Hibernate基于配置文件（十三）多对多双向关联映射及其拆分

原创 于 2014-02-20 16:50:27 发布 · 140 阅读 · 0 ·
CC 4.0 BY-SA版权
版权声明：本文为博主原创文章，遵循 CC 4.0 BY-SA 版权协议，转载请附上原文出处链接和本声明。
文章标签：

#java #数据库

本文介绍在Hibernate中实现多对多关联的方法，包括直接使用中间表和引入第三方类两种方式。通过示例展示了如何定义实体类及映射文件，并提供测试代码验证功能。

摘要生成于 C知道 ，由 DeepSeek-R1 满血版支持， 前往体验 >


 

多对多关联，都会引入第三张表


package org.leadfar.hibernate.model;

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


public class Person {
	private int id;
	private String name;
	private Set<Role> roles;
	
	Person(){}
	
	//给人分配角色
	public void addRole(Role role) {
		if(roles==null) {
			roles = new HashSet<Role>();
		}
		roles.add(role);
	}
	
	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<Role> getRoles() {
		return roles;
	}

	public void setRoles(Set<Role> roles) {
		this.roles = roles;
	}

	
}

 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
	package="org.hibernate.auction">
	<class name="org.leadfar.hibernate.model.Person" table="t_persons" >
		<!-- id为数据库标识，作为主键 -->
		<id name="id">
			<generator class="native">
			</generator>
		</id>
		<property name="name"/>
		
		<!-- t_person_role为中间表，记录Person的id与Role的id -->
		<set name="roles" table="t_person_role">
		<!-- key column="personId" 表示在t_person_role表中用personId字段来记录Person的id-->
			<key column="personId"></key>
			<!-- class指名对方是哪个类--由类即能确定表， colunm指定保存对方id的字段，通过column的id值就能到对应表中取出记录-->
			<many-to-many class="org.leadfar.hibernate.model.Role" column="roleId"></many-to-many>
		</set>
		
	</class>
	
</hibernate-mapping>

 

package org.leadfar.hibernate.model;

import java.util.Set;

public class Role {
	private int id;
	private String name;
	private Set<Person> persons;
	
	
	Role(){}
	
	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<Person> getPersons() {
		return persons;
	}
	public void setPersons(Set<Person> persons) {
		this.persons = persons;
	}
	
}

 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
	package="org.hibernate.auction">
	<class name="org.leadfar.hibernate.model.Role" table="t_roles" >
		<!-- id为数据库标识，作为主键 -->
		<id name="id">
			<generator class="native"/>
		</id>
		<property name="name"/>		
		<!-- 表一致 都为t_person_role -->
		<set name="persons" table="t_person_role">
		<!-- 用roleId记录本方Role -->
			<key column="roleId"></key>
			<!-- 用personId记录对方的id -->
			<!-- 注意：两张表的表名字段名都必须一致，才能将关系存储到一张表中！ -->
			<many-to-many class="org.leadfar.hibernate.model.Person" column="personId"></many-to-many>
		</set>
	</class>
	
</hibernate-mapping>

 

测试

package org.leadfar.hibernate.model;

import java.util.Set;

import junit.framework.TestCase;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class Many2ManyTest extends TestCase {
	
	public void many2many_save() {
		Configuration cfg = new Configuration().configure();
		SessionFactory sf = cfg.buildSessionFactory();
		Session session = sf.openSession();
		
		try {
			session.beginTransaction();
			
			Person p1= new Person();
			p1.setName("1abc");
			session.save(p1);
			
			Person p2= new Person();
			p2.setName("2abc");
			session.save(p2);
			
			Person p3= new Person();
			p3.setName("3abc");
			session.save(p3);
			
			Role r1 = new Role();
			r1.setName("系统管理员");
			session.save(r1);
			
			Role r2 = new Role();
			r2.setName("档案管理员");
			session.save(r2);
			
