Springmvc 4.x利用@ResponseBody返回Json数据

下面是官方文档对于@ResponseBody注解的解释：

Mapping the response body with the @ResponseBody annotation

The @ResponseBody annotation is similar to @RequestBody. This annotation can be put on a method and indicates that the return type should be written straight to the HTTP response body (and not placed in a Model, or interpreted as a view name). For example:

@RequestMapping(path = "/something", method = RequestMethod.PUT)
@ResponseBody
public String helloWorld() {
return "Hello World";
}
The above example will result in the text Hello World being written to the HTTP response stream.

As with @RequestBody, Spring converts the returned object to a response body by using an HttpMessageConverter. For more information on these converters, see the previous section and Message Converters.

@ResopnseBody注解能够 直接把 控制器返回变量（String）直接 返回给浏览器,也可以通过配置 后，把 对象 序列化成Json数据返回给浏览器！如果为 null 就会返回空白。

怎么配置呢 ？需要配置MessageConverter:

<bean
class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="messageConverters">
<list>
<ref bean="mappingJackson2HttpMessageConverter" />
</list>
</property>
</bean>
<bean id="mappingJackson2HttpMessageConverter"
class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
<property name="supportedMediaTypes">
<list>
<value>text/html;charset=UTF-8</value>
<value>text/json;charset=UTF-8</value>
<value>application/json;charset=UTF-8</value>
</list>
</property>
</bean>

下面贴出在官方文档中的位置：



这个需要jackson jar包支持，需要 jackson-annotations,jackson-core,jackson-databind三个包，：



控制器代码：

@RequestMapping("House/ClassManager/addByAjax")
@ResponseBody
public HanBlog_Class ClassManager_addByAjax(HttpServletRequest request){
if(request.getSession().getAttribute("hanblog_uid")==null) return null;
HanBlog_Class objClass=new HanBlog_Class();
return objClass;
}

jquery代码：

//|增加
$("#hanblog_add_btn").click(function(){
var classname=$("#add_input_name").val();
var classintroduction=$("#add_input_introduction").val();
alert("分类名称:"+classname+"分类介绍:"+classintroduction);
$.get("<c:url value="/House/ClassManager/addByAjax.do" />",function(result){
alert(result);
});
});

运行返回例子：