【7.6】基于List集合映射

1.Grade类

package cn.siggy.pojo;

import java.util.ArrayList;
import java.util.List;

public class Grade {
	private int id;
	private String name;
	private List<Student> students = new ArrayList<Student>(0);
	
       /*get/set*/
}    

　　

2.Student类

package cn.siggy.pojo;

public class Student {
	private int id;
	private String name;
	private int age;
	/*get/set*/
}

　　

3.映射文件

Grade.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="cn.siggy.pojo">
	<class name="Grade">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<list name="students" cascade="all">
			<!-- key表示外键  column外键列名-->
			<key column="grade_id"></key>
			<!-- 在多的一端 产生一列 用来表示顺序 如果不指明列名 默认为 idx 
				值由hibernate来维护
			 -->
			<list-index column="sort"/>
			<!-- one-to-many 一对多  类Grade 中  students 所表示类型 -->
			<one-to-many class="Student"/>
		</list>
	</class>
</hibernate-mapping>

　　

Student.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="cn.siggy.pojo">
	<class name="Student">
		<id name="id" column="sid">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<property name="age"/>
	</class>
</hibernate-mapping>

　　

4.测试代码

package cn.siggy.test;

import java.sql.SQLException;
import java.util.List;

import javax.sql.rowset.serial.SerialException;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
import org.hibernate.cfg.Configuration;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.junit.Test;

import cn.siggy.pojo.Grade;
import cn.siggy.pojo.Student;
import cn.siggy.util.HibernateUtil;

public class HibernateTest {
	@Test
	public void testCreateDB(){
		Configuration cfg = new Configuration().configure();
		SchemaExport se = new SchemaExport(cfg);
		//第一个参数 是否生成ddl脚本  第二个参数  是否执行到数据库中
		se.create(true, true);
	}
	@Test
	public void testSave() throws HibernateException, SerialException, SQLException{
		Configuration cfg = new Configuration().configure();
		SessionFactory factory = cfg.buildSessionFactory(new StandardServiceRegistryBuilder()
		.applySettings(cfg.getProperties()).build());
		Session session = null;
		Transaction tx = null;
		try{
			session = factory.openSession();
			tx = session.beginTransaction();
			Grade grade = new Grade();
			grade.setName("基础");
			
			Student stu = new Student();
			stu.setName("张三疯");
			stu.setAge(22);
			Student stu1 = new Student();
			stu1.setName("老王");
			stu1.setAge(23);
			Student stu2 = new Student();
			stu2.setName("老李");
			stu2.setAge(23);
			//关联
			grade.getStudents().add(stu);
			grade.getStudents().add(stu1);
			grade.getStudents().add(stu2);
			//保存数据的顺序 是根据外键的配置来决定的
			//如果外键不能为null,那么先保存一的一端
			//如果外键可以为null,则可以随意保存
			session.save(grade);
			session.save(stu);
			session.save(stu1);
			session.save(stu2);
			
			tx.commit();
			
		}catch (HibernateException e) {
			if(tx!=null)
				tx.rollback();
			e.printStackTrace();
			throw e;
		}finally{
			HibernateUtil.closeSession();
		}
	}
	@Test
	public void testGet(){
		Session session = null;
		Transaction tx = null;
		try{
			session = HibernateUtil.getSession();
			tx = session.beginTransaction();
			//取数据
			Grade grade = (Grade)session.get(Grade.class, 1);
			System.out.println("gradeName="+grade.getName());
			System.out.println("grade所对应的多的一端的数据");
			List<Student> list = grade.getStudents();
			for(Student stu:list){
				System.out.println(stu.getName());
			}
			tx.commit();
		}catch (HibernateException e) {
			if(tx!=null)
				tx.rollback();
			e.printStackTrace();
			throw e;
		}finally{
			HibernateUtil.closeSession();
		}
	}
}

　　

5.测试结果

1.执行testSave()方法：

 

2.执行testGet():