为什么saveandflush后实体中id为null，而数据库中不为null？

Question

我使用最新的 Spring Boot 和 Spring Data JPA 和 Hibernate 。使用的数据库是Oracle 11G。几天来我一直在寻找解决方案，但没有任何效果。我努力 检索数据库中新插入（成功）的实体的 ID。我使用序列和触发器。例如

实体：

    @Entity
    public class Address implements Serializable {
    @Id
    @Column(name = "ID", nullable = false, precision = 0)
    @SequenceGenerator(name = "SEQ_ID_GEN", sequenceName = "GI2S1.SEQ_ID", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "SEQ_ID_GEN")
    private long id;
    private String addressLine;
    private String addressLine2;
    private String city;
    private String postalCode;

    @Id
    public long getId() {
        return id;
    }
    Getters & setters omitted...

触发器：

CREATE OR REPLACE TRIGGER SEQ_ADDRESS_TRIG
    BEFORE INSERT ON ADDRESS
    FOR EACH ROW
BEGIN
    SELECT SEQ_ID.nextval
    INTO :new.id
    FROM dual;
END;
/

顺序：

CREATE SEQUENCE SEQ_ID START WITH 1 INCREMENT BY 1 MINVALUE 1;

查询在控制器中执行。例如

@Controller
@RequestMapping("/address")
public class AddressController {

@Autowired
private AddressRepository addressRepository;

@Transactional
public Address saveAddress(Address address) {
    try {
        return addressRepository.saveAndFlush(address);
    } catch (Exception ex) {
        System.out.println(ex);
    }
    return null;
}

@PostMapping("/create")
public String create(@ModelAttribute Address address) {
    Address saved = saveAddress(address);
    long id = saved.getId();

    System.out.println(saved);

    return (id > 0) ?
            "redirect:/address/find?id=" + id
            :
            "redirect:/address/list";
}

findAll 后的结果 {"id":81,"addressLine":"aa","addressLine2":"a","city":"a","postalCode" :"a"}

但这里是 System.out.println(saved);

之后的对象

Address{id=0, addressLine='aa', addressLine2='a', city='a',
postalCode='a'}

存储库：

@Transactional
public interface AddressRepository extends JpaRepository<Address, Long> {
    List<Address> findByCity(String city);
}

我怀疑会话有问题，数据尚未提交。我对吗？如何解决？谢谢！

Answer 1

问题已解决！

地址实体中gettergetId前有@Id注解

刚刚删除注释

之前：

@Id
public long getId() {
    return id;
}

之后：

public long getId() {
    return id;
}

Answer 2

我遇到了类似的问题。我能够很好地将实体持久保存到数据库中，并且 id 值在数据库中。但是当我通过 REST 接口检索实体时，id 属性为空。我的问题是由于 spring-data-rest 中 HATEOS 支持的副作用，其中 id 不作为属性返回，而是作为 HATEOS 自身返回 link url .要解决此问题，我必须在我的项目中包含以下 class：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.rest.core.config.RepositoryRestConfiguration;
import org.springframework.data.rest.webmvc.config.RepositoryRestConfigurerAdapter;

import javax.persistence.EntityManager;
import javax.persistence.metamodel.Type;

@Configuration
public class RepositoryConfig extends RepositoryRestConfigurerAdapter {
    @Autowired
    private EntityManager entityManager;

    @Override
    public void configureRepositoryRestConfiguration(RepositoryRestConfiguration config) {
        config.exposeIdsFor(
                entityManager.getMetamodel().getEntities().stream()
                        .map(Type::getJavaType)
                        .toArray(Class[]::new));
    }    
}

为什么saveandflush后实体中id为null，而数据库中不为null？

Why is the id null in the entity after saveandflush but not null in the database?

java

oracle

hibernate

id-generation

spring-data-jpa