Question

我可以为一个实体使用多个序列生成器，例如

@Id
@SequenceGenerator(name=”subscription_id_seq”,sequenceName=”subscription_id_seq”, allocationSize=7)
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator=”subscription_id_seq”)
@Column(unique=true, nullable=false)
private Integer id

@Column(name="code", nullable=false, unique=true )
@SequenceGenerator(name="subscription_code_1_seq",sequenceName="subscription_code_1_seq", allocationSize=7)
@GeneratedValue(strategy=GenerationType.SEQUENCE, generator="subscription_code_1_seq")
private Integer code;

Answer 1

不，你不能。生成器仅适用于标识符列。

确保使用脚本创建此序列（例如hibernate.hbm2ddl.import_files）：

create sequence subscription_code_1_seq start 1 increment 7

然后使用这样的映射：

@Id
@SequenceGenerator(
        name="subscription_id_seq",
        sequenceName="subscription_id_seq",
        allocationSize=7
)
@GeneratedValue(
        strategy=GenerationType.SEQUENCE,
        generator="subscription_id_seq"
)
@Column(unique=true, nullable=false)
private Integer id;

@Column(
        name="code",
        nullable=false,
        unique=true,
        insertable = false,
        updatable = false,
        columnDefinition = "BIGINT DEFAULT nextval('subscription_code_1_seq')"
)
@Generated(GenerationTime.INSERT)
private Integer code;

Answer 2

简而言之，您可以为一个实体使用多个序列生成器，但仅用于主键（复合主键）。

来自SequenceGenerator文档：

定义在为GeneratedValue批注指定生成元素时可以通过名称引用的主键生成器。可以在实体类或主键字段或属性上指定序列生成器。生成器名称的范围对于持久性单元是全局的（跨所有生成器类型）。

代码示例：

public class TestPK implements Serializable {

    private Integer test1;

    private Integer test2;

    ...
}

@Entity
@IdClass(TestPK.class)
public class Test implements Serializable {

    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name = "seq_test1", sequenceName = "seq_test1", allocationSize = 7)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "seq_test1")
    @Column(name = "test1", unique = true, nullable = false)
    private Integer test1;

    @Id
    @Column(name = "test2", nullable = false, unique = true)
    @SequenceGenerator(name = "seq_test2", sequenceName = "seq_test2", allocationSize = 7)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "seq_test2")
    private Integer test2;

    ...

    @Override
    public String toString() {
        return "Test{" +
                "test1=" + test1 +
                ", test2=" + test2 +
                '}';
    }
}

public interface TestRepository extends Repository<Test, String> {

    Page<Test> findAll(Pageable pageable);

    void save(Test test);
}

@SpringBootApplication
public class Application implements CommandLineRunner {

    @Autowired
    private TestRepository testRepository;

    @Override
    public void run(String... args) throws Exception {
        testRepository.save(new Test());
        Page<Test> all = testRepository.findAll(null);
        System.out.println(all.iterator().next());
    }

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

具有PostgreSQL的一个实体的多个Hibernate序列生成器

2 个答案: