SpringMVC中@ResponseBody的相关注意点

博主习惯性用SpringMVC的@ResponseBody注解返回JSON字符串，原先采用的方法是GSON将对象转换成json字符串。（需要引入gson-2.x.x.jar的jar包）

	@ResponseBody
	@RequestMapping(value = "/cpuUsage.do", produces = "text/html;charset=UTF-8")
	public String getCpuUsage(@RequestParam(value = "name", required = true) String clusterName)
	{
		logger.info("/charts/cluster/cpuUsage.do?name=" + clusterName);
		String ans = null;
		try
		{
			ans = clusterChartsService.getCpuUsage(clusterName);
			logger.info(ans);
		}
		catch (InstantiationException | IllegalAccessException | RuntimeFaultFaultMsg | DatatypeConfigurationException
				| NullPointerException | ConnectException | XMLStreamException e)
		{
			logger.error(e.getMessage());
		}
		return ans;
	}

	public String getCpuUsage(String clusterName) throws RuntimeFaultFaultMsg, DatatypeConfigurationException,
		InstantiationException, IllegalAccessException, ConnectException, XMLStreamException
	{
		double value = MoniterWsInterface.getClusterCpuUsageByClusterName(clusterName);
		Charts charts = new Charts(value, new Date());
		String ans = Gson.class.newInstance().toJson(charts);
		
		return ans;
	}

但是有些读者可能了解到Spring的@ResponseBody可以自动将对象转换为JSON对象然后返回给前端，这里项目中需要加入两个jar包：jackson-core-asl-1.9.x.jar和jackson-mapper-asl-1.9.x.jar。然后在springMVC的配置文件中加入：

<mvc:annotation-driven />

这句即可，也可以显示的标注，即在springMVC的配置文件中加入：

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

	@RequestMapping("/test.do")
	@ResponseBody
	public List<String> test(){
		List<String> list = new ArrayList<String>();
		list.add("zzh1");
		list.add("zzh1");
		list.add("zzh2");
		list.add("字符串");
		return list;
	}

这里有个小坑。在@ResponseBody注解上面还有一个@RequestMapping注解，有时候需要显示的标注一些信息，如：

@RequestMapping(value = "/test.do", produces = "application/json;charset=UTF-8")

好了@ResponseBody的相关知识先说到这里，以后继续补充。