SpringBoot 亲子关系

Question

我有以下 Springboot 代码：

comment.java

@Entity
@Getter @Setter @NoArgsConstructor @RequiredArgsConstructor
public class Comment extends Auditable {

    @Id
    @GeneratedValue
    private Long id;

    @NonNull
    private String comment;

    @ManyToOne(fetch = FetchType.LAZY)
    private Link link;
}

链接.java

@Entity
@Getter @Setter @NoArgsConstructor @RequiredArgsConstructor
public class Link extends Auditable {

    @Id
    @GeneratedValue
    private Long id;

    @NonNull
    private String title;

    @NonNull
    private String url;

    @OneToMany(cascade = CascadeType.ALL, mappedBy = "link")
    private List<Comment> comments = new ArrayList<>();

    public void addComment(Comment c) {
        comments.add(c);
    }
}

还有下面的Runner：

 @Bean
 CommandLineRunner someRunner(LinkRepository lr, CommentRepository cr) {
     return args -> {
         Link link = new Link("Getting started", "url");
         Comment c = new Comment("Hello!");
         link.addComment(c);
         linkRepository.save(link);
     };
 };

我正在尝试将评论链接到链接，并将两者保存在一起。然而，这是输出：

[
    {
        createdBy: null,
        createdDate: "2/28/19, 11:48 PM",
        lastModifiedBy: null,
        lastModifiedDate: "2/28/19, 11:48 PM",
        id: 2,
        comment: "Hello!",
        link: null
    }
]

关于如何让链接实际显示在链接列表中的任何建议？

Answer 1

在双向关系中，必须设置关系的双方；

Link link = new Link("Getting started", "url");
Comment comment = new Comment("Hello!");
comment.setLink(link);  // missing in your code
link.addComment(comment);
linkRepository.save(link);

勾选“双向多对一关联” > here