Hibernate实体中的多个SequenceGenerator

Question

在 Hibernate 实体类中使用 2 个序列生成器是否可行？我希望为我的情况使用两个序列生成器，一个用于主键，另一个用于普通字段。如何实现相同的功能？

@Data
@Table(name="a_b")
@SequenceGenerator(name = "a1_seq", sequenceName = "a1_seq", allocationSize    = 1)
@SequenceGenerator(name = "b1_seq", sequenceName = "b1_seq", allocationSize = 1)
public class ABC {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "a1_seq")
    private Integer id;

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

    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "b1")
    @Column(name = "b)
    private Integer b;

}

- Siddharth Agarwal

Answer 1

您的主键应该只有一个SequenceGenerator：

@Id
@Column(name = "id")
@SequenceGenerator(name = "a1_seq", sequenceName = "a1_seq", allocationSize    = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "a1_seq")
private Integer id;

"对于外键，你可以有以下内容："

@Column(name = "b, columnDefinition="serial")
private Integer b;

应该适用于PostgreSQL。

- Vlad Mihalcea

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对我有用...谢谢 :) - Siddharth Agarwal

Oracle怎么样？另外，您如何提供第二个序列的名称？ - Maulik Kayastha

Answer 2

在列级别而不是类级别定义@SequenceGenerator，这样您就可以为两个不同的列创建两个单独的sequenceGenerator-a1_seq和b1。

@Data
@Table(name="a_b")

public class ABC {

  @Id
  @Column(name = "id")
  @SequenceGenerator(name = "a1_seq", sequenceName = "a1_seq", allocationSize    = 1)
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "a1_seq")
  private Integer id;

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

  @SequenceGenerator(name = "b1_seq", sequenceName = "b1_seq", allocationSize = 1)
  @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "b1")
  @Column(name = "b)
  private Integer b;

}

这应该可以工作。虽然我没有测试过，但由于SequenceGenerator在字段级别上是允许的，所以它应该可以工作。

- user1560185

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不是真的！如果你有任何成功的经验，请告诉我们。 - Śhāhēēd

Answer 3

技巧是在序列生成器上添加@Id注解。您可以通过使用@IdClass()来实现此操作。

@Entity
@Table(name = "table_name")
@IdClass(DBSequenceId.class)
public class DBSequence implements Serializable {

    @Id
    @SequenceGenerator(name = "yourName1", sequenceName = "yourSeqName1", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "yourName1")
    @Column(name = "first_seq", updatable = false)
    protected int firstSeq;

    @Id
    @SequenceGenerator(name = "yourName2", sequenceName = "yourSeqName2", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "yourName2")
    @Column(name = "second_seq", updatable = false)
    protected int secondSeq;

}

class DBSequenceId implements Serializable {

    private int firstSeq;
    private int secondSeq;

    //Setters and getters are omitted 
}

已在MariaDB上进行了测试

- Gayath Halanayake