為什么沒有在休眠中插入外鍵

Question

我有兩個實體。 員工和地址。 這些實體之間的關系是@OneToOne。 當我想插入數據庫的外鍵不插入表。 我的實體是：

  @Entity
  @Table(name="Address")
  public class Address{

  @Id
  @Column(name="Id")
  private int Id;

 @OneToOne(fetch=FetchType.LAZY)
 @JoinColumn(name="emp_id", 
        insertable=true, updatable=false, 
        nullable=true)
 private Employee  employee ;  

和員工實體

 @Entity
 @Table(name="EMPLOYEE")
 public class Employee{

@Id 
@GeneratedValue
@Column(name="emp_id")
private int emp_id;


@OneToOne(fetch =FetchType.EAGER, cascade = CascadeType.ALL)
@JoinColumn(name="emp_id", 
       insertable=true, updatable=false, 
       nullable=true)
private Address address; 

和添加員工的代碼

Employee employee = new Employee("john" , ... );
Address address = new Address("USA" , ...);
employee.setAddress(address);
address.setEmployee(employee);
employeeService.addEmployee(employee);

是否應該在數據庫表中指定外鍵？

Answer 1

您只需要關系擁有方的@JoinColumn 。 因此，如果在數據庫中有從Address表的第emp_id列到Employee表的第id列的外鍵，則映射應如下所示

地址

@Entity
@Table(name="Address")
public class Address {

    ...

   @OneToOne(fetch=FetchType.LAZY)
   @JoinColumn(name="emp_id", 
        insertable=true, updatable=false, 
        nullable=true)
   private Employee  employee ;  

雇員

@Entity
@Table(name="EMPLOYEE")
public class Employee{

    ...

    @OneToOne(fetch =FetchType.EAGER, cascade = CascadeType.ALL, mappedBy = "employee")
    private Address address;