JPA 工作单元克隆中遇到空或零主键

我了解到JPA并有任务创建数据库并向其中插入一些值。我想知道如何找出最近插入的对象的ID是什么，所以我找到了一种我需要使用的方法flush的方法EntityManager.

不幸的是我得到了

工作单元克隆中遇到空或零主键

当我使用上述方法时出现异常。我认为问题在于我的数据库已经全部ID's设置为自动增量（我使用 ORACLE 11G Express），所以在提交之前null值并回滚事务。

我能做什么来解决它？

This is DB ( ID's are autoincrement[Sequences and Triggers in oracle]):

public class Client {    
    public static void main(String[] args) {
        EntityManagerFactory emf =
                Persistence.createEntityManagerFactory("JpaIntroductionPU");        
        EntityManager em = emf.createEntityManager();
        EntityTransaction et = em.getTransaction();

        et.begin();

        Address ad1 = new Address();
        ad1.setStreet("Skaraktki");
        ad1.setCode("64-340");

        em.persist(ad1);
        em.flush();

        System.out.println(ad1.getAId());
        et.commit();
    }   
}

地址类别

@Entity
@Table(name = "ADDRESS")
@NamedQueries({
    @NamedQuery(name = "Address.findAll", query = "SELECT a FROM Address a"),
    @NamedQuery(name = "Address.findByAId", query = "SELECT a FROM Address a WHERE a.aId = :aId"),
    @NamedQuery(name = "Address.findByStreet", query = "SELECT a FROM Address a WHERE a.street = :street"),
    @NamedQuery(name = "Address.findByCode", query = "SELECT a FROM Address a WHERE a.code = :code")})
public class Address implements Serializable {
    private static final long serialVersionUID = 1L;
    // @Max(value=?)  @Min(value=?)//if you know range of your decimal fields consider using these annotations to enforce field validation
    @Id
    @Basic(optional = false)
    @Column(name = "A_ID")
    private BigDecimal aId;

    @Basic(optional = false)
    @Column(name = "STREET")
    private String street;

    @Basic(optional = false)
    @Column(name = "CODE")
    private String code;

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "aId")
    private Employee employee;

    @OneToOne(cascade = CascadeType.ALL, mappedBy = "aId")
    private Department department;

    public Address() {
    }

    public Address(BigDecimal aId) {
        this.aId = aId;
    }

    public Address(BigDecimal aId, String street, String code) {
        this.aId = aId;
        this.street = street;
        this.code = code;
    }

    public BigDecimal getAId() {
        return aId;
    }

    public void setAId(BigDecimal aId) {
        this.aId = aId;
    }

    public String getStreet() {
        return street;
    }

    public void setStreet(String street) {
        this.street = street;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public Employee getEmployee() {
        return employee;
    }

    public void setEmployee(Employee employee) {
        this.employee = employee;
    }

    public Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }       

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (aId != null ? aId.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Address)) {
            return false;
        }
        Address other = (Address) object;
        if ((this.aId == null && other.aId != null) || (this.aId != null && !this.aId.equals(other.aId))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "jpaintroduction.Address[ aId=" + aId + " ]";
    }

}

这发生在我身上，因为我手动向数据库添加了一个 ID 为 0（零）的条目。 就我而言，EclipseLink“无法”处理 id 为零的情况。 所以我在 persistence.xml 中添加了以下内容：

     <property name="eclipselink.allow-zero-id" value="true"/>

此属性指示 EclipseLink 将零处理为有效 ID。

[1] http://meetrohan.blogspot.de/2011/11/eclipselink-null-primary-key.html