Question

我正在通过边做边学的方法学习Play框架。我试图制作一个简单的博客（使用官方网站上的信息）并陷入困境。

我试图制作一篇帖子的评论树。到目前为止，我设计的模型类如下：

邮政课程：

@Entity
public class Post extends Model {
@Id
public Long id;

public String title;
public Date postedAt;

@Column(columnDefinition = "TEXT")
public String content;

@OneToMany(cascade=CascadeType.ALL, fetch = FetchType.LAZY, mappedBy="post")
public List<Comment> comments;

public static Finder<Long, Post> find = new Finder(Long.class, Post.class);

public static List<Post> all() {
    return find.all();
}

public static void create(Post post) {
    post.save();
}

public static void delete(Long id) {
    find.ref(id).delete();
}

}

评论类：

@Entity
public class Comment extends Model {
@Id
public Long id;
public String content;

public static Finder<Long, Comment> find = new Finder(Long.class, Comment.class);

public static List<Comment> all() {
    return find.all();
}

public static void create(Comment comment) {
    comment.save();
}

public static void delete(Long id) {
    find.ref(id).delete();
}

@OneToMany(cascade=CascadeType.ALL, fetch = FetchType.LAZY, mappedBy="post")
public List<ChildComment> childComments;

@ManyToOne
public Post post;

}

ChildComment课程：

public class ChildComment extends Model{
@Id
public Long id;
public String content;

@ManyToOne
public Comment comment;

}

控制器类Application.java

public class Application extends Controller {

public static Form<Post> postForm = Form.form(Post.class);

public static Result posts() {

    return ok(views.html.index.render(Post.all(), postForm));
}

public static Result index() {

    return redirect(routes.Application.posts());
}

public static Result newPost() {

    Form<Post> filledForm = postForm.bindFromRequest();
    if (filledForm.hasErrors()) {

        return badRequest(views.html.index.render(Post.all(), filledForm));
    } else {

        Post.create(filledForm.get());
        return redirect(routes.Application.posts());
    }
}

public static Result deletePost(Long id) {

    Post.delete(id);
    return redirect(routes.Application.posts());
}

}

我知道我必须使用一对多关系来完成任务（在模型类中，我认为我做得正确）但是我被困在实施中控制器中的逻辑来管理注释的注释和注释。任何线索或建议都会很棒。

P.S。我正在使用MySql数据库

Answer 1

要创建评论，您可以这样做。

在控制器中传递帖子ID和评论数据

然后在Controller

中

//post_id and commentData received from view
Post post=Post.findByPostId(post_id);                 //find post of that comment where findByPostId() is a function in model
Comment comment=new Comment(commentData,null,post);   //Create a new Comment Object
Comment cm=Comment.save(comment);                     //where save() saves the Comment object in data base and return the saved object
List <Comments> allCommentsOnPost=post.getComments(); //get all comments on that post
allComments.add(cm);                                  //add new comment to list
post.setComments(allCommentsOnPost);                  //set the new list in Post object
post.update(post_id);                                 //update post entity

与保存子注释类似，从视图传递comment_id，childCommentData

//comment_id and childCommentData received from view
Comment cm=Comment.findByCommentId(comment_id);                //find comment from id ,findByCommentId() defined in Comment entity

ChildComment childCom=new ChildComment(childCommentData,cm);    //create new object of ChildComment
ChildComment childComment=ChildComment.save(childCom);                                       //persist the child comment object in db ,save() is a function in model which saves ChildComment object and return it

List<ChildComments> allChildComments=cm.getChildComments();     //getting list of all the ChildComments .
allChildComments.add(childComment);                             //add new comment to list

cm.setChildComments(allChildComments);                          //set all the child comments in Comment Entity

cm.update(comment_id);                                          //update the Comments entity in db

注意：我在两种情况下都在创建新的Comment和ChildComment对象你也可以使用bindRequest（）。get（）来获取Entity对象

Answer 2

实际上，您不需要为儿童使用两个课程 - 这样您只需要两个级别的评论，而只需向Comment模型添加字段：

@ManyToOne
public Comment parent;

@OneToMany(cascade=CascadeType.ALL, fetch = FetchType.LAZY, mappedBy="parent")
public List<Comment> children;

这样你就可以在理论上拥有无限的树枝。

在创建新评论期间，您可以添加父评论的ID - 如果它为空，则表示评论位于根级别（没有父母）

使用ebean ORM和java在Play Framework 2.3.8中创建一个注释树

2 个答案: