@RequestBody 和@ResponseBody 注解详解
简介:
@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,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;
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(HTTP消息转化器)
1 * Strategy interface that specifies a converter that can convert from and to HTTP requests and responses. 2 * 3 * @author Arjen Poutsma 4 * @author Juergen Hoeller 5 * @since 3.0 6 */ 7 public interface HttpMessageConverter<T> { 8 9 /** 10 * Indicates whether the given class can be read by this converter. 11 * @param clazz the class to test for readability 12 * @param mediaType the media type to read, can be {@code null} if not specified. 13 * Typically the value of a {@code Content-Type} header. 14 * @return {@code true} if readable; {@code false} otherwise 15 */ 16 boolean canRead(Class<?> clazz, MediaType mediaType); 17 18 /** 19 * Indicates whether the given class can be written by this converter. 20 * @param clazz the class to test for writability 21 * @param mediaType the media type to write, can be {@code null} if not specified. 22 * Typically the value of an {@code Accept} header. 23 * @return {@code true} if writable; {@code false} otherwise 24 */ 25 boolean canWrite(Class<?> clazz, MediaType mediaType); 26 27 /** 28 * Return the list of {@link MediaType} objects supported by this converter. 29 * @return the list of supported media types 30 */ 31 List<MediaType> getSupportedMediaTypes(); 32 33 /** 34 * Read an object of the given type form the given input message, and returns it. 35 * @param clazz the type of object to return. This type must have previously been passed to the 36 * {@link #canRead canRead} method of this interface, which must have returned {@code true}. 37 * @param inputMessage the HTTP input message to read from 38 * @return the converted object 39 * @throws IOException in case of I/O errors 40 * @throws HttpMessageNotReadableException in case of conversion errors 41 */ 42 T read(Class<? extends T> clazz, HttpInputMessage inputMessage) 43 throws IOException, HttpMessageNotReadableException; 44 45 /** 46 * Write an given object to the given output message. 47 * @param t the object to write to the output message. The type of this object must have previously been 48 * passed to the {@link #canWrite canWrite} method of this interface, which must have returned {@code true}. 49 * @param contentType the content type to use when writing. May be {@code null} to indicate that the 50 * default content type of the converter must be used. If not {@code null}, this media type must have 51 * previously been passed to the {@link #canWrite canWrite} method of this interface, which must have 52 * returned {@code true}. 53 * @param outputMessage the message to write to 54 * @throws IOException in case of I/O errors 55 * @throws HttpMessageNotWritableException in case of conversion errors 56 */ 57 void write(T t, MediaType contentType, HttpOutputMessage outputMessage) 58 throws IOException, HttpMessageNotWritableException; 59 60 }
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:
1 ByteArrayHttpMessageConverter converts byte arrays. 2 3 StringHttpMessageConverter converts strings. 4 5 ResourceHttpMessageConverter converts to/from org.springframework.core.io.Resource for all media types. 6 7 SourceHttpMessageConverter converts to/from a javax.xml.transform.Source. 8 9 FormHttpMessageConverter converts form data to/from a MultiValueMap<String, String>. 10 11 Jaxb2RootElementHttpMessageConverter converts Java objects to/from XML — added if JAXB2 is present on the classpath. 12 13 MappingJacksonHttpMessageConverter converts to/from JSON — added if Jackson is present on the classpath. 14 15 AtomFeedHttpMessageConverter converts Atom feeds — added if Rome is present on the classpath. 16 17 RssChannelHttpMessageConverter converts RSS feeds — added if Rome is present on the classpath.
1 ByteArrayHttpMessageConverter: 负责读取二进制格式的数据和写出二进制格式的数据; 2 3 StringHttpMessageConverter: 负责读取字符串格式的数据和写出二进制格式的数据; 4 5 6 ResourceHttpMessageConverter:负责读取资源文件和写出资源文件数据; 7 8 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; 9 10 11 MappingJacksonHttpMessageConverter: 负责读取和写入json格式的数据; 12 13 14 SouceHttpMessageConverter: 负责读取和写入 xml 中javax.xml.transform.Source定义的数据; 15 16 Jaxb2RootElementHttpMessageConverter: 负责读取和写入xml 标签格式的数据; 17 18 19 AtomFeedHttpMessageConverter: 负责读取和写入Atom格式的数据; 20 21 RssChannelHttpMessageConverter: 负责读取和写入RSS格式的数据; 22 23 24 当使用@RequestBody和@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
