@ResponseBody & @RequestBody
@RequestBody inserts the HTTP request body into the method, using the appropriate HttpMessageConverter to write the request body to some object.
@ResponseBody returns the content or object as the HTTP response body, using @ResponseBody will skip the view processing part and instead call the appropriate HttpMessageConverter to write the return value to the output stream.
@ResponseBody can mark any object, and Srping completes the object-protocol conversion
We see that just a few lines of configuration. After using the @ResponseBody annotation, the object returned by the Controller is automatically converted into the corresponding json data, and I have to sigh the power of SpringMVC here.
Yesterday, when @ResponseBody returned JSON format, I always reported http 406 error. I checked the configuration file carefully, and it turned out that there were two configurations. Caused by the failure of the latter one, here is a simple investigation and several solutions
The error roughly means:
HTTP Status 406 (Not Accepted)
->Unable to respond to the requested web page with the requested content attribute.
Many of the online materials say that supportedMediaTypes needs to add application/json;charset=UTF-8, but 406 (Not Acceptable) still appears
One: Make sure applicationContext-configuration.xml is configured with <mvc:annotation-driven>
<mvc:annotation-driven>
<mvc:message-converters>
<bean id="mappingJacksonHttpMessageConverter" class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
<property name="supportedMediaTypes">
<list>
<value>text/plain;charset=utf-8</value>
<value>text/html;charset=UTF-8</value>
<value>text/json;charset=UTF-8</value>
<value>application/json;charset=utf-8</value>
</list>
</property>
<property name="objectMapper">
<bean class="com.fasterxml.jackson.databind.ObjectMapper">
<property name="dateFormat">
<bean class="java.text.SimpleDateFormat">
<constructor-arg type="java.lang.String" value="yyyy-MM-dd HH:mm:ss"/>
</bean>
</property>
</bean>
</property>
</bean>
</mvc:message-converters>
</mvc:annotation-driven>
二:原来springMvc使用@ResponseBody，如果返回的是json结果，需要添加jackson的jar包的依赖
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-core-asl</artifactId>
<version>1.9.13</version>
</dependency>
<dependency>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-mapper-asl</artifactId>
<version>1.9.13</version>
</dependency>
</dependencies>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.8.0</version>
</dependency>
三:测试supportedMediaTypes，就算不配置application/json;charset=UTF-8，也可以正常返回结果。
<property name="supportedMediaTypes">
<list>
<value>text/plain;charset=utf-8</value>
<value>text/html;charset=UTF-8</value>
<value>text/json;charset=UTF-8</value>
<value>application/json;charset=utf-8</value>
</list>
</property>
注意：在使用@ResponseBody 返回json的时候，方法参数中一定不能他添加 PrintWriter printWriter，这就画蛇添足了，而且程序会报错
java.lang.IllegalStateException: getWriter() has already been called for this response
参考：
https://my.oschina.net/lichhao/blog/172562
https://my.oschina.net/HeliosFly/blog/205343
http://www.cnblogs.com/fangjian0423/p/springMVC-xml-json-convert.html