Add ResponseBodyInterceptor

This change introduces a new ResponseBodyInterceptor interface that can
be used to modify the response after @responsebody or ResponseEntity
methods but before the body is actually written to the response with the
selected HttpMessageConverter.

The RequestMappingHandlerAdapter and ExceptionHandlerExceptionResolver
each have a property to configure such interceptors. In addition both
RequestMappingHandlerAdapter and ExceptionHandlerExceptionResolver
detect if any @ControllerAdvice bean implements ResponseBodyInterceptor
and use it accordingly.

Issue: SPR-10859

Author: rstoyanchev

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/AbstractMessageConverterMethodProcessor.java

@@ -55,16 +55,24 @@ public abstract class AbstractMessageConverterMethodProcessor extends AbstractMe
 
 	private final ContentNegotiationManager contentNegotiationManager;
 
+	private final ResponseBodyInterceptorChain interceptorChain;
+
 
 	protected AbstractMessageConverterMethodProcessor(List<HttpMessageConverter<?>> messageConverters) {
 		this(messageConverters, null);
 	}
 
 	protected AbstractMessageConverterMethodProcessor(List<HttpMessageConverter<?>> messageConverters,
 			ContentNegotiationManager manager) {
+		this(messageConverters, manager, null);
+	}
+
+	protected AbstractMessageConverterMethodProcessor(List<HttpMessageConverter<?>> messageConverters,
+			ContentNegotiationManager manager, List<Object> responseBodyInterceptors) {
 
 		super(messageConverters);
 		this.contentNegotiationManager = (manager != null ? manager : new ContentNegotiationManager());
+		this.interceptorChain = new ResponseBodyInterceptorChain(responseBodyInterceptors);
 	}
 
 
@@ -152,6 +160,9 @@ else if (mediaType.equals(MediaType.ALL) || mediaType.equals(MEDIA_TYPE_APPLICAT
 					}
 				}
 				if (messageConverter.canWrite(returnValueClass, selectedMediaType)) {
+					returnValue = this.interceptorChain.invoke(returnValue, selectedMediaType,
+							(Class<HttpMessageConverter<T>>) messageConverter.getClass(),
+							returnType, inputMessage, outputMessage);
 					((HttpMessageConverter<T>) messageConverter).write(returnValue, selectedMediaType, outputMessage);
 					if (logger.isDebugEnabled()) {
 						logger.debug("Written [" + returnValue + "] as \"" + selectedMediaType + "\" using [" +

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ExceptionHandlerExceptionResolver.java

@@ -79,6 +79,9 @@ public class ExceptionHandlerExceptionResolver extends AbstractHandlerMethodExce
 
 	private ContentNegotiationManager contentNegotiationManager = new ContentNegotiationManager();
 
+	private final List<Object> responseBodyInterceptors = new ArrayList<Object>();
+
+
 	private final Map<Class<?>, ExceptionHandlerMethodResolver> exceptionHandlerCache =
 			new ConcurrentHashMap<Class<?>, ExceptionHandlerMethodResolver>(64);
 
@@ -106,6 +109,19 @@ public ExceptionHandlerExceptionResolver() {
 		this.messageConverters.add(new AllEncompassingFormHttpMessageConverter());
 	}
 
+	/**
+	 * Add one or more interceptors to be invoked after the execution of a controller
+	 * method annotated with {@code @ResponseBody} or returning {@code ResponseEntity}
+	 * but before the body is written to the response with the selected
+	 * {@code HttpMessageConverter}.
+	 */
+	public void setResponseBodyInterceptors(List<ResponseBodyInterceptor> responseBodyInterceptors) {
+		this.responseBodyInterceptors.clear();
+		if (responseBodyInterceptors != null) {
+			this.responseBodyInterceptors.addAll(responseBodyInterceptors);
+		}
+	}
+
 	/**
 	 * Provide resolvers for custom argument types. Custom resolvers are ordered
 	 * after built-in ones. To override the built-in support for argument
@@ -233,6 +249,10 @@ public ApplicationContext getApplicationContext() {
 
