent() &&
-					KotlinDetector.isKotlinType(returnType.getContainingClass()) &&
-					KotlinDelegate.isSuspend(returnType.getMethod()) &&
-					!COROUTINES_FLOW_CLASS_NAME.equals(returnValueType.toClass().getName());
-			ResolvableType genericType = isUnwrapped ? returnValueType : returnValueType.getGeneric();
+			Method method = returnType.getMethod();
+			boolean isUnwrapped = (method != null && KotlinDetector.isSuspendingFunction(method) &&
+					!COROUTINES_FLOW_CLASS_NAME.equals(returnValueType.toClass().getName()));
+			ResolvableType genericType = (isUnwrapped ? returnValueType : returnValueType.getGeneric());
 			elementType = getElementType(adapter, genericType);
 		}
 		else {
@@ -218,19 +214,4 @@ public abstract class AbstractEncoderMethodReturnValueHandler implements Handler
 	 */
 	protected abstract Mono<Void> handleNoContent(MethodParameter returnType, Message<?> message);

-
-	/**
-	 * Inner class to avoid a hard dependency on Kotlin at runtime.
-	 */
-	private static class KotlinDelegate {
-
-		private static boolean isSuspend(@Nullable Method method) {
-			if (method == null) {
-				return false;
-			}
-			KFunction<?> function = ReflectJvmMapping.getKotlinFunction(method);
-			return (function != null && function.isSuspend());
-		}
-	}
-
 }
@@ -177,8 +177,7 @@ class MessagingRSocket implements RSocket {
 					}
 				})
 				.thenMany(Flux.defer(() -> responseRef.get() != null ?
-						responseRef.get() :
-						Mono.error(new IllegalStateException("Something went wrong: reply Mono not set"))));
+						responseRef.get() : Mono.error(new IllegalStateException("Expected response"))));
 	}

 	private DataBuffer retainDataAndReleasePayload(Payload payload) {
@@ -125,6 +125,12 @@ public abstract class AbstractBrokerMessageHandler
 		return this.brokerChannel;
 	}

+	/**
+	 * Return destination prefixes prefixes to use to filter messages to forward
+	 * to the broker. Messages that have a destination and where the destination
+	 * doesn't match are ignored.
+	 * <p>By default this is not set.
+	 */
 	public Collection<String> getDestinationPrefixes() {
 		return this.destinationPrefixes;
 	}
@@ -36,6 +36,7 @@ import org.springframework.messaging.converter.CompositeMessageConverter;
 import org.springframework.messaging.converter.DefaultContentTypeResolver;
 import org.springframework.messaging.converter.GsonMessageConverter;
 import org.springframework.messaging.converter.JsonbMessageConverter;
+import org.springframework.messaging.converter.KotlinSerializationJsonMessageConverter;
 import org.springframework.messaging.converter.MappingJackson2MessageConverter;
 import org.springframework.messaging.converter.MessageConverter;
 import org.springframework.messaging.converter.StringMessageConverter;
@@ -101,6 +102,8 @@ public abstract class AbstractMessageBrokerConfiguration implements ApplicationC

 	private static final boolean jsonbPresent;

+	private static final boolean kotlinSerializationJsonPresent;
+

 	static {
 		ClassLoader classLoader = AbstractMessageBrokerConfiguration.class.getClassLoader();
@@ -108,6 +111,7 @@ public abstract class AbstractMessageBrokerConfiguration implements ApplicationC
 				ClassUtils.isPresent("com.fasterxml.jackson.core.JsonGenerator", classLoader);
 		gsonPresent = ClassUtils.isPresent("com.google.gson.Gson", classLoader);
 		jsonbPresent = ClassUtils.isPresent("javax.json.bind.Jsonb", classLoader);
+		kotlinSerializationJsonPresent = ClassUtils.isPresent("kotlinx.serialization.json.Json", classLoader);
 	}


@@ -411,6 +415,9 @@ public abstract class AbstractMessageBrokerConfiguration implements ApplicationC
 			else if (jsonbPresent) {
 				converters.add(new JsonbMessageConverter());
 			}
+			else if (kotlinSerializationJsonPresent) {
+				converters.add(new KotlinSerializationJsonMessageConverter());
+			}
 		}
 		return new CompositeMessageConverter(converters);
 	}
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2018 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -21,6 +21,7 @@ import org.springframework.messaging.MessageChannel;
 import org.springframework.messaging.SubscribableChannel;
 import org.springframework.messaging.simp.stomp.StompBrokerRelayMessageHandler;
 import org.springframework.messaging.tcp.TcpOperations;
+import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;

 /**
@@ -55,6 +56,9 @@ public class StompBrokerRelayRegistration extends AbstractBrokerRegistration {
 	@Nullable
 	private TcpOperations<byte[]> tcpClient;

+	@Nullable
+	private TaskScheduler taskScheduler;
+
 	private boolean autoStartup = true;

 	@Nullable
@@ -178,8 +182,27 @@ public class StompBrokerRelayRegistration extends AbstractBrokerRegistration {
 	 * specified are effectively ignored.
 	 * @since 4.3.15
 	 */
-	public void setTcpClient(TcpOperations<byte[]> tcpClient) {
+	public StompBrokerRelayRegistration setTcpClient(TcpOperations<byte[]> tcpClient) {
 		this.tcpClient = tcpClient;
+		return this;
+	}
+
+	/**
+	 * Some STOMP clients (e.g. stomp-js) always send heartbeats at a fixed rate
+	 * but others (Spring STOMP client) do so only when no other messages are
+	 * sent. However messages with a non-broker {@link #getDestinationPrefixes()
+	 * destination prefix} aren't forwarded and as a result the broker may deem
+	 * the connection inactive.
+	 * <p>When this {@link TaskScheduler} is set, it is used to reset a count of
+	 * the number of messages sent from client to broker since the beginning of
+	 * the current heartbeat period. This is then used to decide whether to send
+	 * a heartbeat to the broker when ignoring a message with a non-broker
+	 * destination prefix.
+	 * @since 5.3
+	 */
+	public StompBrokerRelayRegistration setTaskScheduler(@Nullable TaskScheduler taskScheduler) {
+		this.taskScheduler = taskScheduler;
+		return this;
 	}

 	/**
@@ -233,7 +256,6 @@ public class StompBrokerRelayRegistration extends AbstractBrokerRegistration {

 	@Override
 	protected StompBrokerRelayMessageHandler getMessageHandler(SubscribableChannel brokerChannel) {
-
 		StompBrokerRelayMessageHandler handler = new StompBrokerRelayMessageHandler(
 				getClientInboundChannel(), getClientOutboundChannel(),
 				brokerChannel, getDestinationPrefixes());
@@ -259,6 +281,9 @@ public class StompBrokerRelayRegistration extends AbstractBrokerRegistration {
 		if (this.tcpClient != null) {
 			handler.setTcpClient(this.tcpClient);
 		}
+		if (this.taskScheduler != null) {
+			handler.setTaskScheduler(this.taskScheduler);
+		}

 		handler.setAutoStartup(this.autoStartup);

