惠州什么是JPA双向一对一映射？_北大青鸟IT学校

相信大家在学习Java的过程都会遇到各种各样的问题，例如：什么是JPA双向一对一映射？那么下面我们一起来看看惠州北大青鸟学术部老师是怎么讲解这道题的。

以下代码显示了如何进行双向一对一映射。

实例

下面的代码来自Department.java。

package cn.w3cschool.common;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToOne;

@Entitypublic class Department {
 @Id
 @GeneratedValue(strategy=GenerationType.IDENTITY)  private long id;  
 private String name;
 
 @OneToOne(mappedBy="department")  private Person person;  
 public Person getPerson() {
   return person;
 }  public void setPerson(Person person) {
   this.person = person;
 }  public long getId() {
   return id;
 }  public void setId(long id) {
   this.id = id;
 }  public String getName() {
   return name;
 }  public void setName(String name) {
   this.name = name;
 }
}

下面的代码来自Person.java。

package cn.w3cschool.common;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToOne;
@Entitypublic class Person {
 @Id
 @GeneratedValue(strategy=GenerationType.IDENTITY)  private long id;  
 private String name;
 @OneToOne
 @JoinColumn(name="DEPT_ID")
 private Department department;  
 public Person() {}  public Person(String name) {
   this.name = name;
 }  public Department getDepartment() {
   return department;
 }  public void setDepartment(Department department) {
   this.department = department;
 }  public Long getId() {
   return id;
 }  public void setId(Long id) {
   this.id = id;
 }  public String getName() {
   return name;
 }  public void setName(String name) {
   this.name = name;
 }

 @Override  public String toString() {
   return "Person [id=" + id + ", name=" + name + "]";
 }

}

下面的代码来自PersonDaoImpl.java。

package cn.w3cschool.common;


import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.transaction.annotation.Transactional;

@Transactionalpublic class PersonDaoImpl {  public void test(){
   Person p1 = new Person("Tom");
   
   p1.setName("Tom");
   
   Department d = new Department();
   d.setName("Design");
   p1.setDepartment(d);
   d.setPerson(p1);
   
   em.persist(p1);
   em.persist(d);
 }
 @PersistenceContext  private EntityManager em;
}

以下是数据库转储。

Table Name: DEPARTMENT
Row:
   Column Name: ID,
   Column Type: BIGINT:
   Column Value: 1

   Column Name: NAME,
   Column Type: VARCHAR:
   Column Value: Design





Table Name: PERSON
Row:
   Column Name: ID,
   Column Type: BIGINT:
   Column Value: 1

   Column Name: NAME,
   Column Type: VARCHAR:
   Column Value: Tom

   Column Name: DEPT_ID,
   Column Type: BIGINT:
   Column Value: 1

想了解更多关于Java的资讯，可以来惠州北大青鸟新方舟校区了解一下。

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