7.0单向多对一的关联映射

Posted 2020-09-08 chxbar.cn

1.学生表student 和年级表 grade

 

2.类Student 和Grade类

public class Student {
	private int id;
	private String name;
	private int age;
	private Grade grade;
//get…set
}

---

public class Grade {
	private int id;
	private String name;
	//get…set
}

 

3.映射文件

Grade.hbm.xml：

<hibernate-mapping package="cn.siggy.pojo">
	<class name="Grade">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
	</class>
</hibernate-mapping>

 Student.hbm.xml:

<hibernate-mapping package="cn.siggy.pojo">
	<class name="Student">
		<id name="id">
			<generator class="native"></generator>
		</id>
		<property name="name"/>
		<property name="age"/>
		<!-- 多对一  name 表示属性名  class 指明 属性对应的类 
		 column指 数据库表中的列名 -->
			<many-to-one name="grade" class="Grade" 
		column="grade_id" foreign-key="fk_grade" not-null="true"/>	
</class>
</hibernate-mapping>

 

4.测试代码

 

package cn.siggy.test;

import java.sql.SQLException;

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");
			session.save(grade);
			Student stu = new Student();
			stu.setName("张三疯");
			stu.setAge(22);
			stu.setGrade(grade);
			session.save(stu);
			
			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
			Student stu = (Student)session.get(Student.class, 1);
			System.out.println("student——name:"+stu.getName()+"--grade-name:"+stu.getGrade().getName());
			tx.commit();
		}catch (HibernateException e) {
			if(tx!=null)
				tx.rollback();
			e.printStackTrace();
			throw e;
		}finally{
			HibernateUtil.closeSession();
		}
	}
}

　　

5.测试结果

控制台信息：

 

数据库表信息：