spring mvc 前后端数据交互笔记（解决415,400问题）

$.ajax({
    url: "/rest/userController/login",
    type: "post",
    data: {"username": "chenhao", "password": "123456"}
});

@RequestMapping("/login")
public String  login(@Valid User user){
   if(userService.login(user)){
        return "index";
   }
   return "login";
}

$.ajax({
    url: "/rest/userController/test",
    type: "post",
    dataType: "json",
    data: {"a":"b"}
});

@RequestMapping("/test")
@ResponseBody
public  Map<String, Object> test( Map<String, Object> user){
    Map<String, Object> map = new HashMap<String, Object>();
    map.put("user", user);
    return map;
}

$.ajax({
    url: "/rest/userController/test",
    type: "post",
    dataType: "json",
    contentType: "application/json",
    data: JSON.stringify({"a":"b"})
});

@RequestMapping("/test")
@ResponseBody
public  Map<String, Object> test(@RequestBody Map<String, Object> user){
    Map<String, Object> map = new HashMap<String, Object>();
    map.put("user", user);
    return map;
}

<!--json数据转换 -->
<bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
    <property value="application/json" name="supportedMediaTypes"/>
</bean>