SpringMVC Controller解析ajax参数过程详解

<script language="JavaScript">
  function login(){
    var user_name = $("#user_name").val();           //用户名
    var user_password = $("#user_password").val;      //用户密码

    $.ajax({
      url:"<%=path%>/User/Login",
      type:"POST",
      async: false,
      contentType:"application/json;charset=UTF-8",
      dataType:'json',
      data:JSON.stringify({"user_name":user_name,"user_password":user_password}), //将JSON对象转为字符串
      success:function(data){

      }
    });
  }
</script>

<form>
  <div class="form-group">
    <label for="user_name" stype="display:inline;">用户名：</label>
    <input id="user_name" type="text" class="form-control" style="display:inline;" autocomplete="off" />
  </div>
  <div class="form-group">
    <label for="user_password" style="display:inline;">用户密码：</label>
    <input id="user_password" type="text" class="form-control" style="display:inline;" autocomplete="off" />
  </div>
  <div class="col">
    <div class="col-md-4" style="text-align: right;">
      <button type="submit" class="btn btn-success" onclick="login()">登录</button>
    </div>
  </div>
</form>

public class User implements Serializable {
  private Integer user_name;            //用户名
  private String user_password;          //用户密码
  ......
}

@Controller
@RequestMapping("/User")
public class UserController {

  @RequestMapping(value = "/Login",method = {RequestMethod.POST})
  public @ResponseBody Boolean Login(@RequestBody User user) {
    //此时user.getUser_name()就是前端的user_name
    //user.getUser_password()就是前端的user_password
    //根据输入的用户名及用户密码和数据库对比判断是否登录成功，并返回一个布尔值告诉前端
    ······
    return true/false;
  }

public @ResponseBody Boolean Login(@RequestBody User user) {
  System.out.println(user.getUser_name());
  System.out.println(user.getUser_password());
  ······
  return true/false;
}

@RequestMapping(value = "/Login",method = {RequestMethod.POST})
  public @ResponseBody Boolean Login(@RequestBody String body) {
    //此时body是整个请求体的内容
    System.out.println(body);
    //······
  }

@RequestMapping(value = "/Login",method = {RequestMethod.POST})
  public @ResponseBody Boolean Login(@RequestBody Map<String,String> map) {
    //此时map.get("user_name")就是前端的user_name
    System.out.println(map.get("user_name"));
    //map.get("user_password")就是前端的user_password
    System.out.println(map.get("user_password"));
    //map.get("verifycode")就是前端的verifycode
    System.out.println(map.get("verifycode"));
    ······
  }