 	@Override
 	public void afterPropertiesSet() {
+
+		// Do this first, it may add ResponseBody interceptors
+		initExceptionHandlerAdviceCache();
+
 		if (this.argumentResolvers == null) {
 			List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers();
 			this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
@@ -241,7 +261,30 @@ public void afterPropertiesSet() {
 			List<HandlerMethodReturnValueHandler> handlers = getDefaultReturnValueHandlers();
 			this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);
 		}
-		initExceptionHandlerAdviceCache();
+	}
+
+	private void initExceptionHandlerAdviceCache() {
+		if (getApplicationContext() == null) {
+			return;
+		}
+		if (logger.isDebugEnabled()) {
+			logger.debug("Looking for exception mappings: " + getApplicationContext());
+		}
+
+		List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
+		Collections.sort(beans, new OrderComparator());
+
+		for (ControllerAdviceBean bean : beans) {
+			ExceptionHandlerMethodResolver resolver = new ExceptionHandlerMethodResolver(bean.getBeanType());
+			if (resolver.hasExceptionMappings()) {
+				this.exceptionHandlerAdviceCache.put(bean, resolver);
+				logger.info("Detected @ExceptionHandler methods in " + bean);
+			}
+			if (ResponseBodyInterceptor.class.isAssignableFrom(bean.getBeanType())) {
+				this.responseBodyInterceptors.add(bean);
+				logger.info("Detected ResponseBodyInterceptor implementation in " + bean);
+			}
+		}
 	}
 
 	/**
@@ -274,11 +317,13 @@ protected List<HandlerMethodReturnValueHandler> getDefaultReturnValueHandlers()
 		handlers.add(new ModelAndViewMethodReturnValueHandler());
 		handlers.add(new ModelMethodProcessor());
 		handlers.add(new ViewMethodReturnValueHandler());
-		handlers.add(new HttpEntityMethodProcessor(getMessageConverters(), this.contentNegotiationManager));
+		handlers.add(new HttpEntityMethodProcessor(
+				getMessageConverters(), this.contentNegotiationManager, this.responseBodyInterceptors));
 
 		// Annotation-based return value types
 		handlers.add(new ModelAttributeMethodProcessor(false));
-		handlers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.contentNegotiationManager));
+		handlers.add(new RequestResponseBodyMethodProcessor(
+				getMessageConverters(), this.contentNegotiationManager, this.responseBodyInterceptors));
 
 		// Multi-purpose return value types
 		handlers.add(new ViewNameMethodReturnValueHandler());
@@ -295,26 +340,6 @@ protected List<HandlerMethodReturnValueHandler> getDefaultReturnValueHandlers()
 		return handlers;
 	}
 
-	private void initExceptionHandlerAdviceCache() {
-		if (getApplicationContext() == null) {
-			return;
-		}
-		if (logger.isDebugEnabled()) {
-			logger.debug("Looking for exception mappings: " + getApplicationContext());
-		}
-
-		List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
-		Collections.sort(beans, new OrderComparator());
-
-		for (ControllerAdviceBean bean : beans) {
-			ExceptionHandlerMethodResolver resolver = new ExceptionHandlerMethodResolver(bean.getBeanType());
-			if (resolver.hasExceptionMappings()) {
-				this.exceptionHandlerAdviceCache.put(bean, resolver);
-				logger.info("Detected @ExceptionHandler methods in " + bean);
-			}
-		}
-	}
-
 	/**
 	 * Find an {@code @ExceptionHandler} method and invoke it to handle the raised exception.
 	 */

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/HttpEntityMethodProcessor.java

@@ -57,12 +57,16 @@ public HttpEntityMethodProcessor(List<HttpMessageConverter<?>> messageConverters
 
 	public HttpEntityMethodProcessor(List<HttpMessageConverter<?>> messageConverters,
 			ContentNegotiationManager contentNegotiationManager) {
-
 		super(messageConverters, contentNegotiationManager);
 	}
 
+	public HttpEntityMethodProcessor(List<HttpMessageConverter<?>> messageConverters,
+			ContentNegotiationManager contentNegotiationManager, List<Object> responseBodyInterceptors) {
+		super(messageConverters, contentNegotiationManager, responseBodyInterceptors);
+	}
 
-	@Override
+
+		@Override
 	public boolean supportsParameter(MethodParameter parameter) {
 		return HttpEntity.class.equals(parameter.getParameterType());
 	}

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestMappingHandlerAdapter.java

@@ -132,8 +132,11 @@ public class RequestMappingHandlerAdapter extends AbstractHandlerMethodAdapter
 
 	private List<HttpMessageConverter<?>> messageConverters;
 
+	private List<Object> responseBodyInterceptors = new ArrayList<Object>();
+
 	private WebBindingInitializer webBindingInitializer;
 
+
 	private AsyncTaskExecutor taskExecutor = new SimpleAsyncTaskExecutor("MvcAsync");
 
 	private Long asyncRequestTimeout;
@@ -306,6 +309,14 @@ public List<ModelAndViewResolver> getModelAndViewResolvers() {
 		return modelAndViewResolvers;
 	}
 
