Spring boot @ModelAttribute标注的实现

@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;
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。