Hibernate 学习代码/笔记(四)(一对多)-优快云博客

本文链接：https://blog.youkuaiyun.com/Simba_cheng/article/details/50408219

本文介绍了一个使用Hibernate实现的单向一对多关系映射示例。通过班级和学生两个实体，展示了如何在Java中配置一对多的关系，并提供了完整的代码实现。

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先来张代结果码图吧..

好了.....首先实体类

班级类

package com.hibernate.entity;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;

/**
 * 单向一对多
 * 一个班级对应多个学生
 * @author cyx
 *
 */
public class Grade implements Serializable {
	
	private int gid;
	private String gname;
	private String gdesc;
	
	//在一方定义一个多方的集合
	private Set<Student> student = new HashSet<Student>();
		
	public Set<Student> getStudent() {
		return student;
	}
	public void setStudent(Set<Student> student) {
		this.student = student;
	}
	public int getGid() {
		return gid;
	}
	public void setGid(int gid) {
		this.gid = gid;
	}
	public String getGname() {
		return gname;
	}
	public void setGname(String gname) {
		this.gname = gname;
	}
	public String getGdesc() {
		return gdesc;
	}
	public void setGdesc(String gdesc) {
		this.gdesc = gdesc;
	}
	public Grade(String gname, String gdesc) {
//		super();
		this.gname = gname;
		this.gdesc = gdesc;
	}
	public Grade() {
//		super();
	}
}

学生类:

package com.hibernate.entity;

/**
 * 
 * @author cyx
 *
 */
public class Student {
	
	private int sid;
	private String sname;
	private String sex;
	
	
	public int getSid() {
		return sid;
	}
	public void setSid(int sid) {
		this.sid = sid;
	}
	public String getSname() {
		return sname;
	}
	public void setSname(String sname) {
		this.sname = sname;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	@Override
	public String toString() {
		return "Student [sid=" + sid + ", sname=" + sname + ", sex=" + sex
				+ "]";
	}
	public Student(String sname, String sex) {
//		super();
		this.sname = sname;
		this.sex = sex;
	}
	public Student() {
//		super();
	}
}

hibernate实体类配置文件

<?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">

<!-- 班级对象关系映射 -->
<hibernate-mapping>
    <class name="com.hibernate.entity.Grade" table="grade" >
    	<id name="gid" type="integer" column="gid">    		
    		<generator class="increment"/>
    	</id>
    	<property name="gname" type="string" column="gname" not-null="true" length="20"></property>
    	<property name="gdesc" column="gdesc"></property>

    	<!-- 配置单向一对多关联关系 -->
    	<set name="student" table="student">
    		<key column="gid"></key>	<!-- 指定关联的外键 -->
    		<one-to-many class="com.hibernate.entity.Student"/>
    	</set>
    	
    	<!-- 
    		set元素常用属性:
    			name:	映射类属性的名称 也就是Garade实体类中,添加的student set集合
    			table:	关联类的目标数据库
    			lazy:	指定关联对象是否使用延时加载	默认为 proxy
    			inverse:表示双向关联中被动的一方		默认为 false
    	 -->
    	
    </class>
</hibernate-mapping>

<?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">

<!-- 学生的对象关系映射 -->
<hibernate-mapping>
    <class name="com.hibernate.entity.Student"  table="student">
    	<id name="sid" type="int" column="sid">
    		<generator class="increment"/>
    	</id>
    	<property name="sname" type="java.lang.String" column="sname" length="20" not-null="true"></property>
    	<property name="sex" type="java.lang.String" column="sex"></property>

    	
    </class>

</hibernate-mapping>

hibernate 主配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
		"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
		"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
    <session-factory>
    	<property name="connection.username">root</property>		<!-- 数据库用户名 -->
		<property name="connection.password">1234</property>		<!-- 数据库密码 -->
		<property name="connection.driver_class">com.mysql.jdbc.Driver</property><!-- 数据库驱动 -->
		<!-- 数据库地址 -->
		<property name="connection.url">jdbc:mysql://localhost:3306/test?user=root&password=1234&useUnicode=true&characterEncoding=UTF-8</property>
		<property name="dialect">org.hibernate.dialect.MySQLDialect</property><!-- mysql 数据库方言 -->
		
