4.一对多单向关联(班级对学生):测试

最新推荐文章于 2017-05-19 10:51:58 发布

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最新推荐文章于 2017-05-19 10:51:58 发布

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分类专栏： Hibernate

本文链接：https://blog.youkuaiyun.com/seeds_home/article/details/7916241

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本文详细介绍了如何使用Hibernate框架实现Java对象之间的One-to-Many关系，包括实例化对象、设置关联关系及加载操作，并讨论了在操作过程中可能出现的异常及解决方法。

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package com.bjpowernode.hibernate;

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

import org.hibernate.Session;

import junit.framework.TestCase;

public class One2ManyTest extends TestCase {

	public void testSave1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			Student student1 = new Student();
			student1.setName("张三");
			
			Student student2 = new Student();
			student2.setName("李四");
			
			Classes classes = new Classes();
			classes.setName("动力节点");
			
			Set students = new HashSet();
			students.add(student1);
			students.add(student2);
			classes.setStudents(students);
			
			//抛出TransientObjectException
			//因为Student不是Persistent状态的对象,它是Transient状态的对象
			session.save(classes);
			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}
	
	public void testSave2() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			Student student1 = new Student();
			student1.setName("张三");
			session.save(student1);
			
			Student student2 = new Student();
			student2.setName("李四");
			session.save(student2);
			
			Classes classes = new Classes();
			classes.setName("动力节点");
			
			Set students = new HashSet();
			students.add(student1);
			students.add(student2);
			classes.setStudents(students);
			
			//可以成功保存数据
			//但是会发出多余的update语句来维持关系
			session.save(classes);
			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}	
	
	public void testLoad1() {
		Session session = null;
		try {
			session = HibernateUtils.getSession();
			session.beginTransaction();
			Classes classes = (Classes)session.load(Classes.class, 2);
			System.out.println("classes.name=" + classes.getName());
			Set students = classes.getStudents();
			for (Iterator iter=students.iterator(); iter.hasNext();) {
				Student student = (Student)iter.next();
				System.out.println("student.name=" +student.getName());
			}
			session.getTransaction().commit();
		}catch(Exception e) {
			e.printStackTrace();
			session.getTransaction().rollback();
		}finally {
			HibernateUtils.closeSession(session);
		}
	}		
}