HttpMessageConverter匹配过程:
@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:
@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;
源代码如下:
1 private void writeWithMessageConverters(Object returnValue, 2 HttpInputMessage inputMessage, HttpOutputMessage outputMessage) 3 throws IOException, HttpMediaTypeNotAcceptableException { 4 List<MediaType> acceptedMediaTypes = inputMessage.getHeaders().getAccept(); 5 if (acceptedMediaTypes.isEmpty()) { 6 acceptedMediaTypes = Collections.singletonList(MediaType.ALL); 7 } 8 MediaType.sortByQualityValue(acceptedMediaTypes); 9 Class<?> returnValueType = returnValue.getClass(); 10 List<MediaType> allSupportedMediaTypes = new ArrayList<MediaType>(); 11 if (getMessageConverters() != null) { 12 for (MediaType acceptedMediaType : acceptedMediaTypes) { 13 for (HttpMessageConverter messageConverter : getMessageConverters()) { 14 if (messageConverter.canWrite(returnValueType, acceptedMediaType)) { 15 messageConverter.write(returnValue, acceptedMediaType, outputMessage); 16 if (logger.isDebugEnabled()) { 17 MediaType contentType = outputMessage.getHeaders().getContentType(); 18 if (contentType == null) { 19 contentType = acceptedMediaType; 20 } 21 logger.debug("Written [" + returnValue + "] as \"" + contentType + 22 "\" using [" + messageConverter + "]"); 23 } 24 this.responseArgumentUsed = true; 25 return; 26 } 27 } 28 } 29 for (HttpMessageConverter messageConverter : messageConverters) { 30 allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes()); 31 } 32 } 33 throw new HttpMediaTypeNotAcceptableException(allSupportedMediaTypes); 34 }
补充:
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");
2、response.getWriter().print(jsonStr);
直接输出到body区,然后的视图为void。
参考资料:
1、 Spring 3.1 Doc:
spring-3.1.0/docs/spring-framework-reference/html/mvc.html
2、Spring 3.x MVC 入门4 -- @ResponseBody & @RequestBody
转载地址:http://www.cnblogs.com/qq78292959/p/3760651.html
ok 上面讲解了实现的过程,简单的可以理解为只要有对应协议的解析器,你就可以通过几行配置,几个注解完成协议——对象的转换工作。
注意:Spring默认的json协议解析由Jackson完成,所以要添加jackson.jar包。
使用@ResponseBody 带来的好处就是由spring 将协议转化为对象,不用我们自己再去转化 同样@RequestBody也是,比如我们在前台传递了参数而controller中使用@RequestBody 则可以直接获得pojo对象,不用我们再去获取参数,组装对象。
下面看看小demo
1、前端代码post提交:
1 function profilep() { 2 // 组装json格式数据 3 var mydata = '{"name":"' + $('#name').val() + '","id":"' 4 + $('#id').val() + '","password":"' + $('#password').val() 5 + '"}'; 6 $.ajaxSetup({ 7 contentType : 'application/json' 8 }); 9 $.post('http://localhost:18080/website2/user/save2.do', mydata, 10 function(data) { 11 alert("id: " + data.id + "\nname: " + data.name 12 + "\password: " + data.password); 13 }, 'json'); 14 }
2、后台代码:
1 @ResponseBody 2 @RequestMapping(value = "/save2.do" ,method = RequestMethod.POST) 3 // 知己接收对象,因@RequestBody spring 帮我们处理了 协议到对象的这个过程 4 public User info2(@RequestBody User user) { 5 String id = user.getId(); 6 String name = user.getName(); 7 String password = user.getPassword(); 8 Map<String, String> map = new HashMap<String, String>(); 9 map.put("id", id); 10 map.put("name", name); 11 map.put("password", password); 12 userService.saveUser(map); 13 User user2= new User(id,name,password); 14 // 直接返回对象,因@ResponseBody spring 会帮我们处理对象和协议之间的转化 15 return user2; 16 }
3、上面两个都是post方法其实get方法也是一样的:
前端代码:
1 function profile() { 2 var url = 'http://localhost:18080/website2/user/save.do?'; 3 var query = 'id=' + $('#id').val() + '&name=' + $('#name').val() 4 + '&password=' + $('#password').val(); 5 url += query; 6 $.get(url, function(data) { 7 alert("id: " + data.id + "\nname: " + data.name + "\nstatus: " 8 + data.password); 9 }); 10 }
后台代码:
1 @ResponseBody 2 @RequestMapping(value = "/save.do" ,method = RequestMethod.GET) 3 public User info(HttpServletRequest request) { 4 String id = request.getParameter("id"); 5 String name = request.getParameter("name"); 6 String password = request.getParameter("password"); 7 Map<String, String> map = new HashMap<String, String>(); 8 map.put("id", id); 9 map.put("name", name); 10 map.put("password", password); 11 userService.saveUser(map); 12 User user= new User(id,name,password); 13 return user; 14 }
上面的$.get方法是使用GET方式进行异步请求。$.post方法使用POST方式来进行异步请求。
$.get 、$.post 方法的格式相同,这里就以$.get为列:
$.get(url [, data] [, callback] [, type])
url:请求的HTML页的URL地址
data(可选):发送至服务器的key/value数据会未为QueryString附加到请求URL中
callback(可选):载入成功时回调函数(即当Response的返回状态为success才调用)自动将请求结果和状态传递给该方法
type(可选):服务器端返回内容的格式,包括xml,html,script,json,text和_default.
这个格式通过上面的post方法和get方法可以看到,像post的那个方法就比较完整!
本文转自:http://www.cnblogs.com/caoyc/p/5644730.html