			Role r3 = new Role();
			r3.setName("项目管理员");
			session.save(r3);
			
			p1.addRole(r3);
			p1.addRole(r2);
			
			p2.addRole(r1);
			
			p3.addRole(r3);
			p3.addRole(r2);
			p3.addRole(r1);
			
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			session.close();
		}
	}
	public void many2many_load01() {
		Configuration cfg = new Configuration().configure();
		SessionFactory sf = cfg.buildSessionFactory();
		Session session = sf.openSession();
		
		try {
			session.beginTransaction();
		
			Person p = (Person)session.load(Person.class, 3);
			Set<Role> role = p.getRoles();
			for(Role r : role) {
				System.out.println(p.getName()+","+r.getName());
			}
			
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			session.close();
		}
	}
	public void many2many_load02() {
		Configuration cfg = new Configuration().configure();
		SessionFactory sf = cfg.buildSessionFactory();
		Session session = sf.openSession();
		
		try {
			session.beginTransaction();
			
			Role r = (Role)session.load(Role.class, 3);
			Set<Person> persons = r.getPersons();
			for(Person p : persons) {
				System.out.println(r.getName()+","+p.getName());
			}
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			session.close();
		}
	}
	
	
	
}

 

 

====================================================================

 

拆分多对多--->2个一对多

多的一方(PersonRole)，关联两个一的一端（Person,Role）

引入第三个类，不但可以保持关联关系，并可以在类中增加额外属性

而且避免了对集合的操作，在多的一端进行操作即可！

 

package org.leadfar.hibernate.model;


import java.util.Set;


public class Person {
	private int id;
	private String name;
	private Set<PersonRole> personRoles;
	
	Person(){}
	

	
	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<PersonRole> getPersonRoles() {
		return personRoles;
	}

	public void setPersonRoles(Set<PersonRole> personRoles) {
		this.personRoles = personRoles;
	}

	

	
}

   

package org.leadfar.hibernate.model;

import java.util.Set;

public class Role {
	private int id;
	private String name;
	private Set<PersonRole> rolePersons;
	
	
	Role(){}
	
	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<PersonRole> getRolePersons() {
		return rolePersons;
	}

	public void setRolePersons(Set<PersonRole> rolePersons) {
		this.rolePersons = rolePersons;
	}


	
}

 

 

package org.leadfar.hibernate.model;

import java.util.Date;

public class PersonRole {
	/**
	 * PersonRole作为多的一方，持有Person和Role的引用
	 * 
	 */
	private int id;
	private Person person;
	private Role role;
	private Date createTime;
	
	PersonRole(){}
	
	public PersonRole(Person person,Role role) {
		this.person = person;
		this.role = role;
		this.createTime = new Date();
	}
	
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public Person getPerson() {
		return person;
	}
	public void setPerson(Person person) {
		this.person = person;
	}
	public Role getRole() {
		return role;
	}
	public void setRole(Role role) {
		this.role = role;
	}
	public Date getCreateTime() {
		return createTime;
	}
	public void setCreateTime(Date createTime) {
		this.createTime = createTime;
	}
	
	
}

 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
	package="org.hibernate.auction">
	<class name="org.leadfar.hibernate.model.Person" table="t_persons" >
		<!-- id为数据库标识，作为主键 -->
		<id name="id">
			<generator class="native">
			</generator>
		</id>
		<property name="name"/>
		
		<set name="personRoles" lazy="extra" inverse="true">
			<key column="personId"></key>
			<one-to-many class="org.leadfar.hibernate.model.PersonRole"></one-to-many>
		</set>
		
	</class>
	
</hibernate-mapping>

 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
	package="org.hibernate.auction">
	<class name="org.leadfar.hibernate.model.Role" table="t_roles" >
		<!-- id为数据库标识，作为主键 -->
		<id name="id">
			<generator class="native"/>
		</id>
		<property name="name"/>		
		<set name="rolePersons" lazy="extra" inverse="true">
			<key column="roleId"></key>
			<one-to-many class="org.leadfar.hibernate.model.PersonRole"></one-to-many>
		</set>
	</class>
	
