小编Jas*_*ain的帖子

I have two entities: Comment, and SubComment. A Comment can have multiple SubComments. I'm trying to establish a one to many/many to one bidirectional relationship with Hibernate.

I do not know what is wrong. Both of the tables seem to have been created correctly in PSQL.

Comment.java

import javax.persistence.*;
import java.util.Set;

@Entity
public class Comment {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private long id;

    @Column
    private String text;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "comment")
    private Set<SubComment> subComment;

    public …

我的Comment实体是自加入的，有一个subComment集合。

@Entity
public class Comment {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private String id;

@OneToMany(mappedBy = "parentComment", cascade = CascadeType.ALL)
private Set<Comment> subComments = new HashSet<>();

@ManyToOne
@JoinColumn(referencedColumnName = "id")
private Comment parentComment;

在我的addComment方法中

public ResponseEntity<Comment> addComment(Comment comment) {
    Comment currComment = commentRepository.save(comment);
    if (currComment.getParentId() != null) {
        Comment parent = commentRepository.findById(currComment.getParentId()).orElse(null);
        if (parent != null) {
            parent.addSubComment(currComment);
            currComment.setParentId(parent.getId());
            currComment.setParentComment(parent);
            commentRepository.save(parent);
        }
    }
    Comment responseComment = commentRepository.save(currComment);
    return ResponseEntity.ok(responseComment);
}

当我尝试建立反向关系（拥有方）时， comment.setParentComment(parent);导致错误

comment.setParentComment(parent); 导致错误： …