Add JsonConverterDelegate

The JsonConverterDelegate interface replaces usages of
HttpMessageContentConverter to provides the flexibility to use either
message converters or WebFlux codecs.

HttpMessageContentConverter is deprecated, and replaced with a package
private copy (DefaultJsonConverterDelegate) in the
org.springframework.test.json package that is accessible through
a static method on JsonConverterDelegate.

See gh-35737

spring-test/src/main/java/org/springframework/test/http/HttpMessageContentConverter.java

@@ -18,11 +18,13 @@ package org.springframework.test.http;
 
 import java.io.IOException;
 import java.lang.reflect.Type;
+import java.nio.charset.StandardCharsets;
 import java.util.Arrays;
 import java.util.List;
 import java.util.stream.StreamSupport;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpInputMessage;
 import org.springframework.http.MediaType;
 import org.springframework.http.converter.GenericHttpMessageConverter;
@@ -31,6 +33,7 @@ import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.http.converter.SmartHttpMessageConverter;
 import org.springframework.mock.http.MockHttpInputMessage;
 import org.springframework.mock.http.MockHttpOutputMessage;
+import org.springframework.test.json.JsonConverterDelegate;
 import org.springframework.util.Assert;
 import org.springframework.util.function.SingletonSupplier;
 
@@ -39,8 +42,10 @@ import org.springframework.util.function.SingletonSupplier;
  *
  * @author Stephane Nicoll
  * @since 6.2
+ * @deprecated in favor of static factory methods in {@link JsonConverterDelegate}
  */
-public class HttpMessageContentConverter {
+@Deprecated(since = "7.0", forRemoval = true)
+public class HttpMessageContentConverter implements JsonConverterDelegate {
 
 	private static final MediaType JSON = MediaType.APPLICATION_JSON;
 
@@ -69,6 +74,19 @@ public class HttpMessageContentConverter {
 	}
 
 
+	@Override
+	public <T> T read(String content, ResolvableType targetType) throws IOException{
+		HttpInputMessage message = new MockHttpInputMessage(content.getBytes(StandardCharsets.UTF_8));
+		message.getHeaders().add(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
+		return convert(message, MediaType.APPLICATION_JSON, targetType);
+	}
+
+	@Override
+	public <T> T map(Object value, ResolvableType targetType) throws IOException {
+		return convertViaJson(value, targetType);
+	}
+
+
 	/**
 	 * Convert the given {@link HttpInputMessage} whose content must match the
 	 * given {@link MediaType} to the requested {@code targetType}.

spring-test/src/main/java/org/springframework/test/json/AbstractJsonContentAssert.java

@@ -20,7 +20,6 @@ import java.io.File;
 import java.io.InputStream;
 import java.lang.reflect.Type;
 import java.nio.charset.Charset;
-import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
 import java.util.function.Consumer;
 
@@ -42,11 +41,6 @@ import org.springframework.core.io.ClassPathResource;
 import org.springframework.core.io.FileSystemResource;
 import org.springframework.core.io.InputStreamResource;
 import org.springframework.core.io.Resource;
-import org.springframework.http.HttpHeaders;
-import org.springframework.http.HttpInputMessage;
-import org.springframework.http.MediaType;
-import org.springframework.mock.http.MockHttpInputMessage;
-import org.springframework.test.http.HttpMessageContentConverter;
 import org.springframework.util.Assert;
 
 /**
@@ -77,7 +71,7 @@ public abstract class AbstractJsonContentAssert<SELF extends AbstractJsonContent
 	private static final Failures failures = Failures.instance();
 
 
-	private final @Nullable HttpMessageContentConverter contentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
 
 	private @Nullable Class<?> resourceLoadClass;
 
@@ -92,7 +86,7 @@ public abstract class AbstractJsonContentAssert<SELF extends AbstractJsonContent
 	 */
 	protected AbstractJsonContentAssert(@Nullable JsonContent actual, Class<?> selfType) {
 		super(actual, selfType);
-		this.contentConverter = (actual != null ? actual.getContentConverter() : null);
+		this.converterDelegate = (actual != null ? actual.getJsonConverterDelegate() : null);
 		this.jsonLoader = new JsonLoader(null, null);
 		as("JSON content");
 	}
@@ -131,13 +125,12 @@ public abstract class AbstractJsonContentAssert<SELF extends AbstractJsonContent
 
 	private <T> T convertToTargetType(Type targetType) {
 		String json = this.actual.getJson();
-		if (this.contentConverter == null) {
+		if (this.converterDelegate == null) {
 			throw new IllegalStateException(
 					"No JSON message converter available to convert %s".formatted(json));
 		}
 		try {
-			return this.contentConverter.convert(fromJson(json), MediaType.APPLICATION_JSON,
-					ResolvableType.forType(targetType));
+			return this.converterDelegate.read(json, ResolvableType.forType(targetType));
 		}
 		catch (Exception ex) {
 			throw failure(new ValueProcessingFailed(json,
@@ -146,12 +139,6 @@ public abstract class AbstractJsonContentAssert<SELF extends AbstractJsonContent
 		}
 	}
 
-	private HttpInputMessage fromJson(String json) {
-		MockHttpInputMessage inputMessage = new MockHttpInputMessage(json.getBytes(StandardCharsets.UTF_8));
-		inputMessage.getHeaders().add(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
-		return inputMessage;
-	}
-
 
 	// JsonPath support
 
@@ -163,7 +150,7 @@ public abstract class AbstractJsonContentAssert<SELF extends AbstractJsonContent
 	 */
 	public JsonPathValueAssert extractingPath(String path) {
 		Object value = new JsonPathValue(path).getValue();
-		return new JsonPathValueAssert(value, path, this.contentConverter);
+		return new JsonPathValueAssert(value, path, this.converterDelegate);
 	}
 
 	/**
@@ -174,7 +161,7 @@ public abstract class AbstractJsonContentAssert<SELF extends AbstractJsonContent
 	 */
 	public SELF hasPathSatisfying(String path, Consumer<AssertProvider<JsonPathValueAssert>> valueRequirements) {
 		Object value = new JsonPathValue(path).assertHasPath();
-		JsonPathValueAssert valueAssert = new JsonPathValueAssert(value, path, this.contentConverter);
+		JsonPathValueAssert valueAssert = new JsonPathValueAssert(value, path, this.converterDelegate);
 		valueRequirements.accept(() -> valueAssert);
 		return this.myself;
 	}

spring-test/src/main/java/org/springframework/test/json/AbstractJsonValueAssert.java

@@ -35,7 +35,6 @@ import org.jspecify.annotations.Nullable;
 
 import org.springframework.core.ResolvableType;
 import org.springframework.http.converter.GenericHttpMessageConverter;
-import org.springframework.test.http.HttpMessageContentConverter;
 import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
@@ -64,14 +63,23 @@ public abstract class AbstractJsonValueAssert<SELF extends AbstractJsonValueAsse
 
 	private final Failures failures = Failures.instance();
 
-	private final @Nullable HttpMessageContentConverter contentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
 
 
-	protected AbstractJsonValueAssert(@Nullable Object actual, Class<?> selfType,
-			@Nullable HttpMessageContentConverter contentConverter) {
+	protected AbstractJsonValueAssert(
+			@Nullable Object actual, Class<?> selfType, @Nullable JsonConverterDelegate converter) {
 
 		super(actual, selfType);
-		this.contentConverter = contentConverter;
+		this.converterDelegate = converter;
+	}
+
+	@SuppressWarnings("removal")
+	@Deprecated(since = "7.0", forRemoval = true)
+	protected AbstractJsonValueAssert(
+			@Nullable Object actual, Class<?> selfType,
+			org.springframework.test.http.@Nullable HttpMessageContentConverter converter) {
+
+		this(actual, selfType, (JsonConverterDelegate) converter);
 	}
 
 
@@ -196,12 +204,12 @@ public abstract class AbstractJsonValueAssert<SELF extends AbstractJsonValueAsse
 	}
 
 	private <T> T convertToTargetType(Type targetType) {
-		if (this.contentConverter == null) {
+		if (this.converterDelegate == null) {
 			throw new IllegalStateException(
 					"No JSON message converter available to convert %s".formatted(actualToString()));
 		}
 		try {
-			return this.contentConverter.convertViaJson(this.actual, ResolvableType.forType(targetType));
+			return this.converterDelegate.map(this.actual, ResolvableType.forType(targetType));
 		}
 		catch (Exception ex) {
 			throw valueProcessingFailed("To convert successfully to:%n  %s%nBut it failed:%n  %s%n"

spring-test/src/main/java/org/springframework/test/json/DefaultJsonConverterDelegate.java

