【7.1】单向一对多映射

1.Grade类

package cn.siggy.pojo;

import java.util.HashSet;
import java.util.Set;

public class Grade {
	private int id;
	private String name;
	private Set<Student> students = new HashSet<Student>(0);
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public Set<Student> getStudents() {
		return students;
	}
	public void setStudents(Set<Student> students) {
		this.students = students;
	}
}

　　

2.Student类

package cn.siggy.pojo;

public class Student {
	private int id;
	private String name;
	private int age;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
}

　　

3.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"/>
		<!-- set是 Grade中的集合属性  name属性名称 -->
		<set name="students">
			<!-- key表示外键  column外键列名-->
			<key column="grade_id" not-null="true"></key>
			<!-- one-to-many 一对多  类Grade 中  students 所表示类型 -->
			<one-to-many class="Student"/>
		</set>
	</class>
</hibernate-mapping>

　　

4.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">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<property name="age"/>
	</class>
</hibernate-mapping>

　　

5。测试代码【依次单位测试运行@Tes 】

package cn.siggy.test;

import java.sql.SQLException;
import java.util.Iterator;

import javax.sql.rowset.serial.SerialException;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.Transaction;
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{
		Session session = null;
		Transaction tx = null;
		try{
			session = HibernateUtil.getSession();
			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);
			//关联
			grade.getStudents().add(stu);
			grade.getStudents().add(stu1);
			//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);
			
			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");
			Iterator<Student> iter = grade.getStudents().iterator();
			for(;iter.hasNext();){
				Student temp = iter.next();
				System.out.println("name="+temp.getName()+"\tage="+temp.getAge());
			}
			tx.commit();
		}catch (HibernateException e) {
			if(tx!=null)
				tx.rollback();
			e.printStackTrace();
			throw e;
		}finally{
			HibernateUtil.closeSession();
		}
	}
}

　　

6.测试结果