Hibernate关联关系之一对一关联关系的CRUD操作
说明：本文注释的不是很多，只是功能上能简单的基本达到。要看详细的说明可参考另一篇博文超详细的Hibernate关联关系之双向的一对多关联关系的CRUD操作————学习至黑马程序员****。。当然，one-to-one , many-to-one , many-to-many 这几个标签的属性都各不相同，当用到的时还是需要去查看相关文档的。
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1.项目结构：
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2.pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.lin</groupId>
<artifactId>Hibernate_OneToOne</artifactId>
<version>0.0.1-SNAPSHOT</version>
<dependencies>
<!-- Hibernate -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>3.6.10.Final</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-entitymanager</artifactId>
<version>3.6.10.Final</version>
</dependency>
<!-- MySQL驱动包 -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.41</version>
</dependency>
<!-- slf4j -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-nop</artifactId>
<version>1.7.25</version>
<scope>test</scope>
</dependency>
<!-- jstl、servlet-api、junit -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>jstl</artifactId>
<version>1.2</version>
</dependency>
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
<scope>provided</scope>
</dependency>
<dependency>
<groupId>junit</groupId>
<artifactId>junit-dep</artifactId>
<version>4.10</version>
<scope>test</scope>
</dependency>
</dependencies>
</project>============================
3.实体类跟其对应的映射文件：
User.java
package com.lin.domain;
import java.io.Serializable;
/**
* 用户实体类
* */
public class User implements Serializable{
private static final long serialVersionUID = 1L;
private Long userId;
private String userName;
private String password;
//一个用户只能对应一个身份证，一个身份证只能被一个用户拥有。所以用户和身份证是一对一关联关系。
private Card card;
public User() {
super();
}
public User(Long userId, String userName, String password) {
super();
this.userId = userId;
this.userName = userName;
this.password = password;
}
public Long getUserId() {
return userId;
}
public void setUserId(Long userId) {
this.userId = userId;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Card getCard() {
return card;
}
public void setCard(Card card) {
this.card = card;
}
@Override
public String toString() {
return "User [userId=" + userId + ", userName=" + userName
+ ", password=" + password + "]";
}
}
User.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.lin.domain">
<!-- name指定持久化类的类名，table指定数据表的表名 -->
<class name="User" table="table_user">
<id name="userId" column="user_id">
<generator class="native"/>
</id>
<property name="userName" column="user_name"></property>
<property name="password" column="password"></property>
<!--映射关联属性card。cascade="all"表示级联保存User对象关联的Card对象-->
<one-to-one name="card" class="Card" cascade="all" property-ref="user"></one-to-one>
</class>
</hibernate-mapping>Card.java
package com.lin.domain;
import java.io.Serializable;
/**
* 身份证实体类
* */
public class Card implements Serializable{
private static final long serialVersionUID = 1L;
private Long cardId;
private String cardNumber;
//一个用户只能对应一个身份证，一个身份证只能被一个用户拥有。所以用户和身份证是一对一关联关系。
private User user;
public Card() {
super();
}
public Card(Long cardId, String cardNumber) {
super();
this.cardId = cardId;
this.cardNumber = cardNumber;
}
public Long getCardId() {
return cardId;
}
public void setCardId(Long cardId) {
this.cardId = cardId;
}
public String getCardNumber() {
return cardNumber;
}
public void setCardNumber(String cardNumber) {
this.cardNumber = cardNumber;
}
public User getUser() {
return user;
}
public void setUser(User user) {
this.user = user;
}
@Override
public String toString() {
return "Card [cardId=" + cardId + ", cardNumber=" + cardNumber + "]";
}
}
Card.hbm.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.lin.domain">
<!-- name指定持久化类的类名，table指定数据表的表名 -->
<class name="Card" table="table_card">
<id name="cardId" column="card_id">
<generator class="native"/>
</id>
<property name="cardNumber" column="card_number"></property>
<many-to-one name="user" class="User" unique="true">
<!--column属性指定用来进行关联的外键列列名-->
<column name="user_id"></column>
</many-to-one>
</class>
</hibernate-mapping>============================
4.hibernate.cfg.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<!--
Hibernate配置文件包含了连接持久层与映射文件所需的基本信息。
(Hibernate配置文件主要用来配置数据库连接以及Hibernate运行时所需的各个属性的值。)
-->
<hibernate-configuration>
<session-factory>
<!-- 数据库连接设置 -->
<!-- 配置数据库JDBC驱动 -->
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<!-- 配置数据库连接URL -->
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/hibernate</property>
<!-- 配置数据库用户名 -->
<property name="hibernate.connection.username">root</property>
<!-- 配置数据库密码 -->
<property name="hibernate.connection.password">000000</property>
<!-- 配置JDBC内置连接池 -->
<property name="connection.pool_size">1</property>
<!-- 配置数据库方言 -->
<property name="dialect">org.hibernate.dialect.MySQLDialect</property>
<!-- 配置Hibernate采用何种方式生成DDL语句 -->
<!-- update表示检测实体类的映射配置和数据库的表结构是否一致 -->
<property name="hibernate.hbm2ddl.auto">update</property>
<!-- 输出运行时生成的SQL语句 -->
<property name="show_sql">true</property>
<!-- 列出所有的映射文件 -->
<mapping resource="hibernate/mappings/User.hbm.xml" />
<mapping resource="hibernate/mappings/Card.hbm.xml" />
</session-factory>
</hibernate-configuration>============================
5.hibernate工具类:
HibernateUtil.java
package com.lin.utils;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtil {
private static SessionFactory sessionFactory;
private static Configuration configuration;
//创建线程局部变量threadLocal，用来保存Hibernate的Session
private static final ThreadLocal<Session> threadLocal = new ThreadLocal<Session>();
//使用静态代码块初始化Hibernate
static{
try{
//如果不指定hibernate的配置文件位置，那么它会默认到classpath路径下查找名为hibernate.cfg.xml的文件
Configuration cfg = new Configuration().configure("/hibernate/hibernate.cfg.xml");
//创建SessionFactory
sessionFactory = cfg.buildSessionFactory();
}catch(Throwable ex){
throw new ExceptionInInitializerError(ex);
}
}
//获得SessionFactory
public static SessionFactory getSessionFactory(){
return sessionFactory;
}
//获得ThreadLocal对象管理的Session实例
public static Session getSession() throws HibernateException {
Session session = (Session)threadLocal.get();
if(session == null || session.isOpen()){
if(sessionFactory == null){
rebuildSessionFactory();
}
//通过SessionFactory对象创建Session对象
session = (sessionFactory != null)?sessionFactory.openSession():null;
//将新打开的Session实例保存到线程局部变量threadLocal中
threadLocal.set(session);
}
return session;
}
//关闭Session实例
public static void closeSession() throws HibernateException {
//从线程局部变量threadLocal中获取之前存入的Session实例
Session session = (Session)threadLocal.get();
threadLocal.set(null);
if(session != null){
session.close();
}
}
//重建SessionFactory
public static void rebuildSessionFactory() {
try{
configuration.configure("/hibernate/hibernate.cfg.xml");
sessionFactory = configuration.buildSessionFactory();
}catch(Exception e){
System.out.println("Error Creating SessionFactory ");
e.printStackTrace();
}
}
//关闭缓存和连接池
public static void shutdown(){
getSessionFactory().close();
}
public static void main(String[] args){
HibernateUtil.getSession();
}
}
============================
6.一对一关联关系的CRUD操作：
这边测试的时候有遇到一个问题，就是插入数据的时候，明明在many-to-one 中设置了unique，该外键字段还是可以重复的。难道要在数据库建表的时候设置唯一约束？（我这里的表是通过配置好映射文件后，由Hibernate自动创建表的。。还望大神指教啊，，，）
HibernateOneToOneTest.java
package com.lin.test;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import com.lin.domain.Card;
import com.lin.domain.User;
import com.lin.utils.HibernateUtil;
/**
* 一对一关联映射的CRUD操作。
* */
public class HibernateOneToOneTest {
/**
* 级联保存操作1（保存用户，级联保存身份证）
* 找到User的映射文件，在one-to-one标签上添加属性 cascade="all"即可。
*
* 级联保存操作2（保存身份证，级联保存用户）
* 找到Card的映射文件，在many-to-one标签上添加属性 cascade="save-update"即可。
* */
@Test
public void saveTest1(){
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
User user = new User();
user.setUserName("林6");
user.setPassword("123456");
Card card = new Card();
card.setCardNumber("350111111111111111");
user.setCard(card);
card.setUser(user);
// session.save(user);
session.save(card);
tx.commit();
session.close();
}
/**
* 测试用同一个身份证去关联多个用户
* （这里的测试是能添加进去的，因为many-to-one一方已经加了unique约束，不知道为什么还是添加进去）
* */
@Test
public void saveTest2(){
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
User user = (User) session.get(User.class,1L);
Card card = new Card();
card.setCardNumber("350111111111111111");
card.setUser(user);
session.save(card);
tx.commit();
session.close();
}
/**
* 删除操作
* （我这里测试的要找到User的映射文件中的one-to-one标签设置 property-ref="user"后方可级联删除数据）
* */
@Test
public void deleteTest(){
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
//根据id查询用户
User user = (User) session.get(User.class, 3L);
//删除用户
session.delete(user);
tx.commit();
session.close();
}
/**
* 更新操作
* （仅修改了用户关联的身份的信息）
* */
@Test
public void updateTest(){
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
//根据id查询用户
User user = (User) session.get(User.class, 2L);
//更新用户关联的身份证信息
user.getCard().setCardNumber("350000000000000000");
session.update(user);
tx.commit();
session.close();
}
/**
* 更新操作
* （仅修改了用户的信息）
* */
@Test
public void updateTest2(){
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
//根据id查询用户
User user = (User) session.get(User.class, 2L);
user.setUserName("小杨");
session.update(user);
tx.commit();
session.close();
}
/**
* 查询操作
* （对象导航查询）
* */
@Test
public void selectTest(){
Session session = HibernateUtil.getSession();
Transaction tx = session.beginTransaction();
// String HQL = "from User where userId= ?";
String HQL = "from User where userId = :userId";
// Query query = session.createQuery(HQL).setLong(0, 2L);
// Query query = session.createQuery(HQL).setLong("userId", 2L);
// Query query = session.createQuery(HQL).setParameter(0, 2L);
Query query = session.createQuery(HQL).setParameter("userId", 2L);
//执行完查询后，就发起了两个查询（把关联对象也查出来了）
User user = (User) query.uniqueResult();
System.out.println(user);
System.out.println(user.getCard());
tx.commit();
session.close();
}
}