Spring boot @ModelAttribute标注的实现

@RestController
@RequestMapping("/usrcontroller")
public class UserController {

  UserService us = new UserService();

  @ModelAttribute
  public void findUserById(@RequestParam Long uid, Model model) {
    model.addAttribute("user", us.getUser(uid));
  }

  @GetMapping(path="/getuser")
  @ResponseBody
  public String getUser(Model model) {
    User u = (User)(model.getAttribute("user"));
    System.out.println(u.name);
    return u.name;
  }
}

@RestController
@RequestMapping("/groupcontroller")
public class GroupController {
  @ModelAttribute
  public Group getGroupId(@RequestParam Long gid) {
    Group g = new Group();
    g.groupName = "group_"+gid;
    g.groupId = gid;

    return g;
    //same as Model.addAttribute("group", g)
  }

  @GetMapping(path="/getgroup")
  @ResponseBody
  public String getGroup(Model model) {
    Group g = (Group)model.getAttribute("group");
    String gStr = "group(id:" + g.groupId + "," + g.groupName + ")";
    System.out.println(gStr);

    return gStr;
  }
}

//类似于Model.addAttribute("defaultuser", User)
@ModelAttribute("defaultuser")
public User createDefaultUser() {
  return new User("defaultUsr","SH", 22, true);
}

@GetMapping(path="/checkdefaultuser")
@ResponseBody
public String checkDefaultUser(@ModelAttribute("defaultuser") User dfUsr) {
  String dfUsrStr = "Default user("+dfUsr.name + "," + dfUsr.address + "," + dfUsr.age + "," + dfUsr.isMan + ")";

  System.out.println(dfUsrStr);

  return dfUsrStr;
}

@ModelAttribute("defaultuser")
public User createDefaultUser() {
  return new User("defaultUsr","SH", 22, true);
}

@GetMapping(path="/checkdefaultuser")
@ResponseBody
public String checkDefaultUser(@ModelAttribute("defaultuser") User dfUsr) {
  String dfUsrStr = "Default user("+dfUsr.name + "," + dfUsr.address + "," + dfUsr.age + "," + dfUsr.isMan + ")";
  System.out.println(dfUsrStr);
  return dfUsrStr;
}