1. 导包

2. 直接在代码中加上注解 @ResponseBody  用返回值的方式 直接返回

@Controller
public class JsonController {
    @Resource(name = "userServiceImpl")
    private UserService userService;

    @RequestMapping("responseDemo")
    public @ResponseBody Map responseDemo(@RequestBody QueryVo queryVo){
        System.out.println(queryVo);
        User user = userService.getUserById(10);
        Map<String,Object> map = new HashMap<>();
        map.put("user",user);
        map.put("code",1);
        map.put("msg","查询成功");
        return map;
    }
}

3. 包转换异常

在 springMVC.xml中配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:mvc="http://www.springframework.org/schema/mvc"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd">

        <context:component-scan base-package="cn.hd.controller"></context:component-scan>
        <!--配置json的转换器-->
        <mvc:annotation-driven>
                <mvc:message-converters>
                        <bean class="org.springframework.http.converter.StringHttpMessageConverter"/>
                        <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter"/>
                </mvc:message-converters>
        </mvc:annotation-driven>
</beans>