Question

Hibernate OneToMany不会获取所有子实体。有时它会从注释列表中检索所有值，有时则不会。如果我遗漏了一些东西，请帮助我理解。

  @Entity
    @Data
    @Table(name = "Post")
    public class Post implements Serializable {

        @Id
        @GeneratedValue(generator = "UUID")
        @GenericGenerator(name = "UUID", strategy = "org.hibernate.id.UUIDGenerator")
        @Column(name = "id", nullable = false, unique = true)
        private String id;

        @Column(name = "name")
        private String postname;


        @OneToMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER,mappedBy="post",orphanRemoval = true)
        private  List<Comment> comments = new ArrayList<>();

        //getters and setters

    }

@Entity
@Data
@Table(name = "comments")
public class Comment implements Serializable{

    private static final long serialVersionUID = -4522532272183748926L;

    @Id
    @GeneratedValue(generator = "UUID")
    @GenericGenerator(name = "UUID", strategy = "org.hibernate.id.UUIDGenerator")
    @Column(name = "id", nullable = false, unique = true)
    private String id;

    @ManyToOne(fetch = FetchType.EAGER)
    @JoinColumn(name = "comment_id", nullable = false)
    private Post post;

    @Column(name = "sequence", nullable = false)
    private Long sequence;
  //getters and setters

}


 When I fetch , comments list from a post.It is retrieving only one comments entity.Even there are more than one.

有时它会给所有子实体，有时只给一个。

 List<Comment> list = getPost().getComments();
  System.out.println("Size of list : "+getPost().getComments().size()); //giving only 1 comment entity , even there are two entities

        for(int i = 0;i< list.size();i++) {
                            Comment rc = getPost().getComments().get(i);        
                            }

这是从DB获取帖子列表的方法。在数据库中有大约5000个帖子，当一个特定的帖子（一个给一个实体一次，不同运行中的所有实体）的第一个元素这个List，然后检索所有子实体，但是当它位于列表中间的某个位置时，只检索一个子实体。

@Transactional(propagation=Propagation.REQUIRES_NEW)
                public List<Post> getPostList(int firstResult, int maxResult){

                    List<Post> list = null;
                    Session session = sessionFactory.openSession();
                    Criteria criteria = session.createCriteria(Post.class);

                    try {

                        criteria.setFirstResult(firstResult);
                        criteria.setMaxResults(maxResult);
                        criteria.addOrder(Order.asc("dateCreated"));

                        list=Collections.checkedList(criteria.list(), Post.class);

                    }catch(Exception e) {
                            e.printStackTrace();
                    }finally {
                        if(session!=null) {
                            session.close();
                        }
                    }

                    return list;
                }

Hibernate OneToMany FetchType.EAGER有时不会获取所有子实体

0 个答案: