[原创]java WEB学习笔记85：Hibernate学习之路-- -映射 一对一关系 ，基于主键方式实现

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1.基于主键映射的 1-1　　

　　1）基于主键的映射策略:指一端的主键生成器使用 foreign 策略,表明根据”对方”的主键来生成自己的主键，自己并不能独立生成主键. <param> 子元素指定使用当前持久化类的哪个属性作为 “对方”

　　　　

 <hibernate-mapping package="com.jason.hibernate.entities.primary.one2one">

     <class name="Department" table="DEPARTMENT">

         <id name="deptId" type="java.lang.Integer">
             <column name="DEPT_ID" />
             <generator class="foreign">
 8                 <param name="property">mgr</param>
 9             </generator>
         </id>

         <property name="deptName" type="java.lang.String">
             <column name="DEPT_NAME" />
         </property>

         <one-to-one name="mgr" class="Manager" constrained="true"></one-to-one>

     </class>

 </hibernate-mapping>

　　

　　2）采用foreign主键生成器策略的一端增加 one-to-one 元素映射关联属性，其one-to-one属性还应增加 constrained=“true” 属性；另一端增加one-to-one元素映射关联属性。

　　

 <hibernate-mapping package="com.jason.hibernate.entities.primary.one2one">
     <class name="Manager" table="MANAGER">

         <id name="mgrId" type="java.lang.Integer">
             <column name="MGR_ID" />
             <generator class="native" />
         </id>

         <property name="mgrName" type="java.lang.String">
             <column name="MGR_NAME" />
         </property>

         <one-to-one name="dept" class="Department"></one-to-one>

     </class>

 </hibernate-mapping>

　　3）constrained(约束):指定为当前持久化类对应的数据库表的主键添加一个外键约束，引用被关联的对象(“对方”)所对应的数据库表主键

2.代码

Department

 package com.jason.hibernate.entities.foreign.one2one;

 public class Department {
     private Integer deptId;
     private String deptName;

     private Manager mgr;

     public Integer getDeptId() {
         return deptId;
     }

     public void setDeptId(Integer deptId) {
         this.deptId = deptId;
     }

     public String getDeptName() {
         return deptName;
     }

     public void setDeptName(String deptName) {
         this.deptName = deptName;
     }

     public Manager getMgr() {
         return mgr;
     }

     public void setMgr(Manager mgr) {
         this.mgr = mgr;
     }

 }

Manager

 package com.jason.hibernate.entities.foreign.one2one;

 public class Manager {

     private Integer mgrId;
     private String mgrName;
     private Department dept;

     public Integer getMgrId() {
         return mgrId;
     }

     public void setMgrId(Integer mgrId) {
         this.mgrId = mgrId;
     }

     public String getMgrName() {
         return mgrName;
     }

     public void setMgrName(String mgrName) {
         this.mgrName = mgrName;
     }

     public Department getDept() {
         return dept;
     }

     public void setDept(Department dept) {
         this.dept = dept;
     }

 }

Department.hbm.xml

 <?xml version="1.0"?>
 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 <!-- Generated 2016-10-5 22:31:35 by Hibernate Tools 3.4.0.CR1 -->
 <hibernate-mapping package="com.jason.hibernate.entities.primary.one2one">

     <class name="Department" table="DEPARTMENT">

         <id name="deptId" type="java.lang.Integer">
             <column name="DEPT_ID" />
             <generator class="foreign">
                 <param name="property">mgr</param>
             </generator>
         </id>

         <property name="deptName" type="java.lang.String">
             <column name="DEPT_NAME" />
         </property>

         <one-to-one name="mgr" class="Manager" constrained="true"></one-to-one>

     </class>

 </hibernate-mapping>

Manager.hbm.xml

 <?xml version="1.0"?>
 <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 <!-- Generated 2016-10-5 22:31:35 by Hibernate Tools 3.4.0.CR1 -->
 <hibernate-mapping package="com.jason.hibernate.entities.primary.one2one">
     <class name="Manager" table="MANAGER">

         <id name="mgrId" type="java.lang.Integer">
             <column name="MGR_ID" />
             <generator class="native" />
         </id>

         <property name="mgrName" type="java.lang.String">
             <column name="MGR_NAME" />
         </property>

         <one-to-one name="dept" class="Department"></one-to-one>

     </class>

 </hibernate-mapping>

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-configuration>
     <session-factory>
         <!-- hibernate 连接数据库的基本信息 -->
         <property name="connection.username">root</property>
         <property name="connection.password">zhangzhen</property>
         <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
         <property name="connection.url">jdbc:mysql:///hibernate</property>

         <!-- 配置hibernate 的节本信息 -->
         <!-- hibernate 所使用的数据库方言 -->
         <!--<property name="dialect">org.hibernate.dialect.MySQLInnoDBDialect</property>-->
    <property name="dialect">org.hibernate.dialect.MySQLDialect</property>
         <!-- 执行操作时是否在控制台打印SQL  -->
         <property name="show_sql">true</property>

         <!-- 是否都SQL 进行格式化 -->
         <property name="format_sql">true</property>

         <!-- 指定自动生成数据表的策略 -->
         <property name="hbm2ddl.auto">update</property>

         <!-- 设置hibernate 的事务隔离级别 -->
         <property name="connection.isolation">2</property>

         <!-- 配置c3p0 -->
         <property name="hibernate.c3p0.max_size">10</property>
         <property name="hibernate.c3p0.min_size">5</property>
         <property name="c3p0.acquire_increment">2</property>
         <property name="c3p0.idle_test_period">2000</property>
         <property name="c3p0.timeout">2000</property>
         <property name="c3p0.max_statements">10</property>

         <!-- 对于mysql 无效，对于oracle 有效 -->
         <!-- 设定JDBC 的Statement 读取数据的时候每次从数据库中取出的记录的条数 -->
         <property name="hibernate.jdbc.fetch_size">100</property>

         <!-- 设置数据库进行批量删除，批量更新和批量插入的时候的大小 -->
         <property name="hibernate.jdbc.batch_size">30</property>

         <!-- 指定关联的 .hbm.xml 文件 -->
         <!--
             <mapping resource="hibernate/helloworld/News.hbm.xml"/>
             <mapping resource="hibernate/helloworld/Worker.hbm.xml"/>

             <mapping resource="com/jason/hibernate/entities/n21/Customer.hbm.xml"/>
             <mapping resource="com/jason/hibernate/entities/n21/Order.hbm.xml"/>
         -->

          <mapping resource="com/jason/hibernate/entities/n21/both/Customer.hbm.xml"/>
          <mapping resource="com/jason/hibernate/entities/n21/both/Order.hbm.xml"/>       

         <!-- 1-1 映射 -->
         <!-- 基于外键实现 -->
         <!-- <mapping resource="com/jason/hibernate/entities/foreign/one2one/Manager.hbm.xml"/>
         <mapping resource="com/jason/hibernate/entities/foreign/one2one/Department.hbm.xml"/>
          -->
         <!-- 基于主键实现 -->
         <mapping resource="com/jason/hibernate/entities/primary/one2one/Manager.hbm.xml"/>
         <mapping resource="com/jason/hibernate/entities/primary/one2one/Department.hbm.xml"/>

     </session-factory>

 </hibernate-configuration>

HibernateTest.java

 package com.jason.hibernate.entities.foreign.one2one;

 import hibernate.helloworld.News;

 import java.util.Date;

 import org.hibernate.Hibernate;
 import org.hibernate.Session;
 import org.hibernate.SessionFactory;
 import org.hibernate.Transaction;
 import org.hibernate.cfg.Configuration;
 import org.hibernate.service.ServiceRegistry;
 import org.hibernate.service.ServiceRegistryBuilder;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;

 public class HibernateTest {

     private SessionFactory sessionFactory;
     private Session session;
     private Transaction transaction;
     @Test
     public void test() {

         // 1. 创建一个SessionFatory 对象
         SessionFactory sessionFactory = null;

         // 1) 创建Configuration 对象：对应hibernate 的基本配置信息 和 对象关系映射信息
         Configuration configuration = new Configuration().configure();

         // 2) 创建一个ServiceRegistry 对象：hibernate 4.x 新天添加的对象。
         // hibernate 的任何配置 和 服务都需要在该对象中注册后才有效
         ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
                 .applySettings(configuration.getProperties())
                 .buildServiceRegistry();

         // sessionFactory = configuration.buildSessionFactory();
         sessionFactory = configuration.buildSessionFactory(serviceRegistry);

         // 2. 创建一个session 对象
         Session session = sessionFactory.openSession();

         // 3. 开启事物
         Transaction transaction = session.beginTransaction();

         // 4.执行保存操作
         News news = new News("java", "jason", new Date(
                 new java.util.Date().getTime()));
         session.save(news);

         // 5.提交事物
         transaction.commit();
         // 6.关闭session
         session.close();
         // 7.关闭SessionFactory 对象
         sessionFactory.close();
     }

     // 创建上述三个对象
     @Before
     public void init() {
         Configuration configuration = new Configuration().configure();
         ServiceRegistry serviceRegistry = new ServiceRegistryBuilder()
                 .applySettings(configuration.getProperties())
                 .buildServiceRegistry();

         sessionFactory = configuration.buildSessionFactory(serviceRegistry);

         session = sessionFactory.openSession();

         transaction = session.beginTransaction();
     }

     // 关闭上述三个对象
     @After
     public void destroy() {
         transaction.commit();
         session.close();
         sessionFactory.close();
     }

     @Test
     public void testSave(){

         Department department = new Department();
         department.setDeptName("DEPT-BB");

         Manager manager = new Manager();
         manager.setMgrName("MGR-BB");

         //设定关联关系
         department.setMgr(manager);
         manager.setDept(department);

         //保存
         //建议先保存没有外键列的那个对象，这样会减少update 语句
         session.save(manager);
         session.save(department);

     }

     @Test
     public void testGet(){

         //1.默认情况下对关联属性使用懒加载
         Department dept = (Department) session.get(Department.class, 1);
         System.out.println(dept.getDeptName());

         //2.查询Manager 对象的连接条件应该是dept.manager_id = mgr.manager_id
         //而不因该是  manager0_.MGR_ID=department1_.DEPT_ID
         Manager mgr = dept.getMgr();
         System.out.println(mgr);
     }

     @Test
     public void testGet2(){

         //在查询没有外键的实体对象，使用的是左外连接查询，一并查询出其关联的对象，并已经进行初始化
         Manager manager = (Manager) session.get(Manager.class, 1);
         System.out.println(manager);

         System.out.println(manager.getDept().getDeptName());

     }

 }