Question

我正在与休眠斗争。我试图删除对象但是我得到了sql异常。

首先是我的映射：

@Entity
public class Meetup {

    @Id
    @GeneratedValue
    @Column
    private long id;

    @Column(nullable = false)
    private ZonedDateTime dateAndTime;

    @ManyToOne(fetch = FetchType.EAGER,cascade=CascadeType.PERSIST)
    private Location location;

////////////////////////

@Entity
public class Location {

    @Id
    @GeneratedValue
    @Column
    private long id;

    @Column(nullable = false)
    private String name;

    @Column(nullable = false)
    private double longitude;

    @Column(nullable = false)
    private double latitude;

    @OneToMany(fetch = FetchType.LAZY, mappedBy = "location")
    private List<Meetup> meetups;

///////////////////////////////////////////

@Entity
public class Match {
    @Id
    @GeneratedValue
    @Column
    private long id;

    @ManyToMany(fetch = FetchType.LAZY, cascade=CascadeType.ALL)
    private List<User> users = new ArrayList<>();

    @OneToOne(cascade=CascadeType.ALL)
    @JoinColumn(name = "meetup_id")
    private Meetup meetup;

所以我试图删除聚会实体，但通过这样做，我不想删除相应的位置实体。现在，当我试图删除聚会实体（entityManager.remove）时，我正在

 constraint ["FKJRLUYUGNHRKYWSVSRE8VE9I9D: PUBLIC.MATCH FOREIGN KEY(MEETUP_ID) REFERENCES PUBLIC.MEETUP(ID) (1)"; SQL statement: delete from meetup where id=? [23503-192]]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement

可以通过将级联类型更改为＆＃34; ALL＆＃34;来解决问题。在meetup类中映射，但显然我的Location实体也将被删除。这是我不想发生的事情。那么如何在不删除位置实体的情况下实现删除聚会实体呢？

Answer 1

您只需要确保在交易边界内按照以下方式处理MeetUp的删除：

// Get your meetup by identifier
final Meetup meetup = entityManager.find( Meetup.class, meetupId );

// cleanup the match associations with meetup
entityManager.createQuery( "FROM Match WHERE meetup = :meetup")
      .setParameter( "meetup", meetup )
      .getResultList()
      .forEach( match -> { match.setMeetup( null ); } );

// remove meetup
entityManager.remove( meetup );

鉴于您的模型，没有必要使用此用例的级联操作来捏造。

删除实体时违反约束

1 个答案: