var user ={
                         "id" : "1",
                         "username" : "hello",
                         "password" : "123456"
                    };
                    console.log(user);
                    var response = $http.post("/login/signup",user);
                    response.success(function (data) {
                        alert("success");
                        alert(data);
                    });
                    response.error(function (data) {
                        alert("error");
                        alert(data);
                    });

public class User {
    private long userID;
    private String username;
    private String password;

    public User(){

    }

    public User(long userID, String username, String password) {
        this.userID = userID;
        this.username = username;
        this.password = password;
    }


    public long getUserID() {
        return userID;
    }

    public void setUserID(long userID) {
        this.userID = userID;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

@Controller
@RequestMapping(value = "/login")
public class LoginController {

    @RequestMapping(value = "/signup",method = RequestMethod.POST)
    public String signUp(User user){
        String username = user.getUsername();// NULL!!
        System.out.println(username);
        return "login";
    }

}

@RequestMapping(value = "/signup",method = RequestMethod.POST)
    public String signUp(@RequestBody User user){
        String username = user.getUsername();
        System.out.println(username);
        return "login";
    }

The server refused this request because the request entity is in a format not supported by the requested resource for the requested method.