</hibernate-mapping>

 

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC 
	"-//Hibernate/Hibernate Mapping DTD 3.0//EN"
	"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping 
	package="org.hibernate.auction">
	<class name="org.leadfar.hibernate.model.PersonRole" table="t_person_role" >
		<!-- id为数据库标识，作为主键 -->
		<id name="id">
			<generator class="native"/>
		</id>
		<many-to-one name="person" column="personId"></many-to-one>
		<many-to-one name="role" column="roleId"></many-to-one>
		<property name="createTime" type="timestamp"></property>
	</class>
	
</hibernate-mapping>

 

测试

package org.leadfar.hibernate.model;


import java.util.Set;

import junit.framework.TestCase;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;

public class Many2ManyTest extends TestCase {
	
	public void many2many_save() {
		Configuration cfg = new Configuration().configure();
		SessionFactory sf = cfg.buildSessionFactory();
		Session session = sf.openSession();
		
		try {
			session.beginTransaction();
			
			Person p1= new Person();
			p1.setName("1abc");
			session.save(p1);
			
			Person p2= new Person();
			p2.setName("2abc");
			session.save(p2);
			
			Person p3= new Person();
			p3.setName("3abc");
			session.save(p3);
			
			Role r1 = new Role();
			r1.setName("系统管理员");
			session.save(r1);
			
			Role r2 = new Role();
			r2.setName("档案管理员");
			session.save(r2);
			
			Role r3 = new Role();
			r3.setName("项目管理员");
			session.save(r3);
			
			//从多的一端维护关联关系
			session.save(new PersonRole(p1,r1));
			session.save(new PersonRole(p2,r2));
			session.save(new PersonRole(p3,r1));
			session.save(new PersonRole(p3,r2));
			session.save(new PersonRole(p3,r3));
			
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			session.close();
		}
	}
	public void many2many_load01() {
		Configuration cfg = new Configuration().configure();
		SessionFactory sf = cfg.buildSessionFactory();
		Session session = sf.openSession();
		
		try {
			session.beginTransaction();
		
			Person p = (Person)session.load(Person.class, 3);
		
			Set<PersonRole> prs = p.getPersonRoles();
			for(PersonRole pr : prs) {
				System.out.println(p.getName()+","+pr.getRole().getName());
			}
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			session.close();
		}
	}
	public void many2many_load02() {
		Configuration cfg = new Configuration().configure();
		SessionFactory sf = cfg.buildSessionFactory();
		Session session = sf.openSession();
		
		try {
			session.beginTransaction();
			
			Role r = (Role)session.load(Role.class, 3);
		
			Set<PersonRole> prs = r.getRolePersons();
			for(PersonRole pr : prs) {
				System.out.println(r.getName()+","+pr.getPerson().getName());
			}
			
			session.getTransaction().commit();
			
		} catch(Exception e) {
			session.getTransaction().rollback();
			e.printStackTrace();
		} finally {
			session.close();
		}
	}
	

	
}

 

=================================================================

 

 分析对象之间的关系：

1个用户拥有多个组，1个组只属于1个用户；

1个用户可以属于多个组（1个学生只属于1个班级），1个组可以包含多个用户；



 

评论
添加红包

请填写红包祝福语或标题

个

红包个数最小为10个

元

红包金额最低5元

当前余额3.43元 前往充值 >
需支付：10.00元
成就一亿技术人!
领取后你会自动成为博主和红包主的粉丝 规则
hope_wisdom
发出的红包
实付元
使用余额支付
点击重新获取
扫码支付
钱包余额 0

抵扣说明：

1.余额是钱包充值的虚拟货币，按照1:1的比例进行支付金额的抵扣。
2.余额无法直接购买下载，可以购买VIP、付费专栏及课程。

余额充值