@@ -16,7 +16,6 @@

 package org.springframework.messaging.simp.stomp;

-import org.springframework.messaging.tcp.TcpConnectionHandler;
 import org.springframework.util.concurrent.ListenableFuture;

 /**
@@ -30,7 +29,7 @@ import org.springframework.util.concurrent.ListenableFuture;
 * @author Rossen Stoyanchev
 * @since 4.2
 */
-public interface ConnectionHandlingStompSession extends StompSession, TcpConnectionHandler<byte[]> {
+public interface ConnectionHandlingStompSession extends StompSession, StompTcpConnectionHandler<byte[]> {

 	/**
 	 * Return a future that will complete when the session is ready for use.
@@ -45,6 +45,7 @@ import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.AlternativeJdkIdGenerator;
 import org.springframework.util.Assert;
 import org.springframework.util.IdGenerator;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.util.concurrent.ListenableFuture;
 import org.springframework.util.concurrent.ListenableFutureCallback;
@@ -133,6 +134,13 @@ public class DefaultStompSession implements ConnectionHandlingStompSession {
 		return this.sessionId;
 	}

+	@Override
+	public StompHeaderAccessor getConnectHeaders() {
+		StompHeaderAccessor accessor = createHeaderAccessor(StompCommand.CONNECT);
+		accessor.addNativeHeaders(this.connectHeaders);
+		return accessor;
+	}
+
 	/**
 	 * Return the configured session handler.
 	 */
@@ -256,7 +264,7 @@ public class DefaultStompSession implements ConnectionHandlingStompSession {
 	private Message<byte[]> createMessage(StompHeaderAccessor accessor, @Nullable Object payload) {
 		accessor.updateSimpMessageHeadersFromStompHeaders();
 		Message<byte[]> message;
-		if (StringUtils.isEmpty(payload) || (payload instanceof byte[] && ((byte[]) payload).length == 0)) {
+		if (ObjectUtils.isEmpty(payload)) {
 			message = MessageBuilder.createMessage(EMPTY_PAYLOAD, accessor.getMessageHeaders());
 		}
 		else {
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -41,10 +41,10 @@ import org.springframework.messaging.support.MessageHeaderAccessor;
 import org.springframework.messaging.support.MessageHeaderInitializer;
 import org.springframework.messaging.tcp.FixedIntervalReconnectStrategy;
 import org.springframework.messaging.tcp.TcpConnection;
-import org.springframework.messaging.tcp.TcpConnectionHandler;
 import org.springframework.messaging.tcp.TcpOperations;
 import org.springframework.messaging.tcp.reactor.ReactorNettyCodec;
 import org.springframework.messaging.tcp.reactor.ReactorNettyTcpClient;
+import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.Assert;
 import org.springframework.util.concurrent.ListenableFuture;
 import org.springframework.util.concurrent.ListenableFutureCallback;
@@ -99,13 +99,15 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler

 	private static final ListenableFutureTask<Void> EMPTY_TASK = new ListenableFutureTask<>(new VoidCallable());

-	private static final Message<byte[]> HEARTBEAT_MESSAGE;
+	private static final StompHeaderAccessor HEART_BEAT_ACCESSOR;

+	private static final Message<byte[]> HEARTBEAT_MESSAGE;

 	static {
 		EMPTY_TASK.run();
-		StompHeaderAccessor accessor = StompHeaderAccessor.createForHeartbeat();
-		HEARTBEAT_MESSAGE = MessageBuilder.createMessage(StompDecoder.HEARTBEAT_PAYLOAD, accessor.getMessageHeaders());
+		HEART_BEAT_ACCESSOR = StompHeaderAccessor.createForHeartbeat();
+		HEARTBEAT_MESSAGE = MessageBuilder.createMessage(
+				StompDecoder.HEARTBEAT_PAYLOAD, HEART_BEAT_ACCESSOR.getMessageHeaders());
 	}


@@ -138,7 +140,10 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler

 	private final DefaultStats stats = new DefaultStats();

-	private final Map<String, StompConnectionHandler> connectionHandlers = new ConcurrentHashMap<>();
+	private final Map<String, RelayConnectionHandler> connectionHandlers = new ConcurrentHashMap<>();
+
+	@Nullable
+	private TaskScheduler taskScheduler;


 	/**
@@ -404,6 +409,22 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 		return this.connectionHandlers.size();
 	}

+	/**
+	 * Configure the {@link TaskScheduler} to use to reset client-to-broker
+	 * message count in the current heartbeat period. For more details, see
+	 * {@link org.springframework.messaging.simp.config.StompBrokerRelayRegistration#setTaskScheduler(TaskScheduler)}.
+	 * @param taskScheduler the scheduler to use
+	 * @since 5.3
+	 */
+	public void setTaskScheduler(@Nullable TaskScheduler taskScheduler) {
+		this.taskScheduler = taskScheduler;
+	}
+
+	@Nullable
+	public TaskScheduler getTaskScheduler() {
+		return this.taskScheduler;
+	}
+

 	@Override
 	protected void startInternal() {
@@ -429,11 +450,15 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 			logger.debug("Forwarding " + accessor.getShortLogMessage(EMPTY_PAYLOAD));
 		}

-		SystemStompConnectionHandler handler = new SystemStompConnectionHandler(accessor);
+		SystemSessionConnectionHandler handler = new SystemSessionConnectionHandler(accessor);
 		this.connectionHandlers.put(handler.getSessionId(), handler);

 		this.stats.incrementConnectCount();
 		this.tcpClient.connect(handler, new FixedIntervalReconnectStrategy(5000));
+
+		if (this.taskScheduler != null) {
+			this.taskScheduler.scheduleWithFixedDelay(new ClientSendMessageCountTask(), 5000);
+		}
 	}

 	private ReactorNettyTcpClient<byte[]> initTcpClient() {
@@ -469,7 +494,7 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 				throw new MessageDeliveryException("Message broker not active. Consider subscribing to " +
 						"receive BrokerAvailabilityEvent's from an ApplicationListener Spring bean.");
 			}
-			StompConnectionHandler handler = this.connectionHandlers.get(sessionId);
+			RelayConnectionHandler handler = this.connectionHandlers.get(sessionId);
 			if (handler != null) {
 				handler.sendStompErrorFrameToClient("Broker not available.");
 				handler.clearConnection();
@@ -526,11 +551,6 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 			stompAccessor.setSessionId(sessionId);
 		}

