为什么外键没有插入到休眠状态 [英] Why Foreign key not inserted in hibernate

问题描述

我有两个实体。员工和地址。这些实体之间的关系是@OneToOne。当我想插入到外键不插入到表中。
我的实体是：

$ p $ @Entity
@Table（name =Address）
公共类地址{

@Id
@Column（name =Id）
private int Id;
$ b $ @ @OneToOne（fetch = FetchType.LAZY）
@JoinColumn（name =emp_id，
insertable = true，updatable = false，
nullable = true）
私人雇员雇员;


和员工实体

  @Entity 
 @Table（name =EMPLOYEE）
 public class Employee {
 
 @Id 
 @GeneratedValue 
 @ Column（name =emp_id）
 private int emp_id; 
 
 $ b $ @ @OneToOne（fetch = FetchType.EAGER，cascade = CascadeType.ALL）
 @JoinColumn（name =emp_id，
 insertable = true，updatable = false，
 nullable = true）
私有地址; 
  

和添加员工的代码

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

数据库表中的外键是否已指定？

解决方案

您只需在关系所属的一方 @JoinColumn 。因此，如果在数据库中有外键 Address 表，列 emp_id 到 Employee 表，列 id ，映射应该是这样的

地址

  @Entity 
 @Table（name =Address）
 public class Address { 
 
 
 
 @OneToOne（fetch = FetchType.LAZY）
 @JoinColumn（name =emp_id，
 insertable = true，可更新= false，
 nullable = true）
私人员工雇员; 
  

员工

  @Entity 
 @Table（name =EMPLOYEE）
 public class Employee {
 
 ... 
 
 @OneToOne（fetch = FetchType.EAGER，cascade = CascadeType.ALL，mappedBy =employee）
私有地址; 
  

i have two entities. Employee and address. relation between this entities is @OneToOne. when i want to insert into db the foreign key not be insert into table. my entity are:

  @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 ;  

and employee entity

 @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; 

and code for add employee

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

Should foreign keys in database tables is specified ?

解决方案

You only need @JoinColumn on the owning side of a relationship. So, if in database you have foreign key from Address table, column emp_id to Employee table, column id, the mapping should look like this

Address

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

    ...

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

Employee

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

    ...

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

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