@RequestBody, @ResponseBody 注解详解


接上一篇文章讲述处理@RequestMapping的方法参数绑定之后,详细介绍下@RequestBody、@ResponseBody的具体用法和使用时机;同时对曾经看的一篇文章中讲述的某些部分进行澄清 (文章地址:http://www.byywee.com/page/M0/S702/702424.html)。




      i) 该注解用于读取Request请求的body部分数据,使用系统默认配置的HttpMessageConverter进行解析,然后把相应的数据绑定到要返回的对象上;

      ii) 再把HttpMessageConverter返回的对象数据绑定到 controller中方法的参数上。


A) GET、POST方式提时, 根据request header Content-Type的值来判断:

  •     application/x-www-form-urlencoded, 可选(即非必须,因为这种情况的数据@RequestParam, @ModelAttribute也可以处理,当然@RequestBody也能处理);
  •     multipart/form-data, 不能处理(即使用@RequestBody不能处理这种格式的数据);
  •     其他格式, 必须(其他格式包括application/json, application/xml等。这些格式的数据,必须使用@RequestBody来处理);

B) PUT方式提交时, 根据request header Content-Type的值来判断:

  •     application/x-www-form-urlencoded, 必须;
  •     multipart/form-data, 不能处理;
  •     其他格式, 必须;







 * Strategy interface that specifies a converter that can convert from and to HTTP requests and responses.
 * @author Arjen Poutsma
 * @author Juergen Hoeller
 * @since 3.0
public interface HttpMessageConverter<T> {

	 * Indicates whether the given class can be read by this converter.
	 * @param clazz the class to test for readability
	 * @param mediaType the media type to read, can be {@code null} if not specified.
	 * Typically the value of a {@code Content-Type} header.
	 * @return {@code true} if readable; {@code false} otherwise
	boolean canRead(Class<?> clazz, MediaType mediaType);

	 * Indicates whether the given class can be written by this converter.
	 * @param clazz the class to test for writability
	 * @param mediaType the media type to write, can be {@code null} if not specified.
	 * Typically the value of an {@code Accept} header.
	 * @return {@code true} if writable; {@code false} otherwise
	boolean canWrite(Class<?> clazz, MediaType mediaType);

	 * Return the list of {@link MediaType} objects supported by this converter.
	 * @return the list of supported media types
	List<MediaType> getSupportedMediaTypes();

	 * Read an object of the given type form the given input message, and returns it.
	 * @param clazz the type of object to return. This type must have previously been passed to the
	 * {@link #canRead canRead} method of this interface, which must have returned {@code true}.
	 * @param inputMessage the HTTP input message to read from
	 * @return the converted object
	 * @throws IOException in case of I/O errors
	 * @throws HttpMessageNotReadableException in case of conversion errors
	T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
			throws IOException, HttpMessageNotReadableException;

	 * Write an given object to the given output message.
	 * @param t the object to write to the output message. The type of this object must have previously been
	 * passed to the {@link #canWrite canWrite} method of this interface, which must have returned {@code true}.
	 * @param contentType the content type to use when writing. May be {@code null} to indicate that the
	 * default content type of the converter must be used. If not {@code null}, this media type must have
	 * previously been passed to the {@link #canWrite canWrite} method of this interface, which must have
	 * returned {@code true}.
	 * @param outputMessage the message to write to
	 * @throws IOException in case of I/O errors
	 * @throws HttpMessageNotWritableException in case of conversion errors
	void write(T t, MediaType contentType, HttpOutputMessage outputMessage)
			throws IOException, HttpMessageNotWritableException;

该接口定义了四个方法,分别是读取数据时的 canRead(), read() 和 写入数据时的canWrite(), write()方法。

在使用 <mvc:annotation-driven />标签配置时,默认配置了RequestMappingHandlerAdapter(注意是RequestMappingHandlerAdapter不是AnnotationMethodHandlerAdapter,详情查看Spring 3.1 document “16.14 Configuring Spring MVC”章节),并为他配置了一下默认的HttpMessageConverter:

    ByteArrayHttpMessageConverter converts byte arrays.

    StringHttpMessageConverter converts strings.

    ResourceHttpMessageConverter converts to/from org.springframework.core.io.Resource for all media types.

    SourceHttpMessageConverter converts to/from a javax.xml.transform.Source.

    FormHttpMessageConverter converts form data to/from a MultiValueMap<String, String>.

    Jaxb2RootElementHttpMessageConverter converts Java objects to/from XML — added if JAXB2 is present on the classpath.

