先配置 XXX_ servletxml 
<!-- 整合jackson 返回一个json格式 -->
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
<property name="messageConverters">
<list>
<ref bean="mappingJacksonHttpMessageConverter"/>
</list>
</property>
</bean>
<bean id="mappingJacksonHttpMessageConverter" class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter"/>

再然后Action方法里注解就可以
@RequestMapping(value="/XXXXXX", method = RequestMethod.POST)
@ResponseBody
public 返回类型 XXXXXX(){

}