@@ -0,0 +1,151 @@
+/*
+ * Copyright 2002-present 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.test.json;
+
+import java.io.IOException;
+import java.lang.reflect.Type;
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import java.util.stream.StreamSupport;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpInputMessage;
+import org.springframework.http.MediaType;
+import org.springframework.http.converter.GenericHttpMessageConverter;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.converter.HttpMessageNotReadableException;
+import org.springframework.http.converter.SmartHttpMessageConverter;
+import org.springframework.mock.http.MockHttpInputMessage;
+import org.springframework.mock.http.MockHttpOutputMessage;
+import org.springframework.util.Assert;
+import org.springframework.util.function.SingletonSupplier;
+
+/**
+ * Default {@link JsonConverterDelegate} based on {@link HttpMessageConverter}s.
+ *
+ * @author Stephane Nicoll
+ * @author Rossen Stoyanchev
+ * @since 7.0
+ */
+final class DefaultJsonConverterDelegate implements JsonConverterDelegate {
+
+	private static final MediaType JSON = MediaType.APPLICATION_JSON;
+
+	private final List<HttpMessageConverter<?>> messageConverters;
+
+
+	DefaultJsonConverterDelegate(Iterable<HttpMessageConverter<?>> messageConverters) {
+		this.messageConverters = StreamSupport.stream(messageConverters.spliterator(), false).toList();
+		Assert.notEmpty(this.messageConverters, "At least one message converter needs to be specified");
+	}
+
+
+	@Override
+	public <T> T read(String content, ResolvableType targetType) throws IOException{
+		HttpInputMessage message = new MockHttpInputMessage(content.getBytes(StandardCharsets.UTF_8));
+		message.getHeaders().add(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE);
+		return read(message, MediaType.APPLICATION_JSON, targetType);
+	}
+
+	/**
+	 * Convert the given {@link HttpInputMessage} whose content must match the
+	 * given {@link MediaType} to the requested {@code targetType}.
+	 * @param message an input message
+	 * @param mediaType the media type of the input
+	 * @param targetType the target type
+	 * @param <T> the converted object type
+	 * @return a value of the given {@code targetType}
+	 */
+	@SuppressWarnings("unchecked")
+	<T> T read(HttpInputMessage message, MediaType mediaType, ResolvableType targetType)
+			throws IOException, HttpMessageNotReadableException {
+
+		Class<?> contextClass = targetType.getRawClass();
+		SingletonSupplier<Type> javaType = SingletonSupplier.of(targetType::getType);
+		for (HttpMessageConverter<?> messageConverter : this.messageConverters) {
+			if (messageConverter instanceof GenericHttpMessageConverter<?> genericMessageConverter) {
+				Type type = javaType.obtain();
+				if (genericMessageConverter.canRead(type, contextClass, mediaType)) {
+					return (T) genericMessageConverter.read(type, contextClass, message);
+				}
+			}
+			else if (messageConverter instanceof SmartHttpMessageConverter<?> smartMessageConverter) {
+				if (smartMessageConverter.canRead(targetType, mediaType)) {
+					return (T) smartMessageConverter.read(targetType, message, null);
+				}
+			}
+			else {
+				Class<?> targetClass = (contextClass != null ? contextClass : Object.class);
+				if (messageConverter.canRead(targetClass, mediaType)) {
+					HttpMessageConverter<T> simpleMessageConverter = (HttpMessageConverter<T>) messageConverter;
+					Class<? extends T> clazz = (Class<? extends T>) targetClass;
+					return simpleMessageConverter.read(clazz, message);
+				}
+			}
+		}
+		throw new IllegalStateException("No converter found to read [%s] to [%s]".formatted(mediaType, targetType));
+	}
+
+	/**
+	 * Convert the given raw value to the given {@code targetType} by writing
+	 * it first to JSON and reading it back.
+	 * @param value the value to convert
+	 * @param targetType the target type
+	 * @param <T> the converted object type
+	 * @return a value of the given {@code targetType}
+	 */
+	@Override
+	public <T> T map(Object value, ResolvableType targetType) throws IOException {
+		MockHttpOutputMessage outputMessage = writeToJson(value, ResolvableType.forInstance(value));
+		return read(fromHttpOutputMessage(outputMessage), JSON, targetType);
+	}
+
+	@SuppressWarnings({ "rawtypes", "unchecked" })
+	private MockHttpOutputMessage writeToJson(Object value, ResolvableType valueType) throws IOException {
+		MockHttpOutputMessage outputMessage = new MockHttpOutputMessage();
+		Class<?> valueClass = value.getClass();
+		SingletonSupplier<Type> javaType = SingletonSupplier.of(valueType::getType);
+		for (HttpMessageConverter<?> messageConverter : this.messageConverters) {
+			if (messageConverter instanceof GenericHttpMessageConverter genericMessageConverter) {
+				Type type = javaType.obtain();
+				if (genericMessageConverter.canWrite(type, valueClass, JSON)) {
+					genericMessageConverter.write(value, type, JSON, outputMessage);
+					return outputMessage;
+				}
+			}
+			else if (messageConverter instanceof SmartHttpMessageConverter smartMessageConverter) {
+				if (smartMessageConverter.canWrite(valueType, valueClass, JSON)) {
+					smartMessageConverter.write(value, valueType, JSON, outputMessage, null);
+					return outputMessage;
+				}
+			}
+			else if (messageConverter.canWrite(valueClass, JSON)) {
+				((HttpMessageConverter<Object>) messageConverter).write(value, JSON, outputMessage);
+				return outputMessage;
+			}
+		}
+		throw new IllegalStateException("No converter found to convert [%s] to JSON".formatted(valueType));
+	}
+
+	private static HttpInputMessage fromHttpOutputMessage(MockHttpOutputMessage message) {
+		MockHttpInputMessage inputMessage = new MockHttpInputMessage(message.getBodyAsBytes());
+		inputMessage.getHeaders().addAll(message.getHeaders());
+		return inputMessage;
+	}
+
+}