+	/**
+	 * Set the {@link ContentNegotiationManager} to use to determine requested media types.
+	 * If not set, the default constructor is used.
+	 */
+	public void setContentNegotiationManager(ContentNegotiationManager contentNegotiationManager) {
+		this.contentNegotiationManager = contentNegotiationManager;
+	}
+
 	/**
 	 * Provide the converters to use in argument resolvers and return value
 	 * handlers that support reading and/or writing to the body of the
@@ -316,18 +327,23 @@ public void setMessageConverters(List<HttpMessageConverter<?>> messageConverters
 	}
 
 	/**
-	 * Set the {@link ContentNegotiationManager} to use to determine requested media types.
-	 * If not set, the default constructor is used.
+	 * Return the configured message body converters.
 	 */
-	public void setContentNegotiationManager(ContentNegotiationManager contentNegotiationManager) {
-		this.contentNegotiationManager = contentNegotiationManager;
+	public List<HttpMessageConverter<?>> getMessageConverters() {
+		return messageConverters;
 	}
 
 	/**
-	 * Return the configured message body converters.
+	 * Add one or more interceptors to be invoked after the execution of a controller
+	 * method annotated with {@code @ResponseBody} or returning {@code ResponseEntity}
+	 * but before the body is written to the response with the selected
+	 * {@code HttpMessageConverter}.
 	 */
-	public List<HttpMessageConverter<?>> getMessageConverters() {
-		return messageConverters;
+	public void setResponseBodyInterceptors(List<ResponseBodyInterceptor> responseBodyInterceptors) {
+		this.responseBodyInterceptors.clear();
+		if (responseBodyInterceptors != null) {
+			this.responseBodyInterceptors.addAll(responseBodyInterceptors);
+		}
 	}
 
 	/**
@@ -481,6 +497,10 @@ protected ConfigurableBeanFactory getBeanFactory() {
 
 	@Override
 	public void afterPropertiesSet() {
+
+		// Do this first, it may add ResponseBody interceptors
+		initControllerAdviceCache();
+
 		if (this.argumentResolvers == null) {
 			List<HandlerMethodArgumentResolver> resolvers = getDefaultArgumentResolvers();
 			this.argumentResolvers = new HandlerMethodArgumentResolverComposite().addResolvers(resolvers);
@@ -493,7 +513,35 @@ public void afterPropertiesSet() {
 			List<HandlerMethodReturnValueHandler> handlers = getDefaultReturnValueHandlers();
 			this.returnValueHandlers = new HandlerMethodReturnValueHandlerComposite().addHandlers(handlers);
 		}
-		initControllerAdviceCache();
+	}
+
+	private void initControllerAdviceCache() {
+		if (getApplicationContext() == null) {
+			return;
+		}
+		if (logger.isInfoEnabled()) {
+			logger.info("Looking for @ControllerAdvice: " + getApplicationContext());
+		}
+
+		List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
+		Collections.sort(beans, new OrderComparator());
+
+		for (ControllerAdviceBean bean : beans) {
+			Set<Method> attrMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), MODEL_ATTRIBUTE_METHODS);
+			if (!attrMethods.isEmpty()) {
+				this.modelAttributeAdviceCache.put(bean, attrMethods);
+				logger.info("Detected @ModelAttribute methods in " + bean);
+			}
+			Set<Method> binderMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), INIT_BINDER_METHODS);
+			if (!binderMethods.isEmpty()) {
+				this.initBinderAdviceCache.put(bean, binderMethods);
+				logger.info("Detected @InitBinder methods in " + bean);
+			}
+			if (ResponseBodyInterceptor.class.isAssignableFrom(bean.getBeanType())) {
+				this.responseBodyInterceptors.add(bean);
+				logger.info("Detected ResponseBodyInterceptor implementation in " + bean);
+			}
+		}
 	}
 
 	/**
@@ -583,7 +631,8 @@ private List<HandlerMethodReturnValueHandler> getDefaultReturnValueHandlers() {
 		handlers.add(new ModelAndViewMethodReturnValueHandler());
 		handlers.add(new ModelMethodProcessor());
 		handlers.add(new ViewMethodReturnValueHandler());
-		handlers.add(new HttpEntityMethodProcessor(getMessageConverters(), this.contentNegotiationManager));
+		handlers.add(new HttpEntityMethodProcessor(
+				getMessageConverters(), this.contentNegotiationManager, this.responseBodyInterceptors));
 		handlers.add(new HttpHeadersReturnValueHandler());
 		handlers.add(new CallableMethodReturnValueHandler());
 		handlers.add(new DeferredResultMethodReturnValueHandler());
@@ -592,7 +641,8 @@ private List<HandlerMethodReturnValueHandler> getDefaultReturnValueHandlers() {
 
