Add ResponseStatusException

This change adds a ResponseStatusException to associate an exception
with a status code at runtime. Along with that is an
ResponseStatusExceptionHandler that handles ResponseStatusException
by setting the response status.

spring-web-reactive/src/main/java/org/springframework/web/ResponseStatusException.java

@@ -0,0 +1,45 @@
+/*
+ * Copyright 2002-2015 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
+ *
+ *      http://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.web;
+
+import org.springframework.core.NestedRuntimeException;
+import org.springframework.http.HttpStatus;
+
+/**
+ * Exception wrapper to associate an exception with a status code at runtime.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class ResponseStatusException extends NestedRuntimeException {
+
+	private final HttpStatus httpStatus;
+
+
+	public ResponseStatusException(HttpStatus status) {
+		this(status, null);
+	}
+
+	public ResponseStatusException(HttpStatus status, Throwable cause) {
+		super("Request processing failure with status code: " + status, cause);
+		this.httpStatus = status;
+	}
+
+
+	public HttpStatus getHttpStatus() {
+		return this.httpStatus;
+	}
+
+}

spring-web-reactive/src/main/java/org/springframework/web/reactive/ResponseStatusExceptionHandler.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2002-2015 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
+ *
+ *      http://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.web.reactive;
+
+import org.reactivestreams.Publisher;
+import reactor.Publishers;
+
+import org.springframework.http.server.reactive.HttpExceptionHandler;
+import org.springframework.http.server.reactive.ServerHttpRequest;
+import org.springframework.http.server.reactive.ServerHttpResponse;
+import org.springframework.web.ResponseStatusException;
+
+/**
+ * Handle {@link ResponseStatusException} by setting the response status.
+ *
+ * @author Rossen Stoyanchev
+ */
+public class ResponseStatusExceptionHandler implements HttpExceptionHandler {
+
+
+	@Override
+	public Publisher<Void> handle(ServerHttpRequest request, ServerHttpResponse response, Throwable ex) {
+		if (ex instanceof ResponseStatusException) {
+			response.setStatusCode(((ResponseStatusException) ex).getHttpStatus());
+			return response.writeHeaders();
+		}
+		return Publishers.error(ex);
+	}
+
+}