spring-test/src/main/java/org/springframework/test/json/JsonContent.java

@@ -34,19 +34,32 @@ public final class JsonContent implements AssertProvider<JsonContentAssert> {
 
 	private final String json;
 
-	private final @Nullable HttpMessageContentConverter contentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
 
 
 	/**
 	 * Create a new {@code JsonContent} instance with the message converter to
 	 * use to deserialize content.
 	 * @param json the actual JSON content
-	 * @param contentConverter the content converter to use
+	 * @param converterDelegate the content converter to use
 	 */
-	public JsonContent(String json, @Nullable HttpMessageContentConverter contentConverter) {
+	public JsonContent(String json, @Nullable JsonConverterDelegate converterDelegate) {
 		Assert.notNull(json, "JSON must not be null");
 		this.json = json;
-		this.contentConverter = contentConverter;
+		this.converterDelegate = converterDelegate;
+	}
+
+	/**
+	 * Create a new {@code JsonContent} instance with the message converter to
+	 * use to deserialize content.
+	 * @param json the actual JSON content
+	 * @param converter the content converter to use
+	 * @deprecated in favour of {@link #JsonContent(String, JsonConverterDelegate)}
+	 */
+	@SuppressWarnings("removal")
+	@Deprecated(since = "7.0", forRemoval = true)
+	public JsonContent(String json, @Nullable HttpMessageContentConverter converter) {
+		this(json, (JsonConverterDelegate) converter);
 	}
 
 	/**
@@ -54,7 +67,7 @@ public final class JsonContent implements AssertProvider<JsonContentAssert> {
 	 * @param json the actual JSON content
 	 */
 	public JsonContent(String json) {
-		this(json, null);
+		this(json, (JsonConverterDelegate) null);
 	}
 
 
@@ -75,10 +88,21 @@ public final class JsonContent implements AssertProvider<JsonContentAssert> {
 	}
 
 	/**
-	 * Return the {@link HttpMessageContentConverter} to use to deserialize content.
+	 * Return the {@link JsonConverterDelegate} to use to decode JSON content.
+	 * @since 7.0
 	 */
+	public @Nullable JsonConverterDelegate getJsonConverterDelegate() {
+		return this.converterDelegate;
+	}
+
+	/**
+	 * Return the {@link HttpMessageContentConverter} to use to deserialize content.
+	 * @deprecated in favour of {@link #getJsonConverterDelegate()}
+	 */
+	@SuppressWarnings("removal")
+	@Deprecated(since = "7.0", forRemoval = true)
 	@Nullable HttpMessageContentConverter getContentConverter() {
-		return this.contentConverter;
+		return (this.converterDelegate instanceof HttpMessageContentConverter cc ? cc : null);
 	}
 