		
		<property name="show_sql">true</property>		
		<property name="format_sql">false</property>		
		<property name="hbm2ddl.auto">update</property>
		
		<mapping resource="com/hibernate/entity/Grade.hbm.xml"/>
		<mapping resource="com/hibernate/entity/Student.hbm.xml"/>
		
    </session-factory>
</hibernate-configuration>

hibernate getSession

package com.hibernate.util;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
import org.hibernate.service.ServiceRegistry;
import org.hibernate.service.ServiceRegistryBuilder;

public class HibernateUtil {

	private static SessionFactory sessionFactory;
	private static Session session;
	
	static {
		//创建配置对象
		Configuration config = new Configuration().configure();
		//创建服务注册对象
		ServiceRegistry serviceRegistry = new ServiceRegistryBuilder().applySettings(config.getProperties()).buildServiceRegistry();
		//创建会话工厂对象
		sessionFactory = config.buildSessionFactory(serviceRegistry);
		//创建会话对象
//		session = sessionFactory.openSession();			
	}
	
	//获取sessionFactory
	public static SessionFactory getSessionFactory(){
		return sessionFactory;
	}
	
	//获取session
	public static Session getSession(){
		session = sessionFactory.openSession();
		return session;
	}
	
	//关闭session
	public static void closeSession(Session session){
		if(session != null){
			session.close();			
		}
	}
}

测试代码

package com.hibernater.test;

import java.util.Set;

import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;

import com.hibernate.entity.Grade;
import com.hibernate.entity.Student;
import com.hibernate.util.HibernateUtil;

public class TestOneToMany {
	
	private Session session;
	private HibernateUtil hibernateUtil;
	private Transaction transaction;
	
	
	/**
	 * 添加学生
	 */
	@Test
	public void add(){
		try{
			session = hibernateUtil.getSession();
			transaction = session.beginTransaction();
			
			Grade grade = new Grade("JAVA一班", "软件开发");
			Student student = new Student("小明", "男");
			Student student2 = new Student("大明", "女");
			
			//如果希望在学生表中添加对应的班级编号,需要在班级中添加学生,建立关系链接
			grade.getStudent().add(student);
			grade.getStudent().add(student2);
			
			session.save(grade);
			session.save(student);
			session.save(student2);
			
			transaction.commit();			
		}catch(Exception e){
			transaction.rollback();
			e.printStackTrace();
		}finally{
			if(session != null){
				hibernateUtil.closeSession(session);
			}
		}
	}
	
	
	/**
	 * 查询班级中包含的学生
	 */
	@Test
	public void findStudentByGrade(){
		session = hibernateUtil.getSession();
		Grade grade = (Grade)session.get(Grade.class, 1);
		System.out.println(grade.getGname()+","+grade.getGdesc());
		
		Set<Student> student = grade.getStudent();
		for (Student student2 : student) {
			System.out.println(student2.getSname()+","+student2.getSex());
		}		
	}
	
	
	/**
	 * 修改学生所属班级
	 */
	@Test
	public void update(){
		try{
			session = hibernateUtil.getSession();
			transaction = session.beginTransaction();
			
			Grade grade = new Grade("PHP一班","软件开发");
			Student studet = (Student)session.get(Student.class, 1);
			grade.getStudent().add(studet);
			session.save(grade);
			transaction.commit();
		}catch(Exception e){
			transaction.rollback();
			e.printStackTrace();
		}finally{
			if(session != null){
				hibernateUtil.closeSession(session);
			}
		}
	}
	
	
	/**
	 * 删除学生
	 */
	@Test
	public void delete(){
		try{
			session = hibernateUtil.getSession();
			Transaction transaction = session.beginTransaction();
			
			Student student = (Student)session.get(Student.class, 1);			
			session.delete(student);
			transaction.commit();
			
		}catch(Exception e){
			e.printStackTrace();
			transaction.rollback();
		}finally{
			if(session != null){
				hibernateUtil.closeSession(session);
			}
		}
	}
}

over...