Question

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我正在将JPA用于此应用程序和Mapping实体的注释。我有一个名为UserStory的实体和另一个名为Revision的实体。 UserStory to Revision有一个OneToMany。

@Entity
@Table(name = "user_story")
@NamedNativeQueries({
    @NamedNativeQuery(name = "storyBacklog", query = "SELECT userstory.rank AS rank, userstory.description AS description, userstory.estimate AS estimate, userstory.name AS name, "
        + "userstory.id AS id, userstory.status AS status FROM user_story userstory ORDER BY userstory.rank ASC", resultClass = UserStory.class),
    @NamedNativeQuery(name = "getCos", query = "SELECT conditions.cos As cos FROM story_cos conditions WHERE conditions.story_id=?1", resultSetMapping = "cosMapping") })
@SqlResultSetMappings({ @SqlResultSetMapping(name = "cosMapping", columns = @ColumnResult(name = "cos")) })
public class UserStory implements Serializable {

  private static final long serialVersionUID = 248298400283358441L;

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;
  ...
  @OneToMany(cascade = CascadeType.ALL)
  @JoinTable(name = "story_revisions", joinColumns = @JoinColumn(name = "story_id"), inverseJoinColumns = @JoinColumn(name = "revision_id"))
  private Set<Revision> revisions;

这是修订实体：

@Entity
@Table(name = "revision")
public class Revision implements Serializable {

  private static final long serialVersionUID = -1823230375873326645L;

  @Id
  @GeneratedValue(strategy = GenerationType.AUTO)
  private Long id;

  @Column(nullable = false)
  private String description;

  @Column(name = "date_created", nullable = false)
  @Temporal(TemporalType.TIMESTAMP)
  private Date creationDate;

当我创建userStory时;我在其上添加了一个修订版，

但是除非我首先坚持故事，否则不会填充连接表然后添加修订并合并它。

这是保存UserStory的代码：

  public UserStory saveUserStory(UserStory userStory) {
    Revision revision = new Revision();
    revision.setCreationDate(new Timestamp(System.currentTimeMillis()));
    revision.setDescription("User story created");
    Set<Revision> revisions = new HashSet<Revision>();
    revisions.add(revision);
    userStory.setRevisions(revisions);
    return storyDao.create(userStory);
  }

在StoryDao中

我调用了persist方法：

@Transactional(readOnly = false)
  public UserStory create(UserStory userStory) {
    if (userStory.getRank() == null) {
      Integer highestRank = 0;
      highestRank = (Integer) entityManager.createNativeQuery("select max(rank) from user_story")
          .getSingleResult();
      if (highestRank != null)
        highestRank += 1;
      else
        highestRank = new Integer(1);
      userStory.setRank(highestRank);
    }
    entityManager.persist(userStory);
    LOGGER.debug("Added User Story with id " + userStory.getId());
    entityManager.detach(userStory);
    return userStory;
  }

这是来自LOGS的SQL

Hibernate: 
    insert 
    into
        user_story
        (description, estimate, name, rank, status) 
    values
        (?, ?, ?, ?, ?)
Hibernate: 
    insert 
    into
        revision
        (date_created, description) 
    values
        (?, ?)
Hibernate: 
    select
        revision0_.id as id5_0_,
        revision0_.date_created as date2_5_0_,
        revision0_.description as descript3_5_0_ 
    from
        revision revision0_ 
    where
        revision0_.id=?
Hibernate: 
    select
        userstory0_.id as id3_1_,
        userstory0_.description as descript2_3_1_,
        userstory0_.estimate as estimate3_1_,
        userstory0_.name as name3_1_,
        userstory0_.rank as rank3_1_,
        userstory0_.status as status3_1_,
        revisions1_.story_id as story1_3_3_,
        revision2_.id as revision2_3_,
        revision2_.id as id5_0_,
        revision2_.date_created as date2_5_0_,
        revision2_.description as descript3_5_0_ 
    from
        user_story userstory0_ 
    left outer join
        story_revisions revisions1_ 
            on userstory0_.id=revisions1_.story_id 
    left outer join
        revision revision2_ 
            on revisions1_.revision_id=revision2_.id 
    where
        userstory0_.id=?

我可以从这里看到它保存用户故事和修订版，但是然后在插入连接表之前尝试运行连接以查看关系是否存在。当然它找不到，因为我正在创建这个对象。

在这种情况下如何填充连接表？

Answer 1

立即行动。这是更新的代码

revisions.add(revision);
userStory = storyDao.create(userStory);
userStory.setRevisions(revisions);
return storyDao.update(userStory);

我仍然不确定为什么要这样做;我坚持一个对象然后更新它的两步法。

JPA：persist不会插入到连接表中

1 个答案: