Hibernate JPA一对一保存子类实体 [英] Hibernate JPA one-to-one saving child class entity

问题描述

我有一对一的关系，使用 PrimaryKeyJoinColumn 在父级注释。例如，我有 Employee 和<$ c ，所以我想自己保存子实体。 $ c> EmpInfo 作为子实体，我需要保存 EmpInfo （当然在设置父项的id属性后）。但是，如果使用这种安排，我会得到下面列出的例外......

  org.springframework.dao.InvalidDataAccessApiUsageException：分离的实体传递给持久
  

为什么hibernate不允许这样做？为了更加清楚，我的代码在下面...

ParentEntity：

  public class Employee {
 private Long id; 
私人字符串名称; 
私人EmployeeInfo信息; 
私人整数enumId; 
 
 @Id 
 @GeneratedValue（strategy = GenerationType.AUTO）
 public Long getId（）{
 return id; 
 
 
 @Column（name =EMP_NAME）
 public String getName（）{
 return name; 
} 
 
 @PrimaryKeyJoinColumn 
 @OneToOne（级联= CascadeType.REMOVE）
公共EmployeeInfo的getInfo（）{
返回信息; 
 
 
  

ChildEntity

  @Table（name =EMP_INFO）
 @Entity 
 public class EmployeeInfo {
 private长ID; 
私人字符串电子邮件; 
 
 @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; 
} 
} 
  

我试图保存它的方式是...

  Employee emp = new Employee（）; 
 emp.setEnumId（SimpleEnum.COMPLETE）; 
 emp.setName（Shreyas）; 
 EmployeeInfo info = new EmployeeInfo（）; 
 info.setEmail（Sh @ gmail）; 
 concreteDAO.save（emp）; //使用Spring JpaDaoSupport提供的JPATemplate 
 
 $ b info.setId（emp.getId（））; 
 concreteDAO.saveEmpInfo（info）; 
  

任何指针都会非常感谢，我该如何尝试保存子实体？ p>

解决方案

这里的问题是 @ code> @Id > EmployeeInfo 被声明为自动生成，因此您不应该手动设置它（Hibernate查看传递给 persist 的实体并且假设它已经在数据库中，因为填充了 @Id 字段）。

换句话说， @GeneratedValue 在 EmployeeInfo 上如果您想手动设置PK。

请注意，Hibernate通过自定义扩展使用JPA 1.0中的共享主键提供对 OneToOne 关联的支持。见：

• JPA Hibernate一对一关系

在JPA 2.0中，衍生标识符得到很好的支持，可以注释 OneToOne 和 ManyToOne 与 @Id 的关联。请参阅：

• 通过OneToOne关系的主键

I have a one-to-one relationship using PrimaryKeyJoinColumn annotated on the parent side. And now I want to save the child entity by itself.

For example, I have Employee and EmpInfo as 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...

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...

ParentEntity:

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:

@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...

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?

解决方案

The problem here is that the @Id of EmployeeInfo is declared as being auto-generated and you're thus not supposed to set it manually (Hibernate looks at the Entity passed to persist and assumes it is already in the database because the @Id field is populated).

In other words, remove the @GeneratedValue on EmployeeInfo if you want to set the PK manually.

Note that Hibernate provides support for OneToOne association using a shared primary key in JPA 1.0 through a custom extension. See:

• JPA Hibernate One-to-One relationship

In JPA 2.0, derived identifiers are well supported and you can annotate OneToOne and ManyToOne associations with @Id. See:

• Primary Keys through OneToOne Relationships

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