 		// Annotation-based return value types
 		handlers.add(new ModelAttributeMethodProcessor(false));
-		handlers.add(new RequestResponseBodyMethodProcessor(getMessageConverters(), this.contentNegotiationManager));
+		handlers.add(new RequestResponseBodyMethodProcessor(
+				getMessageConverters(), this.contentNegotiationManager, this.responseBodyInterceptors));
 
 		// Multi-purpose return value types
 		handlers.add(new ViewNameMethodReturnValueHandler());
@@ -614,31 +664,6 @@ private List<HandlerMethodReturnValueHandler> getDefaultReturnValueHandlers() {
 		return handlers;
 	}
 
-	private void initControllerAdviceCache() {
-		if (getApplicationContext() == null) {
-			return;
-		}
-		if (logger.isDebugEnabled()) {
-			logger.debug("Looking for controller advice: " + getApplicationContext());
-		}
-
-		List<ControllerAdviceBean> beans = ControllerAdviceBean.findAnnotatedBeans(getApplicationContext());
-		Collections.sort(beans, new OrderComparator());
-
-		for (ControllerAdviceBean bean : beans) {
-			Set<Method> attrMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), MODEL_ATTRIBUTE_METHODS);
-			if (!attrMethods.isEmpty()) {
-				this.modelAttributeAdviceCache.put(bean, attrMethods);
-				logger.info("Detected @ModelAttribute methods in " + bean);
-			}
-			Set<Method> binderMethods = HandlerMethodSelector.selectMethods(bean.getBeanType(), INIT_BINDER_METHODS);
-			if (!binderMethods.isEmpty()) {
-				this.initBinderAdviceCache.put(bean, binderMethods);
-				logger.info("Detected @InitBinder methods in " + bean);
-			}
-		}
-	}
-
 	/**
 	 * Always return {@code true} since any method argument and return value
 	 * type will be processed in some way. A method argument not recognized

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/RequestResponseBodyMethodProcessor.java

@@ -69,10 +69,15 @@ public RequestResponseBodyMethodProcessor(List<HttpMessageConverter<?>> messageC
 
 	public RequestResponseBodyMethodProcessor(List<HttpMessageConverter<?>> messageConverters,
 			ContentNegotiationManager contentNegotiationManager) {
-
 		super(messageConverters, contentNegotiationManager);
 	}
 
+	public RequestResponseBodyMethodProcessor(List<HttpMessageConverter<?>> messageConverters,
+			ContentNegotiationManager contentNegotiationManager, List<Object> responseBodyInterceptors) {
+		super(messageConverters, contentNegotiationManager, responseBodyInterceptors);
+	}
+
+
 	@Override
 	public boolean supportsParameter(MethodParameter parameter) {
 		return parameter.hasParameterAnnotation(RequestBody.class);

spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyInterceptor.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright 2002-2014 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.servlet.mvc.method.annotation;
+
+import org.springframework.core.MethodParameter;
+import org.springframework.http.MediaType;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.http.server.ServerHttpRequest;
+import org.springframework.http.server.ServerHttpResponse;
+
+/**
+ * Allows customizing the response after the execution of an {@code @ResponseBody}
+ * or an {@code ResponseEntity} controller method but before the body is written
+ * with an {@code HttpMessageConverter}.
+ *
+ * @author Rossen Stoyanchev
+ * @since 4.1
+ */
+public interface ResponseBodyInterceptor {
+
+	/**
+	 * Invoked after an {@code HttpMessageConverter} is selected and just before
+	 * its write method is invoked.
+	 *
+	 * @param body the body to be written
+	 * @param contentType the selected content type
+	 * @param converterType the selected converter that will write the body
+	 * @param returnType the return type of the controller method
+	 * @param request the current request
+	 * @param response the current response
+	 * @param <T> the type supported by the message converter
+	 *
+	 * @return the body that was passed in or a modified, possibly new instance
+	 */
+	<T> T beforeBodyWrite(T body, MediaType contentType, Class<HttpMessageConverter<T>> converterType,
+			MethodParameter returnType, ServerHttpRequest request, ServerHttpResponse response);
+
+}