Hibernate关系映射：多对多关联
N-N关联映射增加一张表才完成基本映射。
与1-N映射相似，必须为set集合元素添加key子元素，指定CATEGORIES_ITEMS表中参照CATEGORIES表的外键为CATEGORIY_ID。
与1-N不同的是，建立N-N关联时，集合中的元素使用many-to-many。关于配置文件的属性的介绍，将在代码实现部分介绍。
数据库设计：
案例：
角色表实体类：
package com.liuyongqi.MavenHibernateDemo6.entity;
import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
/**
* 角色表实体类
* @author Administrator
* @data 2018年8月7日
* @time 上午10:52:16
*/
public class Roles implements Serializable {
/**
*
*/
private static final long serialVersionUID = -3594387215393055820L;
private Integer rid; //角色编号
private String rname; //角色名称
private Set<Users> usersSet=new HashSet<Users>(); //用户集合
public Roles() {
super();
// TODO Auto-generated constructor stub
}
public Roles(String rname) {
super();
this.rname = rname;
}
public Roles(Integer rid, String rname) {
super();
this.rid = rid;
this.rname = rname;
}
public Integer getRid() {
return rid;
}
public void setRid(Integer rid) {
this.rid = rid;
}
public String getRname() {
return rname;
}
public void setRname(String rname) {
this.rname = rname;
}
public Set<Users> getUsersSet() {
return usersSet;
}
public void setUsersSet(Set<Users> usersSet) {
this.usersSet = usersSet;
}
@Override
public String toString() {
return "Roles [rid=" + rid + ", rname=" + rname + "]";
}
}
用户实体类：
package com.liuyongqi.MavenHibernateDemo6.entity;
import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
/**
* 用户实体类
* @author Administrator
* @data 2018年8月7日
* @time 上午10:50:09
*/
public class Users implements Serializable {
/**
*
*/
private static final long serialVersionUID = -7658139381686355418L;
private Integer uid; //用户编号
private String uname; //用户名称
private Set<Roles> rolesSet=new HashSet<Roles>(); //角色集合
public Users() {
super();
// TODO Auto-generated constructor stub
}
public Users(String uname) {
super();
this.uname = uname;
}
public Users(Integer uid, String uname) {
super();
this.uid = uid;
this.uname = uname;
}
public Integer getUid() {
return uid;
}
public void setUid(Integer uid) {
this.uid = uid;
}
public String getUname() {
return uname;
}
public void setUname(String uname) {
this.uname = uname;
}
public Set<Roles> getRolesSet() {
return rolesSet;
}
public void setRolesSet(Set<Roles> rolesSet) {
this.rolesSet = rolesSet;
}
@Override
public String toString() {
return "Users [uid=" + uid + ", uname=" + uname + "]";
}
}
SessionFactoryUtil工具类：
package com.liuyongqi.MavenHibernateDemo6.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
/**
* 提供了开启和关闭session的方法
* @author Administrator
* @data 2018年8月1日
* @time 下午3:32:56
*/
public class SessionFactoryUtil {
//ThreadLocal为每个线程提供一个单独的存储空间
private static ThreadLocal<Session> threadLocal=new ThreadLocal<Session>();
//私有化静态变量，静态变量只实例化一次
private static SessionFactory sessionFactory;
//实例化一次sessionFactory
static {
Configuration configure = new Configuration().configure();
sessionFactory=configure.buildSessionFactory();
}
//私有化构造方法
private SessionFactoryUtil() {
}
//打开session的方法
public static Session openSession() {
//从ThreadLocal中拿取一个session
Session session = threadLocal.get();
if(null==session) {
//sessionFactory打开一个session
session=sessionFactory.openSession();
//把session又放入ThreadLocal中
threadLocal.set(session);
}
return session;
}
//关闭资源
public static void closeSession() {
//从ThreadLocal中拿取一个session
Session session = threadLocal.get();
if(null==session) {
if(session.isOpen()) {
//关闭session
session.close();
}
threadLocal.set(null);
}
}
public static void main(String[] args) {
Session session = openSession();
System.out.println(session);
System.out.println("ok");
}
}
Roles.hbm.xml：
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2018-8-7 10:53:41 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
<class name="com.liuyongqi.MavenHibernateDemo6.entity.Roles" table="roles">
<id name="rid" type="java.lang.Integer">
<column name="rid" />
<generator class="native" />
</id>
<property name="rname" type="java.lang.String">
<column name="rname" />
</property>
<set name="usersSet" table="users_roles" inverse="false">
<key column="rid"></key>
<many-to-many class="com.liuyongqi.MavenHibernateDemo6.entity.Users" column="uid"></many-to-many>
</set>
</class>
</hibernate-mapping>
Users.hbm.xml：
<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- Generated 2018-8-7 10:53:41 by Hibernate Tools 3.5.0.Final -->
<hibernate-mapping>
<class name="com.liuyongqi.MavenHibernateDemo6.entity.Users" table="users">
<id name="uid" type="java.lang.Integer">
<column name="uid" />
<generator class="native" />
</id>
<property name="uname" type="java.lang.String">
<column name="uname" />
</property>
<!-- table:指定中间表
many-to-many:指定多对多的关联关系
column:执行set集合中的持久化类在中间表的外键列的名称 -->
<set name="rolesSet" table="users_roles" inverse="true" cascade="all-delete-orphan">
<key column="uid"></key>
<many-to-many class="com.liuyongqi.MavenHibernateDemo6.entity.Roles" column="rid"></many-to-many>
</set>
</class>
</hibernate-mapping>
添加测试代码：
package test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.liuyongqi.MavenHibernateDemo6.entity.Roles;
import com.liuyongqi.MavenHibernateDemo6.entity.Users;
import com.liuyongqi.MavenHibernateDemo6.util.SessionFactoryUtil;
/**
* 添加的测试类
* @author Administrator
* @data 2018年8月7日
* @time 上午11:05:57
*/
public class TestSave {
public static void main(String[] args) {
Session session = SessionFactoryUtil.openSession();
Transaction transaction = session.beginTransaction();
Users users1=new Users("辉辉");
Users users2=new Users("静静");
Roles roles1=new Roles("老公");
Roles roles2=new Roles("老婆");
Roles roles3=new Roles("儿子");
Roles roles4=new Roles("孙子");
users1.getRolesSet().add(roles1);
users1.getRolesSet().add(roles3);
users1.getRolesSet().add(roles4);
users2.getRolesSet().add(roles2);
users2.getRolesSet().add(roles4);
roles1.getUsersSet().add(users1);
roles2.getUsersSet().add(users2);
roles3.getUsersSet().add(users1);
roles4.getUsersSet().add(users1);
roles4.getUsersSet().add(users2);
//添加
/*session.save(users1);
session.save(users2);
session.save(roles1);
session.save(roles2);
session.save(roles3);
session.save(roles4);*/
//级联添加
session.save(users1);
session.save(users2);
transaction.commit();
SessionFactoryUtil.closeSession();
}
}
控制台结果：
Hibernate:
insert
into
users
(uname)
values
(?)
