Java 用JPA映射弱实体

我的数据库包含一个公司和员工的数据库。我把员工塑造成公司的弱势实体

我的JPA注释如下所示：

@Entity
public class Company extends Model {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    public Long id;

    @OneToMany(mappedBy = "company", cascade = CascadeType.ALL)
    private List<Employee> employees;

}

将创建以下SQL代码：

create table employee (
  id                            bigint auto_increment not null,
  company_id                    bigint not null,
  constraint pk_employee primary key (id)
);

alter table employee add constraint fk_employee_company_id foreign key (company_id) references company (id) on delete restrict on update restrict;

我想要的是（约束pk_员工主键（id，公司id）：

有没有办法创建这样的SQL脚本

编辑： 让

Employee

实现

Serializable

并不奏效

Caused by: javax.persistence.PersistenceException: Could not find BeanDescriptor for class models.Company. Perhaps the EmbeddedId class is not registered?
    at io.ebeaninternal.server.deploy.BeanEmbeddedMetaFactory.create(BeanEmbeddedMetaFactory.java:26)
    at io.ebeaninternal.server.deploy.BeanPropertyAssocOne.<init>(BeanPropertyAssocOne.java:79)
    at io.ebeaninternal.server.deploy.BeanPropertyAssocOne.<init>(BeanPropertyAssocOne.java:62)
    at io.ebeaninternal.server.deploy.meta.DeployBeanTable.createProperty(DeployBeanTable.java:68)
    at io.ebeaninternal.server.deploy.meta.DeployBeanTable.createIdProperties(DeployBeanTable.java:59)
    at io.ebeaninternal.server.deploy.BeanTable.<init>(BeanTable.java:42)

原因：javax.persistence.PersistenceException:找不到类models.Company的BeanDescriptor。可能EmbeddedId类未注册？
在io.ebeaninternal.server.deploy.BeanEmbeddedMetaFactory.create（BeanEmbeddedMetaFactory.java:26）
位于io.ebeaninternal.server.deploy.BeanPropertySsocone。（BeanPropertySsocone.java:79）
位于io.ebeaninternal.server.deploy.BeanPropertySsocone。（BeanPropertySsocone.java:62）
位于io.ebeanternal.server.deploy.meta.DeployBeanTable.createProperty（DeployBeanTable.java:68）
位于io.ebeaninternal.server.deploy.meta.DeployBeanTable.createIdProperties（DeployBeanTable.java:59）
位于io.ebeaninternal.server.deploy.BeanTable。（BeanTable.java:42）

只需在您的

@JoinColumn

注释下添加

@Id

注释。但是

员工

类必须

实现可序列化

才能使用此解决方案。

感谢@Alan Hay为我们提供了链接

下面是如何创建一个弱实体地址，该地址从表pmo_user中获取其Id（user_Id）

pmo_user{id, ....}
test_address{user_id, address}

============================

@Entity
@Table(name="test_address")
public class Address 
{
    @Id
    @Column(name="user_id")
    protected int userId;

    @OneToOne
    @PrimaryKeyJoinColumn(name="user_id", referencedColumnName="id")
    protected PmoUser owner;

    @Column(name="address")
    protected String address;


    public void setOwner(PmoUser owner) 
    {
        this.owner = owner;
        this.userId = owner.getId();
    }


    @Override
    public String toString() {
        return "Address [userId=" + userId + ", owner=" + owner + ", address=" + address + "]";
    }    

}

---

你为什么需要这个？弱实体是什么意思？你要找的是员工的复合PK。这是相当标准的，选项如下：@Alan Hay如果你将此添加为解决方案，我可以接受。谢谢。它成功了。不幸的是，它不起作用。我添加了错误消息。

pmo_user{id, ....}
test_address{user_id, address}

@Entity
@Table(name="test_address")
public class Address 
{
    @Id
    @Column(name="user_id")
    protected int userId;

    @OneToOne
    @PrimaryKeyJoinColumn(name="user_id", referencedColumnName="id")
    protected PmoUser owner;

    @Column(name="address")
    protected String address;


    public void setOwner(PmoUser owner) 
    {
        this.owner = owner;
        this.userId = owner.getId();
    }


    @Override
    public String toString() {
        return "Address [userId=" + userId + ", owner=" + owner + ", address=" + address + "]";
    }    

}