-		String destination = stompAccessor.getDestination();
-		if (command != null && command.requiresDestination() && !checkDestinationPrefix(destination)) {
-			return;
-		}
-
 		if (StompCommand.CONNECT.equals(command) || StompCommand.STOMP.equals(command)) {
 			if (logger.isDebugEnabled()) {
 				logger.debug(stompAccessor.getShortLogMessage(EMPTY_PAYLOAD));
@@ -541,14 +561,14 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 			if (getVirtualHost() != null) {
 				stompAccessor.setHost(getVirtualHost());
 			}
-			StompConnectionHandler handler = new StompConnectionHandler(sessionId, stompAccessor);
+			RelayConnectionHandler handler = new RelayConnectionHandler(sessionId, stompAccessor);
 			this.connectionHandlers.put(sessionId, handler);
 			this.stats.incrementConnectCount();
 			Assert.state(this.tcpClient != null, "No TCP client available");
 			this.tcpClient.connect(handler);
 		}
 		else if (StompCommand.DISCONNECT.equals(command)) {
-			StompConnectionHandler handler = this.connectionHandlers.get(sessionId);
+			RelayConnectionHandler handler = this.connectionHandlers.get(sessionId);
 			if (handler == null) {
 				if (logger.isDebugEnabled()) {
 					logger.debug("Ignoring DISCONNECT in session " + sessionId + ". Connection already cleaned up.");
@@ -559,13 +579,23 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 			handler.forward(message, stompAccessor);
 		}
 		else {
-			StompConnectionHandler handler = this.connectionHandlers.get(sessionId);
+			RelayConnectionHandler handler = this.connectionHandlers.get(sessionId);
 			if (handler == null) {
 				if (logger.isDebugEnabled()) {
 					logger.debug("No TCP connection for session " + sessionId + " in " + message);
 				}
 				return;
 			}
+
+			String destination = stompAccessor.getDestination();
+			if (command != null && command.requiresDestination() && !checkDestinationPrefix(destination)) {
+				// Not a broker destination but send a heartbeat to keep the connection
+				if (handler.shouldSendHeartbeatForIgnoredMessage()) {
+					handler.forward(HEARTBEAT_MESSAGE, HEART_BEAT_ACCESSOR);
+				}
+				return;
+			}
+
 			handler.forward(message, stompAccessor);
 		}
 	}
@@ -580,14 +610,14 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 	}


-	private class StompConnectionHandler implements TcpConnectionHandler<byte[]> {
+	private class RelayConnectionHandler implements StompTcpConnectionHandler<byte[]> {

 		private final String sessionId;

-		private final boolean isRemoteClientSession;
-
 		private final StompHeaderAccessor connectHeaders;

+		private final boolean isRemoteClientSession;
+
 		private final MessageChannel outboundChannel;

 		@Nullable
@@ -595,24 +625,47 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler

 		private volatile boolean isStompConnected;

+		private long clientSendInterval;

-		protected StompConnectionHandler(String sessionId, StompHeaderAccessor connectHeaders) {
+		@Nullable
+		private final AtomicInteger clientSendMessageCount;
+
+		private long clientSendMessageTimestamp;
+
+
+		protected RelayConnectionHandler(String sessionId, StompHeaderAccessor connectHeaders) {
 			this(sessionId, connectHeaders, true);
 		}

-		private StompConnectionHandler(String sessionId, StompHeaderAccessor connectHeaders, boolean isClientSession) {
+		private RelayConnectionHandler(String sessionId, StompHeaderAccessor connectHeaders, boolean isClientSession) {
 			Assert.notNull(sessionId, "'sessionId' must not be null");
 			Assert.notNull(connectHeaders, "'connectHeaders' must not be null");
 			this.sessionId = sessionId;
 			this.connectHeaders = connectHeaders;
 			this.isRemoteClientSession = isClientSession;
 			this.outboundChannel = getClientOutboundChannelForSession(sessionId);
+			if (isClientSession && taskScheduler != null) {
+				this.clientSendInterval = connectHeaders.getHeartbeat()[0];
+			}
+			if (this.clientSendInterval > 0) {
+				this.clientSendMessageCount = new AtomicInteger();
+				this.clientSendMessageTimestamp = System.currentTimeMillis();
+			}
+			else {
+				this.clientSendMessageCount = null;
+			}
 		}

+
 		public String getSessionId() {
 			return this.sessionId;
 		}

+		@Override
+		public StompHeaderAccessor getConnectHeaders() {
+			return this.connectHeaders;
+		}
+
 		@Nullable
 		protected TcpConnection<byte[]> getTcpConnection() {
 			return this.tcpConnection;
@@ -722,31 +775,31 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 			initHeartbeats(connectedHeaders);
 		}

-		private void initHeartbeats(StompHeaderAccessor connectedHeaders) {
-			if (this.isRemoteClientSession) {
-				return;
+		protected void initHeartbeats(StompHeaderAccessor connectedHeaders) {
+			if (taskScheduler != null) {
+				long interval = connectedHeaders.getHeartbeat()[1];
+				this.clientSendInterval = Math.max(interval, this.clientSendInterval);
 			}
+		}

-			TcpConnection<byte[]> con = this.tcpConnection;
-			Assert.state(con != null, "No TcpConnection available");
+		/**
+		 * Whether to forward a heartbeat message in lieu of a message with a non-broker
+		 * destination. This is done if client-side heartbeats are expected and if there
+		 * haven't been any other messages in the current heartbeat period.
+		 * @since 5.3
+		 */
+		protected boolean shouldSendHeartbeatForIgnoredMessage() {
+			return (this.clientSendMessageCount != null && this.clientSendMessageCount.get() == 0);
+		}

-			long clientSendInterval = this.connectHeaders.getHeartbeat()[0];
-			long clientReceiveInterval = this.connectHeaders.getHeartbeat()[1];
-			long serverSendInterval = connectedHeaders.getHeartbeat()[0];
-			long serverReceiveInterval = connectedHeaders.getHeartbeat()[1];
-
-			if (clientSendInterval > 0 && serverReceiveInterval > 0) {
-				long interval = Math.max(clientSendInterval, serverReceiveInterval);
-				con.onWriteInactivity(() ->
-						con.send(HEARTBEAT_MESSAGE).addCallback(
-								result -> {},
-								ex -> handleTcpConnectionFailure(
-										"Failed to forward heartbeat: " + ex.getMessage(), ex)), interval);
-			}
-			if (clientReceiveInterval > 0 && serverSendInterval > 0) {
-				final long interval = Math.max(clientReceiveInterval, serverSendInterval) * HEARTBEAT_MULTIPLIER;
-				con.onReadInactivity(
-						() -> handleTcpConnectionFailure("No messages received in " + interval + " ms.", null), interval);
+		/**
+		 * Reset the clientSendMessageCount if the current heartbeat period has expired.
+		 * @since 5.3
+		 */
+		void updateClientSendMessageCount(long now) {
+			if (this.clientSendMessageCount != null && this.clientSendInterval > (now - clientSendMessageTimestamp)) {
+				this.clientSendMessageCount.set(0);
+				this.clientSendMessageTimestamp = now;
 			}
 		}

@@ -824,6 +877,10 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 				}
 			}

+			if (this.clientSendMessageCount != null) {
+				this.clientSendMessageCount.incrementAndGet();
+			}
+
 			final Message<?> messageToSend = (accessor.isMutable() && accessor.isModified()) ?
 					MessageBuilder.createMessage(message.getPayload(), accessor.getMessageHeaders()) : message;

@@ -911,9 +968,9 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 	}


-	private class SystemStompConnectionHandler extends StompConnectionHandler {
+	private class SystemSessionConnectionHandler extends RelayConnectionHandler {

