@ModelAttribute可以注释方法和参数

@ModelAttribute注释方法

@ModelAttribute注释方法该方法会在controller的所有方法之前被执行。通过Model将value设定到相应的key中。

(1)注释返回值为void的方法，通过传入Model添加属性值

@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;  }}

(2)注释返回值为具体类型的。通过添加属性（属性名为返回值的头字母小写,例如返回值为Group，属性为group）将返回值添加实际结果类似与model.addAttribute("returnvaluename", var);

@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;  }}

(3)指定属性的名称

//类似于Model.addAttribute("defaultuser", User)@ModelAttribute("defaultuser")public User createDefaultUser() {  return new User("defaultUsr","SH", 22, true);}@GetMapping(path="/checkdefaultuser")@ResponseBodypublic String checkDefaultUser(@ModelAttribute("defaultuser") User dfUsr) {  String dfUsrStr = "Default user("+dfUsr.name + "," + dfUsr.address + "," + dfUsr.age + "," + dfUsr.isMan + ")";  System.out.println(dfUsrStr);  return dfUsrStr;}

@ModeAttribute注释方法的参数

@ModelAttribute("defaultuser")public User createDefaultUser() {  return new User("defaultUsr","SH", 22, true);}@GetMapping(path="/checkdefaultuser")@ResponseBodypublic String checkDefaultUser(@ModelAttribute("defaultuser") User dfUsr) {  String dfUsrStr = "Default user("+dfUsr.name + "," + dfUsr.address + "," + dfUsr.age + "," + dfUsr.isMan + ")";  System.out.println(dfUsrStr);  return dfUsrStr;}