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

<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 {@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; }
</span>

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;

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;

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:

<span style="font-family:Microsoft YaHei;">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(' ');
builder.append(paramName);
}
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) {
allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes());
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);
}</span>

 

@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:

@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:

<span style="font-family:Microsoft YaHei;">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);
}
MediaType.sortByQualityValue(acceptedMediaTypes);
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;
return;
}
}
}
for (HttpMessageConverter messageConverter : messageConverters) {
allSupportedMediaTypes.addAll(messageConverter.getSupportedMediaTypes());
}
}
throw new HttpMediaTypeNotAcceptableException(allSupportedMediaTypes);
}</span>

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。

@RequestBody, @ResponseBody 注解详解的更多相关文章

  1. @RequestBody, @ResponseBody 注解详解(转)

    原文地址: https://www.cnblogs.com/qq78292959/p/3760651.html @RequestBody, @ResponseBody 注解详解(转) 引言: 接上一篇 ...

  2. @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 ...

  3. 【转】@RequestParam @RequestBody @PathVariable 等参数绑定注解详解

    @RequestParam @RequestBody @PathVariable 等参数绑定注解详解 2014-06-02 11:24 23683人阅读 评论(2) 收藏 举报 目录(?)[+] 引言 ...

  4. @PathVariable @RequestParam @RequestBody等参数绑定注解详解

    一.分类 handler method 参数绑定常用的注解,我们根据他们处理的Request的内容不同分为四类: 处理request uri 部分的注解:   @PathVariable;(这里指ur ...

  5. SpringMVC 常用注解 详解

    SpringMVC 常用注解 详解 SpringMVC 常用注解 1.@RequestMapping                                      路径映射 2.@Requ ...

  6. @ModelAttribute注解详解

    @ModelAttribute注解详解 1.@ModelAttribute定义: 被该注解定义的方法,会在该方法所在的controller的任何目标方法执行之前执行 2.@ModelAttribute ...

  7. Java基础13:反射与注解详解

    Java基础13:反射与注解详解 什么是反射? 反射(Reflection)是Java 程序开发语言的特征之一,它允许运行中的 Java 程序获取自身的信息,并且可以操作类或对象的内部属性. Orac ...

  8. java中的注解详解和自定义注解

    一.java中的注解详解 1.什么是注解 用一个词就可以描述注解,那就是元数据,即一种描述数据的数据.所以,可以说注解就是源代码的元数据.比如,下面这段代码: @Override public Str ...

  9. SpringBoot事务注解详解

    @Transactional spring 事务注解 1.简单开启事务管理 @EnableTransactionManagement // 启注解事务管理,等同于xml配置方式的 <tx:ann ...

随机推荐

  1. Windows Management Instrumentation WMI Security Technology Learning

    目录 . 引言 . WMI(Windows Management Instrumentation)简介 . 基于WMI的攻击向量 . WMI编程示例 0. 引言 在进行服务器主机的入侵检测.安全攻防的 ...

  2. JSTL标签库简介

    核心标签库 http://java.sun.com/jsp/jstl/core <c:catch>,<c:url>的使用 <!-- 捕获异常 --> <c:c ...

  3. ECSHOP验证码背景图修改教程

    ECSHOP验证码背景图修改教程 ECSHOP教程/ ecshop教程网(www.ecshop119.com) 2013-11-18   ECSHOP验证码背景图修改教程: ECSHOP前后台的某些地 ...

  4. 可选择Email和用户名登录的代码

    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/ ...

  5. Linux 安装Rsync和配置

    1.检查rsync 是否已经安装 [root@test home]# rpm -qa|grep rsync 若已经安装,则使用rpm -e 命令卸载. [root@test home]#rpm -e ...

  6. UISearchBar和 UISearchDisplayController的使用

    感觉好多文章不是很全面,所以本文收集整合了网上的几篇文章,感觉有互相补充的效果. 如果想下载源码来看:http://code4app.com/search/searchbar .本源码与本文无关 1. ...

  7. Android-深入理解android自定义属性(AttributeSet,TypedArray)

    属性 自定义属性,首先要定义出来属性,我们新建一个attrs.xml: <?xml version="1.0" encoding="utf-8"?> ...

  8. tar 的一个记录

    今天看到群里有人在问.用tar命令备份/etc/passwd 文件提示删除/的提示 这里我要说明下,tar的打包压缩 命令: tar -zcv -f /backup/passwd.tar.gz /et ...

  9. NBUT1541 Rainwater 题解

    http://cdn.ac.nbutoj.com/Problem/view.xhtml?id=1541 When rain, nocLyt discovered a magical phenomeno ...

  10. 模板插件aTpl

    摘要: 前面给大家分享了一款js模板插件,后来经过完善推荐给大家.该插件支持ie5+,chrome等浏览器以及移动端浏览器,支持for和if语法,以及表达式. 项目地址:https://github. ...