-		public SystemStompConnectionHandler(StompHeaderAccessor connectHeaders) {
+		public SystemSessionConnectionHandler(StompHeaderAccessor connectHeaders) {
 			super(SYSTEM_SESSION_ID, connectHeaders, false);
 		}

@@ -927,6 +984,30 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 			sendSystemSubscriptions();
 		}

+		protected void initHeartbeats(StompHeaderAccessor connectedHeaders) {
+			TcpConnection<byte[]> con = getTcpConnection();
+			Assert.state(con != null, "No TcpConnection available");
+
+			long clientSendInterval = getConnectHeaders().getHeartbeat()[0];
+			long clientReceiveInterval = getConnectHeaders().getHeartbeat()[1];
+			long serverSendInterval = connectedHeaders.getHeartbeat()[0];
+			long serverReceiveInterval = connectedHeaders.getHeartbeat()[1];
+
+			if (clientSendInterval > 0 && serverReceiveInterval > 0) {
+				long interval = Math.max(clientSendInterval, serverReceiveInterval);
+				con.onWriteInactivity(() ->
+						con.send(HEARTBEAT_MESSAGE).addCallback(
+								result -> {},
+								ex -> handleTcpConnectionFailure(
+										"Failed to forward heartbeat: " + ex.getMessage(), ex)), interval);
+			}
+			if (clientReceiveInterval > 0 && serverSendInterval > 0) {
+				final long interval = Math.max(clientReceiveInterval, serverSendInterval) * HEARTBEAT_MULTIPLIER;
+				con.onReadInactivity(
+						() -> handleTcpConnectionFailure("No messages received in " + interval + " ms.", null), interval);
+			}
+		}
+
 		private void sendSystemSubscriptions() {
 			int i = 0;
 			for (String destination : getSystemSubscriptions().keySet()) {
@@ -1005,9 +1086,27 @@ public class StompBrokerRelayMessageHandler extends AbstractBrokerMessageHandler
 				throw new MessageDeliveryException(message, ex);
 			}
 		}
+
+		@Override
+		protected boolean shouldSendHeartbeatForIgnoredMessage() {
+			return false;
+		}
 	}


+	private class ClientSendMessageCountTask implements Runnable {
+
+		@Override
+		public void run() {
+			long now = System.currentTimeMillis();
+			for (RelayConnectionHandler handler : connectionHandlers.values()) {
+				handler.updateClientSendMessageCount(now);
+			}
+		}
+	}
+
+
+
 	private static class VoidCallable implements Callable<Void> {

 		@Override
@@ -98,6 +98,14 @@ public abstract class StompClientSupport {
 	 * <p>By default this is set to "10000,10000" but subclasses may override
 	 * that default and for example set it to "0,0" if they require a
 	 * TaskScheduler to be configured first.
+	 * <p><strong>Note:</strong> that a heartbeat is sent only in case of
+	 * inactivity, i.e. when no other messages are sent. This can present a
+	 * challenge when using an external broker since messages with a non-broker
+	 * destination represent activity but aren't actually forwarded to the broker.
+	 * In that case you can configure a `TaskScheduler` through the
+	 * {@link org.springframework.messaging.simp.config.StompBrokerRelayRegistration}
+	 * which ensures a heartbeat is forwarded to the broker also when only
+	 * messages with a non-broker destination are sent.
 	 * @param heartbeat the value for the CONNECT "heart-beat" header
 	 * @see <a href="https://stomp.github.io/stomp-specification-1.2.html#Heart-beating">
 	 * https://stomp.github.io/stomp-specification-1.2.html#Heart-beating</a>
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2002-2020 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.messaging.simp.stomp;
+
+import org.springframework.messaging.simp.SimpMessageHeaderAccessor;
+import org.springframework.messaging.tcp.TcpConnectionHandler;
+
+/**
+ * A {@link TcpConnectionHandler} for use with STOMP connections, exposing
+ * further information about the connection.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.3
+ * @param <P> the type of payload for inbound and outbound messages
+ */
+public interface StompTcpConnectionHandler<P> extends TcpConnectionHandler<P> {
+
+	/**
+	 * Return the {@link SimpMessageHeaderAccessor#getSessionId() sessionId}
+	 * associated with the STOMP connection.
+	 */
+	String getSessionId();
+
+	/**
+	 * Return the headers that will be sent in the STOMP CONNECT frame.
+	 */
+	StompHeaderAccessor getConnectHeaders();
+
+}
@@ -18,6 +18,7 @@ package org.springframework.messaging.simp.user;

 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import java.security.Principal;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -310,6 +311,12 @@ public class MultiServerUserRegistry implements SimpUserRegistry, SmartApplicati
 			return this.name;
 		}

+		@Nullable
+		@Override
+		public Principal getPrincipal() {
+			return null;
+		}
+
 		@Override
 		public boolean hasSessions() {
 			if (this.sessionLookup != null) {
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -16,6 +16,7 @@

 package org.springframework.messaging.simp.user;

+import java.security.Principal;
 import java.util.Set;

 import org.springframework.lang.Nullable;
@@ -33,6 +34,15 @@ public interface SimpUser {
 	 */
 	String getName();

+	/**
+	 * Return the user associated with the session, if available. Typically, the
+	 * user information is available unless the user is connected to a different
+	 * server in a multi-server user registry scenario.
+	 * @since 5.3
+	 */
+	@Nullable
+	Principal getPrincipal();
+
 	/**
 	 * Whether the user has any sessions.
 	 */
@@ -186,7 +186,7 @@ public class ReactorNettyTcpClient<P> implements TcpOperations<P> {
 			return handleShuttingDownConnectFailure(handler);
 		}

-		Mono<Void> connectMono = this.tcpClient
+		Mono<Void> connectMono = extendTcpClient(this.tcpClient, handler)
 				.handle(new ReactorNettyHandler(handler))
 				.connect()
 				.doOnError(handler::afterConnectFailure)
@@ -195,6 +195,19 @@ public class ReactorNettyTcpClient<P> implements TcpOperations<P> {
 		return new MonoToListenableFutureAdapter<>(connectMono);
 	}

+	/**
+	 * Provides an opportunity to initialize the {@link TcpClient} for the given
+	 * {@link TcpConnectionHandler} which may implement sub-interfaces such as
+	 * {@link org.springframework.messaging.simp.stomp.StompTcpConnectionHandler}
+	 * that expose further information.
+	 * @param tcpClient the candidate TcpClient
+	 * @param handler the handler for the TCP connection
+	 * @return the same handler or an updated instance
+	 */
+	protected TcpClient extendTcpClient(TcpClient tcpClient, TcpConnectionHandler<P> handler) {
+		return tcpClient;
+	}
+
 	@Override
 	public ListenableFuture<Void> connect(TcpConnectionHandler<P> handler, ReconnectStrategy strategy) {
 		Assert.notNull(handler, "TcpConnectionHandler is required");
@@ -207,7 +220,7 @@ public class ReactorNettyTcpClient<P> implements TcpOperations<P> {
 		// Report first connect to the ListenableFuture
 		CompletableFuture<Void> connectFuture = new CompletableFuture<>();

-		this.tcpClient
+		extendTcpClient(this.tcpClient, handler)
 				.handle(new ReactorNettyHandler(handler))
 				.connect()
 				.doOnNext(conn -> connectFuture.complete(null))
@@ -274,8 +274,7 @@ public class StompBrokerRelayMessageHandlerIntegrationTests {
 		}

 		public void expectMessages(MessageExchange... messageExchanges) throws InterruptedException {
-			List<MessageExchange> expectedMessages =
-					new ArrayList<>(Arrays.<MessageExchange>asList(messageExchanges));
+			List<MessageExchange> expectedMessages = new ArrayList<>(Arrays.asList(messageExchanges));
 			while (expectedMessages.size() > 0) {
 				Message<?> message = this.queue.poll(10000, TimeUnit.MILLISECONDS);
 				assertThat(message).as("Timed out waiting for messages, expected [" + expectedMessages + "]").isNotNull();
@@ -451,7 +450,7 @@ public class StompBrokerRelayMessageHandlerIntegrationTests {
 		@Override
 		public final boolean match(Message<?> message) {
 			StompHeaderAccessor headers = StompHeaderAccessor.wrap(message);
-			if (!this.command.equals(headers.getCommand()) || (this.sessionId != headers.getSessionId())) {
+			if (!this.command.equals(headers.getCommand()) || !this.sessionId.equals(headers.getSessionId())) {
 				return false;
 			}
 			return matchInternal(headers, message.getPayload());
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -17,7 +17,6 @@
 package org.springframework.messaging.simp.stomp;

 import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.Callable;
@@ -39,10 +38,12 @@ import org.springframework.messaging.tcp.ReconnectStrategy;
 import org.springframework.messaging.tcp.TcpConnection;
 import org.springframework.messaging.tcp.TcpConnectionHandler;
 import org.springframework.messaging.tcp.TcpOperations;
+import org.springframework.scheduling.TaskScheduler;
 import org.springframework.util.concurrent.ListenableFuture;
 import org.springframework.util.concurrent.ListenableFutureTask;

 import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.verify;

@@ -59,6 +60,8 @@ class StompBrokerRelayMessageHandlerTests {

 	private StubTcpOperations tcpClient;

+	ArgumentCaptor<Runnable> messageCountTaskCaptor = ArgumentCaptor.forClass(Runnable.class);
+

 	@BeforeEach
 	void setup() {
@@ -66,7 +69,7 @@ class StompBrokerRelayMessageHandlerTests {
 		this.outboundChannel = new StubMessageChannel();

 		this.brokerRelay = new StompBrokerRelayMessageHandler(new StubMessageChannel(),
-				this.outboundChannel, new StubMessageChannel(), Arrays.asList("/topic")) {
+				this.outboundChannel, new StubMessageChannel(), Collections.singletonList("/topic")) {

 			@Override
 			protected void startInternal() {
@@ -77,6 +80,8 @@ class StompBrokerRelayMessageHandlerTests {

 		this.tcpClient = new StubTcpOperations();
 		this.brokerRelay.setTcpClient(this.tcpClient);
+
+		this.brokerRelay.setTaskScheduler(mock(TaskScheduler.class));
 	}


@@ -127,18 +132,51 @@ class StompBrokerRelayMessageHandlerTests {

 	@Test
 	void destinationExcluded() {
+		this.brokerRelay.start();
+		this.brokerRelay.handleMessage(connectMessage("sess1", "joe"));
+
+		SimpMessageHeaderAccessor accessor = StompHeaderAccessor.create(StompCommand.CONNECTED);
+		accessor.setLeaveMutable(true);
+		this.tcpClient.handleMessage(MessageBuilder.createMessage(new byte[0], accessor.getMessageHeaders()));
+
+		accessor = SimpMessageHeaderAccessor.create(SimpMessageType.MESSAGE);
+		accessor.setSessionId("sess1");
+		accessor.setDestination("/user/daisy/foo");
+		this.brokerRelay.handleMessage(MessageBuilder.createMessage(new byte[0], accessor.getMessageHeaders()));
+
+		assertThat(this.tcpClient.getSentMessages().size()).isEqualTo(2);
+		StompHeaderAccessor headers = this.tcpClient.getSentHeaders(0);
+		assertThat(headers.getCommand()).isEqualTo(StompCommand.CONNECT);
+		assertThat(headers.getSessionId()).isEqualTo(StompBrokerRelayMessageHandler.SYSTEM_SESSION_ID);
+
+		headers = this.tcpClient.getSentHeaders(1);
+		assertThat(headers.getCommand()).isEqualTo(StompCommand.CONNECT);
+		assertThat(headers.getSessionId()).isEqualTo("sess1");
+	}
+
+	@Test // gh-22822
+	void destinationExcludedWithHeartbeat() {
+		Message<byte[]> connectMessage = connectMessage("sess1", "joe");
+		MessageHeaderAccessor.getAccessor(connectMessage, StompHeaderAccessor.class).setHeartbeat(10000, 10000);

 		this.brokerRelay.start();
+		this.brokerRelay.handleMessage(connectMessage);

-		SimpMessageHeaderAccessor headers = SimpMessageHeaderAccessor.create(SimpMessageType.MESSAGE);
-		headers.setSessionId("sess1");
-		headers.setDestination("/user/daisy/foo");
-		this.brokerRelay.handleMessage(MessageBuilder.createMessage(new byte[0], headers.getMessageHeaders()));
+		SimpMessageHeaderAccessor accessor = StompHeaderAccessor.create(StompCommand.CONNECTED);
+		accessor.setLeaveMutable(true);
+		this.tcpClient.handleMessage(MessageBuilder.createMessage(new byte[0], accessor.getMessageHeaders()));

-		assertThat(this.tcpClient.getSentMessages().size()).isEqualTo(1);
-		StompHeaderAccessor headers1 = this.tcpClient.getSentHeaders(0);
-		assertThat(headers1.getCommand()).isEqualTo(StompCommand.CONNECT);
-		assertThat(headers1.getSessionId()).isEqualTo(StompBrokerRelayMessageHandler.SYSTEM_SESSION_ID);
+		// Run the messageCountTask to clear the message count
+		verify(this.brokerRelay.getTaskScheduler()).scheduleWithFixedDelay(this.messageCountTaskCaptor.capture(), eq(5000L));
+		this.messageCountTaskCaptor.getValue().run();
+
+		accessor = SimpMessageHeaderAccessor.create(SimpMessageType.MESSAGE);
+		accessor.setSessionId("sess1");
+		accessor.setDestination("/user/daisy/foo");
+		this.brokerRelay.handleMessage(MessageBuilder.createMessage(new byte[0], accessor.getMessageHeaders()));
+
+		assertThat(this.tcpClient.getSentMessages().size()).isEqualTo(3);
+		assertThat(this.tcpClient.getSentHeaders(2).getMessageType()).isEqualTo(SimpMessageType.HEARTBEAT);
 	}

