Question

我使用Spring Boot 1.3.1.RELEASE与Hibernate和H2进行集成测试。以下是我对单向OneToMany关系的兴趣。由于某种原因，生成的外键DDL不包含ON DELETE CASCADE。根据{{3}}，支持参考动作。我尝试了双向OneToMany，但仍然缺少ON DELETE CASCADE。请指教。如果可能的话，我想避免使用Hibernate特定的东西。提前谢谢。

我的实体：

@MappedSuperclass
public abstract class DomainObjectLong implements Persistable<Long> {
    @Id
    @GenericGenerator(name="ID_GEN" , strategy="increment")
    @GeneratedValue(generator = "ID_GEN")
    private Long id;

    @Override
    @Transient
    public boolean isNew() {
        return id == null;
    }
}


@Entity
@Table(name = "event")
public class EventVO extends DomainObjectLong {
    @Column(name = "time", nullable = false, updatable = false)
    private LocalDateTime time = LocalDateTime.now();

    @Column(name = "type", nullable = false, updatable = false)
    @Enumerated(STRING)
    private EventType type;

    @OneToMany(cascade = ALL, fetch = EAGER, orphanRemoval = true)
    @JoinColumn(name = "event_id", nullable = false)
    private List<EventDataVO> data;
}


@Entity
@Table(name = "event_data", uniqueConstraints = {
        @UniqueConstraint(columnNames = {"event_id", "key"})
})
public class EventDataVO extends DomainObjectLong {
    @Column(name = "key", length = 128, nullable = false, updatable = false)
    private String key;

    @Column(name = "value", length = 512, nullable = false, updatable = false)
    private String value;
}

属性：

datasource.runtime.url=jdbc:h2:mem:runtimetestdb;DB_CLOSE_ON_EXIT=FALSE
datasource.runtime.driver-class-name=org.h2.Driver
hibernate.dialect=org.hibernate.dialect.H2Dialect
hibernate.show_sql=true
hibernate.format_sql=true
hibernate.hbm2ddl.auto=create-drop

日志：

23:40:44.648 [localhost-startStop-1] DEBUG org.hibernate.SQL - 
    alter table event_data 
        add constraint FK_6xxhltyiilvlk02730x7mu7cu 
        foreign key (event_id) 
        references event
Hibernate: 
    alter table event_data 
        add constraint FK_6xxhltyiilvlk02730x7mu7cu 
        foreign key (event_id) 
        references event

Answer 1

JPA不会生成ON DELETE CASCADE约束。

原因是在JPA级别上使用toMany或toOne映射映射中的cascade属性完成了级联。

如果数据库将级联删除，则状态将与持久性上下文不匹配，并且JPA将生成删除但数据库记录已被删除。

OneToMany不会在H2数据库上使用ON DELETE CASCADE创建外键

1 个答案: