Hibernate学习笔记三（之）——关联关系一对多映射

项目总览图：

Class.java

package com.java1234.model;

public class Class {
	private long id;
	private String name;
	private Class c;

	//...省略get&setter
}

Student.java

public class Student {
	
	private long id;
	private String name;
	private Class c;
        //...省略get&set方法
}

Class.hbm.xml

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.java1234.model">
	<class name="Class" table="t_class"><!-- table="t_student" 对应数据库的表明 -->
		<!-- 主键 -->
		<id name="id" column="classId">
			<generator class="native"></generator>
		</id>
		<property name="name" column="className"></property>
	</class>
</hibernate-mapping>

Student.hbm.xml  主要配置项：<many-to-one name="c" column="classId" class="com.java1234.model.Class"></many-to-one>

在<many-to-one>这端，cascade 默认是”none”，假如我们希望在持久化多的一端的时候，自动级 联保存和更新一的一端，我们可以把 cascade 设置成”save-update”；

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="com.java1234.model">
	<class name="Student" table="t_student"><!-- table="t_student" 对应数据库的表明 -->
		<!-- 主键 -->
		<id name="id" column="stuId">
			<generator class="native"></generator>
		</id>
		<property name="name" column="stuName"></property>
		<many-to-one name="c" column="classId" class="com.java1234.model.Class"></many-to-one>
	</class>
</hibernate-mapping>

HibernateUtil.java

package com.java1234.util;

import org.hibernate.SessionFactory;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;

public class HibernateUtil {
	private static final SessionFactory sessionFactory = buildSessionFactory();
	
	private static SessionFactory buildSessionFactory() {
		Configuration configuration = new Configuration().configure();
		ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder().applySettings(configuration.getProperties()).build();//实例化服务登记
		SessionFactory sessionFactory = configuration.buildSessionFactory(serviceRegistry);//获取Session工厂
		return sessionFactory;
	}
	
	public static SessionFactory getSessionFactory() {
		return sessionFactory;
	}
}

hibernate.cfg.xml

<?xml version='1.0' encoding='utf-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

    <session-factory>

        <!--数据库连接设置 -->
        <property name="connection.driver_class">com.mysql.jdbc.Driver</property>
        <property name="connection.url">jdbc:mysql://localhost:3306/hibernate</property>
        <property name="connection.username">root</property>
        <property name="connection.password">root</property>

       
        <!-- 方言 -->
        <property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
	
        <!-- 控制台显示SQL -->
        <property name="show_sql">true</property>

        <!-- 自动更新表结构 -->
        <property name="hbm2ddl.auto">update</property>
        
  		<mapping resource="com/java1234/model/Student.hbm.xml"/>
  		<mapping resource="com/java1234/model/Class.hbm.xml"/>
    </session-factory>

</hibernate-configuration>

test方法：

StudentTest.java

package com.java1234.service;

import org.hibernate.Session;
import org.hibernate.SessionFactory;

import com.java1234.model.Class;
import com.java1234.model.Student;
import com.java1234.util.HibernateUtil;

public class StudentTest {
	
	public static void main(String[] args) {
		
		SessionFactory sessionFactory = HibernateUtil.getSessionFactory();
		Session session = sessionFactory.openSession();//生成一个session会话
		session.beginTransaction();//开启事务
		
		Class c = new Class();
		c.setName("08计本");
		session.save(c);
		
		Student s1 = new Student();
		s1.setName("张三");
		s1.setC(c);
		
		Student s2 = new Student();
		s2.setName("李四");
		s2.setC(c);
		
		session.save(s1);
		session.save(s2);
		
		session.getTransaction().commit();//提交事务
		session.close();//关闭session
		
	}
	
}

数据库结果：

数据库架构图：