List 在play framework中将对象添加到列表

我是新手，每当我使用列表时。将（对象）添加到列表并打印列表的大小，它仍然是0

我的方法是喜欢一个教程，它检查登录的用户以前是否喜欢这个教程，如果喜欢，它将教程的likeCount增加1，并将教程添加到用户的like列表中。如果没有，则表示他已经喜欢它。 由于教程没有保存在列表中，我无法检查它是否已经被喜欢了

型号：

    @Entity
    public class RegisteredUser extends Model {
public String name;
    @ManyToMany 
public List<Tutorial> contributedTutorials;

     public RegisteredUser(String name) {
     this.name = name;
     this.likeList = newArrayList<Tutorial>();
     this.save();
     }
     }

    @Entity
    public class Tutorial extends Model {
public  String Title;
    public int likeCount;
    public Tutorial(String title) {
    this.title = title;
    this.likeCount = 0;
    }

观点：

     <a href="@{Tutorials.likeTutorial()}">Like </a>  

+您不需要调用
this.save（）
和
this.likeList=newArrayList（）。实际上，后者在语法上是错误的

+将教程ID作为会话变量传递是非常错误的。您需要将其作为GET参数传递给操作

+将支票替换为：

// to check that this user didn't like this tut before
if (! user.likeList.contains(tut)) {
    // Tutorial.em().createQuery("update Tutorial set likeCount ="+ x +" where id=" +tId).executeUpdate();
    // tut.refresh();
    // user.updateLikeList(tut); // THIS IS NOT WORKING!!!
    tut.likeCount++;
    tut.save();

    // Since it's a ManyToMany relationship, you only need to add it to one list and the other will reflect properly if mappedBy properly
    user.likeList.add(tut); // note that the example you showed uses contributedTutorials not likeList
    user.save();

    renderText("You have successfully liked this Tutorial " + user.likeList.size());
} 

我做了你上面提到的所有调整

及
RegisteredUser模型中的映射

@ManyToMany
public List<Tutorial> likeList;

}
故障部件的代码在哪里，user.updatelkelist（tut）@OHAssan我的意思是我们需要查看user.updateLike的代码，因为这就是fails@PereVillega这里是公共的void更新列表（教程t）{this.likeList.add（t）；this.refresh（）；}
@ManyToMany
public List<Tutorial> likeList;

    @ManyToMany  
    public List<RegisteredUser> likersList;

if (! user.likeList.contains(tut)) {

tut.likeCount++; 
//tut.likersList.add(user); // however this raised an error too! at the next line
tut.save();
//as for the likeCount update, it has worked perfectly, Thank You

// Since it's a ManyToMany relationship, you only need to add it to one list and the other will reflect properly if mappedBy properly 
//I have modified Model Tutorial as shown above and it didn't work too !
user.likeList.add(tut); 
user.save(); // this raised an error!! 

renderText("You have successfully liked this Tutorial " + user.likeList.size());