java Hibernate JPA 一对一保存子类实体
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Hibernate JPA one-to-one saving child class entity
提问by PaiS
I have a one-to-one relationship using PrimaryKeyJoinColumnannotated on the parent side. And now I want to save the child entity by itself.
我PrimaryKeyJoinColumn在父端使用注释有一对一的关系。现在我想自己保存子实体。
For example, I have Employeeand EmpInfoas the child entity, I need to save EmpInfo(of course after setting the id property of the parent to it). However, when such an arrangement is used, I get an exception listed below...
例如，我有Employee和EmpInfo作为子实体，我需要保存EmpInfo（当然在将父实体的 id 属性设置为它之后）。但是，当使用这种安排时，我会得到下面列出的例外情况......
org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist
Any ideas why hibernate does not allow this? To be more clear, the code I have is below...
任何想法为什么休眠不允许这样做？更清楚地说，我的代码如下......
ParentEntity:
父实体：
public class Employee {
private Long id;
private String name;
private EmployeeInfo info;
private Integer enumId;
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
public Long getId() {
return id;
}
@Column(name="EMP_NAME")
public String getName() {
return name;
}
@PrimaryKeyJoinColumn
@OneToOne(cascade = CascadeType.REMOVE)
public EmployeeInfo getInfo() {
return info;
}
}
ChildEntity:
子实体：
@Table(name="EMP_INFO")
@Entity
public class EmployeeInfo {
private Long id;
private String email;
@Column(name="EMPLOYEE_EMAIL")
public String getEmail() {
return email;
}
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name = "emp_id", nullable = false)
public Long getId() {
return id;
}
}
The way I try to save it is...
我试图保存它的方法是......
Employee emp = new Employee();
emp.setEnumId(SimpleEnum.COMPLETE);
emp.setName("Shreyas");
EmployeeInfo info = new EmployeeInfo();
info.setEmail("Sh@gmail");
concreteDAO.save(emp); // This uses the JPATemplate provided by Spring JpaDaoSupport
info.setId(emp.getId());
concreteDAO.saveEmpInfo(info);
Any pointers would be much appreciated, as to how can I try to save the child entity?
任何指针将不胜感激，至于我如何尝试保存子实体？
回答by Pascal Thivent
The problem here is that the @Idof EmployeeInfois declared as being auto-generated and you're thus not supposed to set it manually (Hibernate looks at the Entity passed to persistand assumes it is already in the database because the @Idfield is populated).
这里的问题是@IdofEmployeeInfo被声明为自动生成的，因此您不应该手动设置它（Hibernate 查看传递给的实体persist并假设它已经在数据库中，因为该@Id字段已填充）。
In other words, remove the @GeneratedValueon EmployeeInfoif you want to set the PK manually.
换句话说，如果您想手动设置 PK ，请删除@GeneratedValueon EmployeeInfo。
Note that Hibernate provides support for OneToOneassociation using a shared primary key in JPA 1.0 through a custom extension. See:
请注意，HibernateOneToOne通过自定义扩展支持使用 JPA 1.0 中的共享主键进行关联。看：
In JPA 2.0, derived identifiers are well supported and you can annotate OneToOneand ManyToOneassociations with @Id. See:
在JPA 2.0，得到的标识符很好的支持，你可以批注OneToOne和ManyToOne协会有@Id。看：
