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Spring boot @ModelAttribute标注

@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")
@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;
}

@ModeAttribute注释方法的参数

@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;
}

原文 https://segmentfault.com/a/1190000021505026

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