    MappingJacksonHttpMessageConverter converts to/from JSON — added if Jackson is present on the classpath.

    AtomFeedHttpMessageConverter converts Atom feeds — added if Rome is present on the classpath.

    RssChannelHttpMessageConverter converts RSS feeds — added if Rome is present on the classpath.

ByteArrayHttpMessageConverter: 负责读取二进制格式的数据和写出二进制格式的数据;

StringHttpMessageConverter:   负责读取字符串格式的数据和写出二进制格式的数据;


FormHttpMessageConverter:       负责读取form提交的数据(能读取的数据格式为 application/x-www-form-urlencoded,不能读取multipart/form-data格式数据);负责写入application/x-www-from-urlencoded和multipart/form-data格式的数据;

MappingJacksonHttpMessageConverter:  负责读取和写入json格式的数据;

SouceHttpMessageConverter:                   负责读取和写入 xml 中javax.xml.transform.Source定义的数据;

Jaxb2RootElementHttpMessageConverter:  负责读取和写入xml 标签格式的数据;

AtomFeedHttpMessageConverter:              负责读取和写入Atom格式的数据;

RssChannelHttpMessageConverter:           负责读取和写入RSS格式的数据;



@RequestBody注解时: 根据Request对象header部分的Content-Type类型,逐一匹配合适的HttpMessageConverter来读取数据;

spring 3.1源代码如下:

private Object readWithMessageConverters(MethodParameter methodParam, HttpInputMessage inputMessage, Class paramType)
			throws Exception {

		MediaType contentType = inputMessage.getHeaders().getContentType();
		if (contentType == null) {
			StringBuilder builder = new StringBuilder(ClassUtils.getShortName(methodParam.getParameterType()));
			String paramName = methodParam.getParameterName();
			if (paramName != null) {
				builder.append(' ');
			throw new HttpMediaTypeNotSupportedException(
					"Cannot extract parameter (" + builder.toString() + "): no Content-Type found");

		List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>();
		if (this.messageConverters != null) {
			for (HttpMessageConverter<?> messageConverter : this.messageConverters) {
				if (messageConverter.canRead(paramType, contentType)) {
					if (logger.isDebugEnabled()) {
						logger.debug("Reading [" + paramType.getName() + "] as \"" + contentType
								+"\" using [" + messageConverter + "]");
					return messageConverter.read(paramType, inputMessage);
		throw new HttpMediaTypeNotSupportedException(contentType, allSupportedMediaTypes);

@ResponseBody注解时: 根据Request对象header部分的Accept属性(逗号分隔),逐一按accept中的类型,去遍历找到能处理的HttpMessageConverter;


private void writeWithMessageConverters(Object returnValue,
				HttpInputMessage inputMessage, HttpOutputMessage outputMessage)
				throws IOException, HttpMediaTypeNotAcceptableException {
			List<MediaType> acceptedMediaTypes = inputMessage.getHeaders().getAccept();
			if (acceptedMediaTypes.isEmpty()) {
				acceptedMediaTypes = Collections.singletonList(MediaType.ALL);
			Class<?> returnValueType = returnValue.getClass();
			List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>();
			if (getMessageConverters() != null) {
				for (MediaType acceptedMediaType : acceptedMediaTypes) {
					for (HttpMessageConverter messageConverter : getMessageConverters()) {
						if (messageConverter.canWrite(returnValueType, acceptedMediaType)) {
							messageConverter.write(returnValue, acceptedMediaType, outputMessage);
							if (logger.isDebugEnabled()) {
								MediaType contentType = outputMessage.getHeaders().getContentType();
								if (contentType == null) {
									contentType = acceptedMediaType;
								logger.debug("Written [" + returnValue + "] as \"" + contentType +
										"\" using [" + messageConverter + "]");
							this.responseArgumentUsed = true;
				for (HttpMessageConverter messageConverter : messageConverters) {
			throw new HttpMediaTypeNotAcceptableException(allSupportedMediaTypes);


MappingJacksonHttpMessageConverter 调用了 objectMapper.writeValue(OutputStream stream, Object)方法,使用@ResponseBody注解返回的对象就传入Object参数内。若返回的对象为已经格式化好的json串时,不使用@RequestBody注解,而应该这样处理:
1、response.setContentType("application/json; charset=UTF-8");


1、 Spring 3.1 Doc:


2、Spring 3.x MVC 入门4 -- @ResponseBody & @RequestBody


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