 	@Test
@@ -227,6 +265,7 @@ class StompBrokerRelayMessageHandlerTests {
 		StompHeaderAccessor headers = StompHeaderAccessor.create(StompCommand.CONNECT);
 		headers.setSessionId(sessionId);
 		headers.setUser(new TestPrincipal(user));
+		headers.setLeaveMutable(true);
 		return MessageBuilder.createMessage(new byte[0], headers.getMessageHeaders());
 	}

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2017 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
@@ -16,11 +16,14 @@

 package org.springframework.messaging.simp.user;

+import java.security.Principal;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Map;
 import java.util.Set;

+import org.springframework.lang.Nullable;
+
 /**
 * @author Rossen Stoyanchev
 */
@@ -41,6 +44,12 @@ public class TestSimpUser implements SimpUser {
 		return name;
 	}

+	@Nullable
+	@Override
+	public Principal getPrincipal() {
+		return null;
+	}
+
 	@Override
 	public Set<SimpSession> getSessions() {
 		return new HashSet<>(this.sessions.values());
@@ -0,0 +1,214 @@
+/*
+ * Copyright 2002-2019 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.messaging.converter
+
+import kotlinx.serialization.Serializable
+import org.assertj.core.api.Assertions
+import org.junit.jupiter.api.Test
+import org.springframework.core.MethodParameter
+import org.springframework.messaging.support.MessageBuilder
+import java.nio.charset.StandardCharsets
+import kotlin.reflect.typeOf
+
+@Suppress("UsePropertyAccessSyntax")
+class KotlinSerializationJsonMessageConverterTests {
+
+	private val converter = KotlinSerializationJsonMessageConverter()
+
+	@Test
+	fun readObject() {
+		val payload = """
+			{
+				"bytes": [
+					1,
+					2
+				],
+				"array": [
+					"Foo",
+					"Bar"
+				],
+				"number": 42,
+				"string": "Foo",
+				"bool": true,
+				"fraction": 42
+			}
+		""".trimIndent()
+		val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
+		val result = converter.fromMessage(message, SerializableBean::class.java) as SerializableBean
+
+		Assertions.assertThat(result.bytes).containsExactly(0x1, 0x2)
+		Assertions.assertThat(result.array).containsExactly("Foo", "Bar")
+		Assertions.assertThat(result.number).isEqualTo(42)
+		Assertions.assertThat(result.string).isEqualTo("Foo")
+		Assertions.assertThat(result.bool).isTrue()
+		Assertions.assertThat(result.fraction).isEqualTo(42.0f)
+	}
+
+	@Test
+	@Suppress("UNCHECKED_CAST")
+	fun readArrayOfObjects() {
+		val payload = """
+			[
+				{
+					"bytes": [
+						1,
+						2
+					],
+					"array": [
+						"Foo",
+						"Bar"
+					],
+					"number": 42,
+					"string": "Foo",
+					"bool": true,
+					"fraction": 42
+				}
+			]
+		""".trimIndent()
+		val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
+		val result = converter.fromMessage(message, Array<SerializableBean>::class.java) as Array<SerializableBean>
+
+		Assertions.assertThat(result).hasSize(1)
+		Assertions.assertThat(result[0].bytes).containsExactly(0x1, 0x2)
+		Assertions.assertThat(result[0].array).containsExactly("Foo", "Bar")
+		Assertions.assertThat(result[0].number).isEqualTo(42)
+		Assertions.assertThat(result[0].string).isEqualTo("Foo")
+		Assertions.assertThat(result[0].bool).isTrue()
+		Assertions.assertThat(result[0].fraction).isEqualTo(42.0f)
+	}
+
+	@Test
+	@Suppress("UNCHECKED_CAST")
+	@ExperimentalStdlibApi
+	fun readGenericCollection() {
+		val payload = """
+			[
+				{
+					"bytes": [
+						1,
+						2
+					],
+					"array": [
+						"Foo",
+						"Bar"
+					],
+					"number": 42,
+					"string": "Foo",
+					"bool": true,
+					"fraction": 42
+				}
+			]
+		""".trimIndent()
+		val method = javaClass.getDeclaredMethod("handleList", List::class.java)
+		val param = MethodParameter(method, 0)
+		val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
+		val result = converter.fromMessage(message, typeOf<List<SerializableBean>>()::class.java, param) as List<SerializableBean>
+
+		Assertions.assertThat(result).hasSize(1)
+		Assertions.assertThat(result[0].bytes).containsExactly(0x1, 0x2)
+		Assertions.assertThat(result[0].array).containsExactly("Foo", "Bar")
+		Assertions.assertThat(result[0].number).isEqualTo(42)
+		Assertions.assertThat(result[0].string).isEqualTo("Foo")
+		Assertions.assertThat(result[0].bool).isTrue()
+		Assertions.assertThat(result[0].fraction).isEqualTo(42.0f)
+	}
+
+	@Test
+	fun readFailsOnInvalidJson() {
+		val payload = """
+			this is an invalid JSON document
+		""".trimIndent()
+
+		val message = MessageBuilder.withPayload(payload.toByteArray(StandardCharsets.UTF_8)).build()
+		Assertions.assertThatExceptionOfType(MessageConversionException::class.java).isThrownBy {
+			converter.fromMessage(message, SerializableBean::class.java)
+		}
+	}
+
+	@Test
+	fun writeObject() {
+		val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, "Foo", true, 42.0f)
+		val message = converter.toMessage(serializableBean, null)
+		val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
+
+		Assertions.assertThat(result)
+				.contains("\"bytes\":[1,2]")
+				.contains("\"array\":[\"Foo\",\"Bar\"]")
+				.contains("\"number\":42")
+				.contains("\"string\":\"Foo\"")
+				.contains("\"bool\":true")
+				.contains("\"fraction\":42.0")
+	}
+
+	@Test
+	fun writeObjectWithNullableProperty() {
+		val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, null, true, 42.0f)
+		val message = converter.toMessage(serializableBean, null)
+		val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
+
+		Assertions.assertThat(result)
+				.contains("\"bytes\":[1,2]")
+				.contains("\"array\":[\"Foo\",\"Bar\"]")
+				.contains("\"number\":42")
+				.contains("\"string\":null")
+				.contains("\"bool\":true")
+				.contains("\"fraction\":42.0")
+	}
+
+	@Test
+	fun writeArrayOfObjects() {
+		val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, "Foo", true, 42.0f)
+		val expectedJson = """
+			[{"bytes":[1,2],"array":["Foo","Bar"],"number":42,"string":"Foo","bool":true,"fraction":42.0}]
+		""".trimIndent()
+
+		val message = converter.toMessage(arrayOf(serializableBean), null)
+		val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
+
+		Assertions.assertThat(result).isEqualTo(expectedJson)
+	}
+
+	@Test
+	@ExperimentalStdlibApi
+	fun writeGenericCollection() {
+		val serializableBean = SerializableBean(byteArrayOf(0x1, 0x2), arrayOf("Foo", "Bar"), 42, "Foo", true, 42.0f)
+		val expectedJson = """
+			[{"bytes":[1,2],"array":["Foo","Bar"],"number":42,"string":"Foo","bool":true,"fraction":42.0}]
+		""".trimIndent()
+
+		val method = javaClass.getDeclaredMethod("handleList", List::class.java)
+		val param = MethodParameter(method, 0)
+		val message = converter.toMessage(arrayListOf(serializableBean), null, param)
+		val result = String((message!!.payload as ByteArray), StandardCharsets.UTF_8)
+
+		Assertions.assertThat(result).isEqualTo(expectedJson)
+	}
+
+	@Suppress("UNUSED_PARAMETER")
+	fun handleList(payload: List<SerializableBean>) {}
+
+	@Serializable
+	@Suppress("ArrayInDataClass")
+	data class SerializableBean(
+			val bytes: ByteArray,
+			val array: Array<String>,
+			val number: Int,
+			val string: String?,
+			val bool: Boolean,
+			val fraction: Float
+	)
+}
@@ -29,8 +29,6 @@ import io.r2dbc.spi.R2dbcTimeoutException;
 import io.r2dbc.spi.R2dbcTransientException;
 import io.r2dbc.spi.R2dbcTransientResourceException;
 import io.r2dbc.spi.Wrapped;
-import org.apache.commons.logging.Log;
-import org.apache.commons.logging.LogFactory;
 import reactor.core.publisher.Mono;

 import org.springframework.core.Ordered;
@@ -69,11 +67,6 @@ public abstract class ConnectionFactoryUtils {
 	 */
 	public static final int CONNECTION_SYNCHRONIZATION_ORDER = 1000;

-	private static final Log logger = LogFactory.getLog(ConnectionFactoryUtils.class);
-
-
-	private ConnectionFactoryUtils() {}
-

 	/**
 	 * Obtain a {@link Connection} from the given {@link ConnectionFactory}.
@@ -112,48 +105,34 @@ public abstract class ConnectionFactoryUtils {
 			if (conHolder != null && (conHolder.hasConnection() || conHolder.isSynchronizedWithTransaction())) {
 				conHolder.requested();
 				if (!conHolder.hasConnection()) {
-
-					if (logger.isDebugEnabled()) {
-						logger.debug("Fetching resumed R2DBC Connection from ConnectionFactory");
-					}
 					return fetchConnection(connectionFactory).doOnNext(conHolder::setConnection);
 				}
 				return Mono.just(conHolder.getConnection());
 			}
 			// Else we either got no holder or an empty thread-bound holder here.

-			if (logger.isDebugEnabled()) {
-				logger.debug("Fetching R2DBC Connection from ConnectionFactory");
-			}
-
 			Mono<Connection> con = fetchConnection(connectionFactory);
-
 			if (synchronizationManager.isSynchronizationActive()) {
-
-				return con.flatMap(connection -> {
-					return Mono.just(connection).doOnNext(conn -> {
-
-						// Use same Connection for further R2DBC actions within the transaction.
-						// Thread-bound object will get removed by synchronization at transaction completion.
-						ConnectionHolder holderToUse = conHolder;
-						if (holderToUse == null) {
-							holderToUse = new ConnectionHolder(conn);
-						}
-						else {
-							holderToUse.setConnection(conn);
-						}
-						holderToUse.requested();
-						synchronizationManager
-								.registerSynchronization(new ConnectionSynchronization(holderToUse, connectionFactory));
-						holderToUse.setSynchronizedWithTransaction(true);
-						if (holderToUse != conHolder) {
-							synchronizationManager.bindResource(connectionFactory, holderToUse);
-						}
-					})      // Unexpected exception from external delegation call -> close Connection and rethrow.
-					.onErrorResume(e -> releaseConnection(connection, connectionFactory).then(Mono.error(e)));
-				});
+				return con.flatMap(connection -> Mono.just(connection).doOnNext(conn -> {
+					// Use same Connection for further R2DBC actions within the transaction.
+					// Thread-bound object will get removed by synchronization at transaction completion.
+					ConnectionHolder holderToUse = conHolder;
+					if (holderToUse == null) {
+						holderToUse = new ConnectionHolder(conn);
+					}
+					else {
+						holderToUse.setConnection(conn);
+					}
+					holderToUse.requested();
+					synchronizationManager
+							.registerSynchronization(new ConnectionSynchronization(holderToUse, connectionFactory));
+					holderToUse.setSynchronizedWithTransaction(true);
+					if (holderToUse != conHolder) {
+						synchronizationManager.bindResource(connectionFactory, holderToUse);
+					}
+				})      // Unexpected exception from external delegation call -> close Connection and rethrow.
+				.onErrorResume(e -> releaseConnection(connection, connectionFactory).then(Mono.error(e))));
 			}
-
 			return con;
 		}).onErrorResume(NoTransactionException.class, e -> Mono.from(connectionFactory.create()));
 	}
@@ -356,9 +335,7 @@ public abstract class ConnectionFactoryUtils {
 		@Override
 		public Mono<Void> suspend() {
 			if (this.holderActive) {
-				return TransactionSynchronizationManager.forCurrentTransaction()
-						.flatMap(synchronizationManager -> {
-
+				return TransactionSynchronizationManager.forCurrentTransaction().flatMap(synchronizationManager -> {
 					synchronizationManager.unbindResource(this.connectionFactory);
 					if (this.connectionHolder.hasConnection() && !this.connectionHolder.isOpen()) {
 						// Release Connection on suspend if the application doesn't keep
@@ -371,7 +348,6 @@ public abstract class ConnectionFactoryUtils {
 					return Mono.empty();
 				});
 			}
-
 			return Mono.empty();
 		}

@@ -388,11 +364,10 @@ public abstract class ConnectionFactoryUtils {

 		@Override
 		public Mono<Void> beforeCompletion() {
-			// Release Connection early if the holder is not open anymore
-			// (that is, not used by another resource
-			// that has its own cleanup via transaction synchronization),
-			// to avoid issues with strict transaction implementations that expect
-			// the close call before transaction completion.
+			// Release Connection early if the holder is not open anymore (that is,
+			// not used by another resource that has its own cleanup via transaction
+			// synchronization), to avoid issues with strict transaction implementations
+			// that expect the close call before transaction completion.
 			if (!this.connectionHolder.isOpen()) {
 				return TransactionSynchronizationManager.forCurrentTransaction().flatMap(synchronizationManager -> {
 					synchronizationManager.unbindResource(this.connectionFactory);
@@ -414,8 +389,7 @@ public abstract class ConnectionFactoryUtils {
 			if (this.holderActive) {
 				// The bound ConnectionHolder might not be available anymore,
 				// since afterCompletion might get called from a different thread.
-				return TransactionSynchronizationManager.forCurrentTransaction()
-						.flatMap(synchronizationManager -> {
+				return TransactionSynchronizationManager.forCurrentTransaction().flatMap(synchronizationManager -> {
 					synchronizationManager.unbindResourceIfPossible(this.connectionFactory);
 					this.holderActive = false;
 					if (this.connectionHolder.hasConnection()) {
@@ -426,7 +400,6 @@ public abstract class ConnectionFactoryUtils {
 					return Mono.empty();
 				});
 			}
-
 			this.connectionHolder.reset();
 			return Mono.empty();
 		}
@@ -107,8 +107,6 @@ public abstract class ScriptUtils {

 	private static final Log logger = LogFactory.getLog(ScriptUtils.class);

-	// utility constructor
-	private ScriptUtils() {}

 	/**
 	 * Split an SQL script into separate statements delimited by the provided
@@ -335,14 +333,11 @@ public abstract class ScriptUtils {

 		return DataBufferUtils.join(DataBufferUtils.read(resource.getResource(), dataBufferFactory, 8192))
 				.handle((it, sink) -> {
-
 					try (InputStream is = it.asInputStream()) {
-
-						InputStreamReader in = resource.getCharset() != null ? new InputStreamReader(is, resource.getCharset())
-								: new InputStreamReader(is);
+						InputStreamReader in = (resource.getCharset() != null ?
+								new InputStreamReader(is, resource.getCharset()) : new InputStreamReader(is));
 						LineNumberReader lnr = new LineNumberReader(in);
 						String script = readScript(lnr, commentPrefixes, separator, blockCommentEndDelimiter);
-
 						sink.next(script);
 						sink.complete();
 					}
@@ -548,9 +543,9 @@ public abstract class ScriptUtils {
 	 * @see org.springframework.r2dbc.connection.ConnectionFactoryUtils#releaseConnection
 	 */
 	public static Mono<Void> executeSqlScript(Connection connection, EncodedResource resource,
-			DataBufferFactory dataBufferFactory, boolean continueOnError, boolean ignoreFailedDrops, String commentPrefix,
-			@Nullable String separator, String blockCommentStartDelimiter, String blockCommentEndDelimiter)
-			throws ScriptException {
+			DataBufferFactory dataBufferFactory, boolean continueOnError, boolean ignoreFailedDrops,
+			String commentPrefix, @Nullable String separator, String blockCommentStartDelimiter,
+			String blockCommentEndDelimiter) throws ScriptException {

 		return executeSqlScript(connection, resource, dataBufferFactory, continueOnError,
 				ignoreFailedDrops, new String[] { commentPrefix }, separator,
@@ -587,10 +582,10 @@ public abstract class ScriptUtils {
 	 * @see org.springframework.r2dbc.connection.ConnectionFactoryUtils#getConnection
 	 * @see org.springframework.r2dbc.connection.ConnectionFactoryUtils#releaseConnection
 	 */
-	public static Mono<Void> executeSqlScript(Connection connection, EncodedResource resource, DataBufferFactory dataBufferFactory,
-			boolean continueOnError,
-			boolean ignoreFailedDrops, String[] commentPrefixes, @Nullable String separator,
-			String blockCommentStartDelimiter, String blockCommentEndDelimiter) throws ScriptException {
+	public static Mono<Void> executeSqlScript(Connection connection, EncodedResource resource,
+			DataBufferFactory dataBufferFactory, boolean continueOnError, boolean ignoreFailedDrops,
+			String[] commentPrefixes, @Nullable String separator, String blockCommentStartDelimiter,
+			String blockCommentEndDelimiter) throws ScriptException {

 		if (logger.isDebugEnabled()) {
 			logger.debug("Executing SQL script from " + resource);
@@ -622,17 +617,15 @@ public abstract class ScriptUtils {
 		});

 		if (logger.isDebugEnabled()) {
-
 			executeScript = executeScript.doOnComplete(() -> {
-
 				long elapsedTime = System.currentTimeMillis() - startTime;
 				logger.debug("Executed SQL script from " + resource + " in " + elapsedTime + " ms.");
 			});
 		}

 		return executeScript.onErrorMap(ex -> !(ex instanceof ScriptException),
-				ex -> new UncategorizedScriptException("Failed to execute database script from resource [" + resource + "]",
-						ex))
+				ex -> new UncategorizedScriptException(
+						"Failed to execute database script from resource [" + resource + "]", ex))
 				.then();
 	}

@@ -644,22 +637,21 @@ public abstract class ScriptUtils {
 				.collect(Collectors.summingLong(count -> count));

 		if (logger.isDebugEnabled()) {
-			execution = execution.doOnNext(rowsAffected -> logger.debug(rowsAffected + " returned as update count for SQL: " + statement));
+			execution = execution.doOnNext(rowsAffected ->
+					logger.debug(rowsAffected + " returned as update count for SQL: " + statement));
 		}

 		return execution.onErrorResume(ex -> {
-
 			boolean dropStatement = StringUtils.startsWithIgnoreCase(statement.trim(), "drop");
 			if (continueOnError || (dropStatement && ignoreFailedDrops)) {
 				if (logger.isDebugEnabled()) {
-					logger.debug(ScriptStatementFailedException.buildErrorMessage(statement, statementNumber.get(), resource),
-							ex);
+					logger.debug(ScriptStatementFailedException.buildErrorMessage(
+							statement, statementNumber.get(), resource), ex);
 				}
 			}
 			else {
 				return Mono.error(new ScriptStatementFailedException(statement, statementNumber.get(), resource, ex));
 			}
-
 			return Mono.empty();
 		}).then();
 	}
@@ -167,6 +167,7 @@ public abstract class AbstractRoutingConnectionFactory implements ConnectionFact
 	 */
 	protected ConnectionFactory resolveSpecifiedConnectionFactory(Object connectionFactory)
 			throws IllegalArgumentException {
+
 		if (connectionFactory instanceof ConnectionFactory) {
 			return (ConnectionFactory) connectionFactory;
 		}
@@ -174,17 +175,14 @@ public abstract class AbstractRoutingConnectionFactory implements ConnectionFact
 			return this.connectionFactoryLookup.getConnectionFactory((String) connectionFactory);
 		}
 		else {
-			throw new IllegalArgumentException(
-					"Illegal connection factory value - only 'io.r2dbc.spi.ConnectionFactory' and 'String' supported: "
-							+ connectionFactory);
+			throw new IllegalArgumentException("Illegal connection factory value - " +
+					"only 'io.r2dbc.spi.ConnectionFactory' and 'String' supported: " + connectionFactory);
 		}
 	}

 	@Override
 	public Mono<Connection> create() {
-		return determineTargetConnectionFactory() //
-				.map(ConnectionFactory::create) //
-				.flatMap(Mono::from);
+		return determineTargetConnectionFactory().map(ConnectionFactory::create).flatMap(Mono::from);
 	}

 	@Override
@@ -56,7 +56,6 @@ public class MapConnectionFactoryLookup implements ConnectionFactoryLookup {

 	/**
 	 * Create a new instance of the {@link MapConnectionFactoryLookup} class.
-	 *
 	 * @param connectionFactoryName the name under which the supplied {@link ConnectionFactory} is to be added
 	 * @param connectionFactory the {@link ConnectionFactory} to be added
 	 */
--- a/Show More
+++ b/Show More