SpringMVC中使用@RequestBody,@ResponseBody注解实现Java对象和XML/JSON数据自动转换（下）

        上一篇分析了Spring中是如何通过使用@ResponseBody注解，实现自动转换Java对象为XML,JSON数据到Reponse中。

        接下来看看如果request中包含了XML或者JSON数据，反过来，如何来通过@RequestBody注解来自动转换为Java对象。

        配合@RequestBody注解，以及HTTP Request Header中的Content-Type属性，HTTP Request Body中包含的XML或者JSON数据可以自动被转换成对应的Java对象。

1).首先在controller中添加handlermapping

/**
 * 根据request header中的Content-Type自动转换XML/JSON->UserDTOX对象
 * 根据request header中的Accept自动选择返回XML or JSON
 */
@ResponseBody
@RequestMapping(value="/createUser", method = RequestMethod.POST)
public UserDTOX createUser(@RequestBody UserDTOX userDTOX) {
	logger.debug("creating a UserDTO:[{}]", userDTOX);
	return new UserDTOX("Hi " + userDTOX.getName(), userDTOX.getAge() + 1);
}

2).运行以下两个测试函数

@Test
public void testJsonRequestResponse() throws IOException, URISyntaxException {
	
	String url = "http://localhost:8080/SpringMVC/createUser";
	HttpHeaders requestHeaders = new HttpHeaders();
	requestHeaders.set("Accept", "application/json");
	requestHeaders.set("Content-Type", "application/json");

	String jsonStr = "{\"name\":\"Jack\",\"age\":16}";

	RestTemplate restTemplate = new RestTemplate();
	HttpEntity<String> httpEntity = new HttpEntity<String>(jsonStr, requestHeaders);
	String jsonData = restTemplate.postForObject(url, httpEntity, String.class);

	System.out.println(jsonData);
}

@Test
public void testXmlRequestResponse() throws IOException, URISyntaxException {
	
	String url = "http://localhost:8080/SpringMVC/createUser";
	HttpHeaders requestHeaders = new HttpHeaders();
	requestHeaders.set("Accept", "application/xml");
	requestHeaders.set("Content-Type", "application/xml");

	String xmlStr = "<userDTOX><name>Jack</name><age>16</age></userDTOX>";

	RestTemplate restTemplate = new RestTemplate();
	HttpEntity<String> httpEntity = new HttpEntity<String>(xmlStr, requestHeaders);
	String xmlData = restTemplate.postForObject(url, httpEntity, String.class);

	System.out.println(xmlData);
}

3).我们甚至可以任意组合请求和应答中的XML/JSON。比如Request=XML，Response=JSON

@Test
public void testXmlRequestJsonResponse() throws IOException, URISyntaxException {
		String url = "http://localhost:8080/SpringMVC/createUser";
		HttpHeaders requestHeaders = new HttpHeaders();
		requestHeaders.set("Accept", "application/json");
		requestHeaders.set("Content-Type", "application/xml");
		
		String xmlStr = "<userDTOX><name>Jack</name><age>16</age></userDTOX>";

		RestTemplate restTemplate = new RestTemplate();
		HttpEntity<String> httpEntity = new HttpEntity<String>(xmlStr, requestHeaders);
		String jsonData = restTemplate.postForObject(url, httpEntity, String.class);

		System.out.println(jsonData);
}

        类似上一篇中的分析，最关键的处理在AbstractMessageConverterMethodArgumentResolver.readWithMessageConverters()。它会根据request header中的Content-Type属性来选择合适的message converter。

        另外，如果不想使用<mvc:annotation-driven/>中默认的RequestMappingHandlerAdapter的话，我们可以在重新定义这个bean，spring会覆盖掉默认的RequestMappingHandlerAdapter。

<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
  <property name="messageConverters">
    <list>
      <bean class="org.springframework.http.converter.ByteArrayHttpMessageConverter"/>
      <bean class="org.springframework.http.converter.StringHttpMessageConverter"/>
      <bean class="org.springframework.http.converter.ResourceHttpMessageConverter"/>
    </list>
  </property>
</bean>

        或者如果只想换messageConverters的话。

<mvc:annotation-driven>
  <mvc:message-converters>
    <bean class="org.example.MyHttpMessageConverter"/>
    <bean class="org.example.MyOtherHttpMessageConverter"/>
  </mvc:message-converters>
</mvc:annotation-driven>

文章来源：http://blog.csdn.net/fw0124/article/details/48312317