绕过GeneratedValue

Question

我正在尝试创建一个服装IdentityGenerator。如果id为null，则生成else赋值。我发现了这个：Bypass GeneratedValue in Hibernate (merge data not in db?)

但我一直得到java.sql.SQLException：字段＆＃39; id＆＃39;没有默认值。

我的实体：

@Entity
public class TestEntity extends AbstractEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY, generator = "IdOrGenerated")
    @GenericGenerator(name = "IdOrGenerated", strategy = "com.xxx.service.UseIdOrGenerate")
    protected Long id;

    @Column(length = 64)
    private String name;


    public TestEntity(String name) {

    super();
    this.name = name;
    }


    public TestEntity(Long id, String name) {

    super();
    this.id = id;
    this.name = name;
    }


    public TestEntity() {

    super();
    }
}

我的自定义生成器：

public class UseIdOrGenerate extends IdentityGenerator {

    @Override
    public Serializable generate(SessionImplementor session, Object object) throws HibernateException {

    Serializable id = session.getEntityPersister(null, object).getClassMetadata().getIdentifier(object, session);

    id = id != null ? id : super.generate(session, object);
    return id;
    }
}

Answer 1

返回未分配的变量/字段会导致错误。需要为字段id分配一个默认值，只要它有一个默认值就无关紧要。

protected Long id = new Long(0);