 	@Override

spring-test/src/main/java/org/springframework/test/json/JsonConverterDelegate.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright 2002-present 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.test.json;
+
+import java.io.IOException;
+
+import org.springframework.core.ResolvableType;
+import org.springframework.http.converter.HttpMessageConverter;
+
+/**
+ * Delegate to abstract JSON type conversion in AssertJ support clases.
+ *
+ * @author Rossen Stoyanchev
+ * @since 7.0
+ */
+public interface JsonConverterDelegate {
+
+	/**
+	 * Convert JSON content to the given {@code targetType}.
+	 * @param content the JSON content
+	 * @param targetType the target type
+	 * @return the decoded object
+	 * @param <T> the target type
+	 */
+	<T> T read(String content, ResolvableType targetType) throws IOException;
+
+	/**
+	 * Map the given Object value to the given {@code targetType}, via
+	 * serialization and deserialization to and from JSON. This is useful for
+	 * mapping generic maps and lists to higher level Objects.
+	 * @param value the value to map
+	 * @param targetType the target tyep
+	 * @return the decoded object
+	 * @param <T> the target type
+	 */
+	<T> T map(Object value, ResolvableType targetType) throws IOException;
+
+
+	/**
+	 * Create a {@link JsonConverterDelegate} from message converters.
+	 * @param candidates the candidates
+	 */
+	static JsonConverterDelegate of(Iterable<HttpMessageConverter<?>> candidates) {
+		return new DefaultJsonConverterDelegate(candidates);
+	}
+
+}

spring-test/src/main/java/org/springframework/test/json/JsonPathValueAssert.java

@@ -19,8 +19,6 @@ package org.springframework.test.json;
 import com.jayway.jsonpath.JsonPath;
 import org.jspecify.annotations.Nullable;
 
-import org.springframework.test.http.HttpMessageContentConverter;
-
 /**
  * AssertJ {@linkplain org.assertj.core.api.Assert assertions} that can be applied
  * to a JSON value produced by evaluating a {@linkplain JsonPath JSON path}
@@ -34,10 +32,8 @@ public class JsonPathValueAssert extends AbstractJsonValueAssert<JsonPathValueAs
 	private final String expression;
 
 
-	JsonPathValueAssert(@Nullable Object actual, String expression,
-			@Nullable HttpMessageContentConverter contentConverter) {
-
-		super(actual, JsonPathValueAssert.class, contentConverter);
+	JsonPathValueAssert(@Nullable Object actual, String expression, @Nullable JsonConverterDelegate converter) {
+		super(actual, JsonPathValueAssert.class, converter);
 		this.expression = expression;
 	}
 

spring-test/src/main/java/org/springframework/test/web/servlet/assertj/AbstractMockHttpServletResponseAssert.java

@@ -26,10 +26,10 @@ import org.assertj.core.api.StringAssert;
 import org.jspecify.annotations.Nullable;
 
 import org.springframework.mock.web.MockHttpServletResponse;
-import org.springframework.test.http.HttpMessageContentConverter;
 import org.springframework.test.json.AbstractJsonContentAssert;
 import org.springframework.test.json.JsonContent;
 import org.springframework.test.json.JsonContentAssert;
+import org.springframework.test.json.JsonConverterDelegate;
 import org.springframework.test.web.UriAssert;
 
 /**
@@ -44,13 +44,23 @@ import org.springframework.test.web.UriAssert;
 public abstract class AbstractMockHttpServletResponseAssert<SELF extends AbstractMockHttpServletResponseAssert<SELF, ACTUAL>, ACTUAL>
 		extends AbstractHttpServletResponseAssert<MockHttpServletResponse, SELF, ACTUAL> {
 
-	private final @Nullable HttpMessageContentConverter contentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
+
 
 	protected AbstractMockHttpServletResponseAssert(
-			@Nullable HttpMessageContentConverter contentConverter, ACTUAL actual, Class<?> selfType) {
+			@Nullable JsonConverterDelegate converterDelegate, ACTUAL actual, Class<?> selfType) {
 
 		super(actual, selfType);
-		this.contentConverter = contentConverter;
+		this.converterDelegate = converterDelegate;
+	}
+
+	@SuppressWarnings("removal")
+	@Deprecated(since = "7.0", forRemoval = true)
+	protected AbstractMockHttpServletResponseAssert(
+			org.springframework.test.http.@Nullable HttpMessageContentConverter converter,
+			ACTUAL actual, Class<?> selfType) {
+
+		this((JsonConverterDelegate) converter, actual, selfType);
 	}
 
 
@@ -93,7 +103,7 @@ public abstract class AbstractMockHttpServletResponseAssert<SELF extends Abstrac
 	 * </code></pre>
 	 */
 	public AbstractJsonContentAssert<?> bodyJson() {
-		return new JsonContentAssert(new JsonContent(readBody(), this.contentConverter));
+		return new JsonContentAssert(new JsonContent(readBody(), this.converterDelegate));
 	}
 
 	private String readBody() {

spring-test/src/main/java/org/springframework/test/web/servlet/assertj/DefaultMvcTestResult.java

@@ -18,7 +18,7 @@ package org.springframework.test.web.servlet.assertj;
 
 import org.jspecify.annotations.Nullable;
 
-import org.springframework.test.http.HttpMessageContentConverter;
+import org.springframework.test.json.JsonConverterDelegate;
 import org.springframework.test.web.servlet.MvcResult;
 
 /**
@@ -33,15 +33,15 @@ final class DefaultMvcTestResult implements MvcTestResult {
 
 	private final @Nullable Exception unresolvedException;
 
-	private final @Nullable HttpMessageContentConverter contentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
 
 
 	DefaultMvcTestResult(@Nullable MvcResult mvcResult, @Nullable Exception unresolvedException,
-			@Nullable HttpMessageContentConverter contentConverter) {
+			@Nullable JsonConverterDelegate converterDelegate) {
 
 		this.mvcResult = mvcResult;
 		this.unresolvedException = unresolvedException;
-		this.contentConverter = contentConverter;
+		this.converterDelegate = converterDelegate;
 	}
 
 
@@ -70,7 +70,7 @@ final class DefaultMvcTestResult implements MvcTestResult {
 	 */
 	@Override
 	public MvcTestResultAssert assertThat() {
-		return new MvcTestResultAssert(this, this.contentConverter);
+		return new MvcTestResultAssert(this, this.converterDelegate);
 	}
 
 }

spring-test/src/main/java/org/springframework/test/web/servlet/assertj/MockMvcTester.java

@@ -30,7 +30,7 @@ import org.springframework.http.HttpMethod;
 import org.springframework.http.converter.HttpMessageConverter;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockMultipartHttpServletRequest;
-import org.springframework.test.http.HttpMessageContentConverter;
+import org.springframework.test.json.JsonConverterDelegate;
 import org.springframework.test.web.servlet.MockMvc;
 import org.springframework.test.web.servlet.MvcResult;
 import org.springframework.test.web.servlet.RequestBuilder;
@@ -132,13 +132,13 @@ public final class MockMvcTester {
 
 	private final MockMvc mockMvc;
 
-	private final @Nullable HttpMessageContentConverter contentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
 
 
-	private MockMvcTester(MockMvc mockMvc, @Nullable HttpMessageContentConverter contentConverter) {
+	private MockMvcTester(MockMvc mockMvc, @Nullable JsonConverterDelegate converter) {
 		Assert.notNull(mockMvc, "mockMVC should not be null");
 		this.mockMvc = mockMvc;
-		this.contentConverter = contentConverter;
+		this.converterDelegate = converter;
 	}
 
 	/**
@@ -232,7 +232,7 @@ public final class MockMvcTester {
 	 * @return a new instance using the specified converters
 	 */
 	public MockMvcTester withHttpMessageConverters(Iterable<HttpMessageConverter<?>> httpMessageConverters) {
-		return new MockMvcTester(this.mockMvc, HttpMessageContentConverter.of(httpMessageConverters));
+		return new MockMvcTester(this.mockMvc, JsonConverterDelegate.of(httpMessageConverters));
 	}
 
 	/**
@@ -374,10 +374,10 @@ public final class MockMvcTester {
 	public MvcTestResult perform(RequestBuilder requestBuilder) {
 		Object result = getMvcResultOrFailure(requestBuilder);
 		if (result instanceof MvcResult mvcResult) {
-			return new DefaultMvcTestResult(mvcResult, null, this.contentConverter);
+			return new DefaultMvcTestResult(mvcResult, null, this.converterDelegate);
 		}
 		else {
-			return new DefaultMvcTestResult(null, (Exception) result, this.contentConverter);
+			return new DefaultMvcTestResult(null, (Exception) result, this.converterDelegate);
 		}
 	}
 
@@ -483,7 +483,7 @@ public final class MockMvcTester {
 
 		@Override
 		public MvcTestResultAssert assertThat() {
-			return new MvcTestResultAssert(exchange(), MockMvcTester.this.contentConverter);
+			return new MvcTestResultAssert(exchange(), MockMvcTester.this.converterDelegate);
 		}
 	}
 
@@ -541,7 +541,7 @@ public final class MockMvcTester {
 
 		@Override
 		public MvcTestResultAssert assertThat() {
-			return new MvcTestResultAssert(exchange(), MockMvcTester.this.contentConverter);
+			return new MvcTestResultAssert(exchange(), MockMvcTester.this.converterDelegate);
 		}
 	}
 

spring-test/src/main/java/org/springframework/test/web/servlet/assertj/MvcTestResultAssert.java

@@ -34,7 +34,7 @@ import org.jspecify.annotations.Nullable;
 
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockHttpServletResponse;
-import org.springframework.test.http.HttpMessageContentConverter;
+import org.springframework.test.json.JsonConverterDelegate;
 import org.springframework.test.web.servlet.MvcResult;
 import org.springframework.test.web.servlet.ResultHandler;
 import org.springframework.test.web.servlet.ResultMatcher;
@@ -51,8 +51,8 @@ import org.springframework.web.servlet.ModelAndView;
  */
 public class MvcTestResultAssert extends AbstractMockHttpServletResponseAssert<MvcTestResultAssert, MvcTestResult> {
 
-	MvcTestResultAssert(MvcTestResult actual, @Nullable HttpMessageContentConverter contentConverter) {
-		super(contentConverter, actual, MvcTestResultAssert.class);
+	MvcTestResultAssert(MvcTestResult actual, @Nullable JsonConverterDelegate converterDelegate) {
+		super(converterDelegate, actual, MvcTestResultAssert.class);
 	}
 
 	@Override

spring-test/src/main/java/org/springframework/test/web/servlet/client/DefaultRestTestClient.java

@@ -39,10 +39,10 @@ import org.springframework.http.client.ClientHttpRequestExecution;
 import org.springframework.http.client.ClientHttpRequestInterceptor;
 import org.springframework.http.client.ClientHttpResponse;
 import org.springframework.http.converter.HttpMessageConverters;
-import org.springframework.test.http.HttpMessageContentConverter;
 import org.springframework.test.json.JsonAssert;
 import org.springframework.test.json.JsonComparator;
 import org.springframework.test.json.JsonCompareMode;
+import org.springframework.test.json.JsonConverterDelegate;
 import org.springframework.test.util.AssertionErrors;
 import org.springframework.test.util.ExceptionCollector;
 import org.springframework.test.util.XmlExpectationsHelper;
@@ -69,7 +69,7 @@ class DefaultRestTestClient implements RestTestClient {
 
 	private final DefaultRestTestClientBuilder<?> restTestClientBuilder;
 
-	private final @Nullable HttpMessageContentConverter messageContentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
 
 	private final AtomicLong requestIndex = new AtomicLong();
 
@@ -81,7 +81,7 @@ class DefaultRestTestClient implements RestTestClient {
 		this.restClient = builder.requestInterceptor(this.wiretapInterceptor).build();
 		this.entityResultConsumer = entityResultConsumer;
 		this.restTestClientBuilder = restTestClientBuilder;
-		this.messageContentConverter = new ConverterCallback(this.restClient).getConverter();
+		this.converterDelegate = new ConverterCallback(this.restClient).getConverter();
 	}
 
 
@@ -138,20 +138,20 @@ class DefaultRestTestClient implements RestTestClient {
 
 	private static class ConverterCallback {
 
-		private @Nullable HttpMessageContentConverter converter;
+		private @Nullable JsonConverterDelegate converter;
 
 		ConverterCallback(RestClient client) {
 			client.mutate()
 					.configureMessageConverters(convertersBuilder -> {
 						HttpMessageConverters converters = convertersBuilder.build();
 						if (converters.iterator().hasNext()) {
-							this.converter = HttpMessageContentConverter.of(converters);
+							this.converter = JsonConverterDelegate.of(converters);
 						}
 					})
 					.build();
 		}
 
-		public @Nullable HttpMessageContentConverter getConverter() {
+		public @Nullable JsonConverterDelegate getConverter() {
 			return this.converter;
 		}
 	}
@@ -290,7 +290,7 @@ class DefaultRestTestClient implements RestTestClient {
 							(request, response) -> {
 								byte[] requestBody = wiretapInterceptor.getRequestContent(this.requestId);
 								return new ExchangeResult(
-										request, response, this.uriTemplate, requestBody, messageContentConverter);
+										request, response, this.uriTemplate, requestBody, converterDelegate);
 							}, false),
 					DefaultRestTestClient.this.entityResultConsumer);
 		}

spring-test/src/main/java/org/springframework/test/web/servlet/client/ExchangeResult.java

@@ -38,7 +38,7 @@ import org.springframework.http.HttpStatus;
 import org.springframework.http.HttpStatusCode;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseCookie;
-import org.springframework.test.http.HttpMessageContentConverter;
+import org.springframework.test.json.JsonConverterDelegate;
 import org.springframework.util.Assert;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
@@ -75,7 +75,7 @@ public class ExchangeResult {
 
 	private final byte[] requestBody;
 
-	private final @Nullable HttpMessageContentConverter messageContentConverter;
+	private final @Nullable JsonConverterDelegate converterDelegate;
 
 	/** Ensure single logging; for example, for expectAll. */
 	private boolean diagnosticsLogged;
@@ -83,7 +83,7 @@ public class ExchangeResult {
 
 	ExchangeResult(
 			HttpRequest request, ConvertibleClientHttpResponse response, @Nullable String uriTemplate,
-			byte[] requestBody, @Nullable HttpMessageContentConverter messageContentConverter) {
+			byte[] requestBody, @Nullable JsonConverterDelegate converter) {
 
 		Assert.notNull(request, "HttpRequest must not be null");
 		Assert.notNull(response, "ClientHttpResponse must not be null");
@@ -91,11 +91,11 @@ public class ExchangeResult {
 		this.clientResponse = response;
 		this.uriTemplate = uriTemplate;
 		this.requestBody = requestBody;
-		this.messageContentConverter = messageContentConverter;
+		this.converterDelegate = converter;
 	}
 
 	ExchangeResult(ExchangeResult result) {
-		this(result.request, result.clientResponse, result.uriTemplate, result.requestBody, result.messageContentConverter);
+		this(result.request, result.clientResponse, result.uriTemplate, result.requestBody, result.converterDelegate);
 		this.diagnosticsLogged = result.diagnosticsLogged;
 	}
 
@@ -202,11 +202,11 @@ public class ExchangeResult {
 	}
 
 	/**
-	 * Return a content converter that delegates to the configured HTTP message converters.
+	 * Return a {@link JsonConverterDelegate} based on the configured HTTP message converters.
 	 * Mainly for internal use from AssertJ support.
 	 */
-	public @Nullable HttpMessageContentConverter getMessageContentConverter() {
-		return this.messageContentConverter;
+	public @Nullable JsonConverterDelegate getConverterDelegate() {
+		return this.converterDelegate;
 	}
 
 	/**

spring-test/src/main/java/org/springframework/test/web/servlet/client/assertj/RestTestClientResponseAssert.java

@@ -342,7 +342,7 @@ public class RestTestClientResponseAssert
 	 * </code></pre>
 	 */
 	public AbstractJsonContentAssert<?> bodyJson() {
-		return new JsonContentAssert(new JsonContent(readBody(), getExchangeResult().getMessageContentConverter()));
+		return new JsonContentAssert(new JsonContent(readBody(), getExchangeResult().getConverterDelegate()));
 	}
 
 	private String readBody() {