@RequestBody

发布时间:2016-12-31 7:36:56
来源:分享查询网

@RequestBody

作用: 

      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。

使用时机:

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,[email protected], @ModelAttribute也可以处理,[email protected]);
  •     multipart/form-data, 不能处理([email protected]);
  •     其他格式, 必须(其他格式包括application/json, application/xml等。这些格式的数据,[email protected]);

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;

说明:request的body部分的数据编码格式由header部分的Content-Type指定;

@ResponseBody

作用: 

      该注解用于将Controller的方法返回的对象,通过适当的HttpMessageConverter转换为指定格式后,写入到Response对象的body数据区。

使用时机:

      返回的数据不是html标签的页面,而是其他某种格式的数据时(如json、xml等)使用;

HttpMessageConverter

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<span style="font-family:Microsoft YaHei;">/** * 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 [email protected] null} if not specified.     * Typically the value of a [email protected] Content-Type} header.     * @return [email protected] true} if readable; [email protected] 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 [email protected] null} if not specified.     * Typically the value of an [email protected] Accept} header.     * @return [email protected] true} if writable; [email protected] false} otherwise     */    boolean canWrite(Class<?> clazz, MediaType mediaType);    /**     * Return the list of [email protected] 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     * [email protected] #canRead canRead} method of this interface, which must have returned [email protected] 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 [email protected] #canWrite canWrite} method of this interface, which must have returned [email protected] true}.     * @param contentType the content type to use when writing. May be [email protected] null} to indicate that the     * default content type of the converter must be used. If not [email protected] null}, this media type must have     * previously been passed to the [email protected] #canWrite canWrite} method of this interface, which must have     * returned [email protected] 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;}</span>
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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:

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    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.
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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;

ResourceHttpMessageConverter:负责读取资源文件和写出资源文件数据; 

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;

[email protected]@ResponseBody注解时,RequestMappingHandlerAdapter就使用它们来进行读取或者写入相应格式的数据。


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