Hibernate:
insert
into
roles
(rname)
values
(?)
Hibernate:
insert
into
roles
(rname)
values
(?)
Hibernate:
insert
into
roles
(rname)
values
(?)
Hibernate:
insert
into
users
(uname)
values
(?)
Hibernate:
insert
into
roles
(rname)
values
(?)
Hibernate:
insert
into
users_roles
(rid, uid)
values
(?, ?)
Hibernate:
insert
into
users_roles
(rid, uid)
values
(?, ?)
Hibernate:
insert
into
users_roles
(rid, uid)
values
(?, ?)
Hibernate:
insert
into
users_roles
(rid, uid)
values
(?, ?)
Hibernate:
insert
into
users_roles
(rid, uid)
values
(?, ?)删除的测试代码：
package test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.liuyongqi.MavenHibernateDemo6.entity.Roles;
import com.liuyongqi.MavenHibernateDemo6.entity.Users;
import com.liuyongqi.MavenHibernateDemo6.util.SessionFactoryUtil;
/**
* 删除的测试类
* @author Administrator
* @data 2018年8月7日
* @time 上午11:05:57
*/
public class TestDelete {
public static void main(String[] args) {
Session session = SessionFactoryUtil.openSession();
Transaction transaction = session.beginTransaction();
Users users = session.get(Users.class, 1);
if(users!=null) {
session.delete(users);
}
transaction.commit();
SessionFactoryUtil.closeSession();
}
}
控制台结果：
Hibernate:
select
users0_.uid as uid1_1_0_,
users0_.uname as uname2_1_0_
from
users users0_
where
users0_.uid=?
Hibernate:
select
rolesset0_.uid as uid1_2_0_,
rolesset0_.rid as rid2_2_0_,
roles1_.rid as rid1_0_1_,
roles1_.rname as rname2_0_1_
from
users_roles rolesset0_
inner join
roles roles1_
on rolesset0_.rid=roles1_.rid
where
rolesset0_.uid=?
Hibernate:
delete
from
users_roles
where
rid=?
Hibernate:
delete
from
users_roles
where
rid=?
Hibernate:
delete
from
users_roles
where
rid=?
Hibernate:
delete
from
roles
where
rid=?
Hibernate:
delete
from
roles
where
rid=?
Hibernate:
delete
from
roles
where
rid=?
Hibernate:
delete
from
users
where
uid=?修改的测试代码：
package test;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.liuyongqi.MavenHibernateDemo6.entity.Roles;
import com.liuyongqi.MavenHibernateDemo6.entity.Users;
import com.liuyongqi.MavenHibernateDemo6.util.SessionFactoryUtil;
/**
* 删除的测试类
* @author Administrator
* @data 2018年8月7日
* @time 上午11:05:57
*/
public class TestUpdate {
public static void main(String[] args) {
Session session = SessionFactoryUtil.openSession();
Transaction transaction = session.beginTransaction();
Users users = session.get(Users.class, 5);
if(users!=null) {
users.setUname("辉辉2");
session.update(users);
}
transaction.commit();
SessionFactoryUtil.closeSession();
}
}
控制台结果：
Hibernate:
select
users0_.uid as uid1_1_0_,
users0_.uname as uname2_1_0_
from
users users0_
where
users0_.uid=?
Hibernate:
update
users
set
uname=?
where
uid=?查询的测试代码：
package test;
import java.util.Set;
import org.hibernate.Session;
import org.hibernate.Transaction;
import com.liuyongqi.MavenHibernateDemo6.entity.Roles;
import com.liuyongqi.MavenHibernateDemo6.entity.Users;
import com.liuyongqi.MavenHibernateDemo6.util.SessionFactoryUtil;
/**
* 删除的测试类
* @author Administrator
* @data 2018年8月7日
* @time 上午11:05:57
*/
public class TestSelect {
public static void main(String[] args) {
Session session = SessionFactoryUtil.openSession();
Transaction transaction = session.beginTransaction();
Users users = session.get(Users.class, 1);
System.out.println(users);
Set<Roles> rolesSet = users.getRolesSet();
for (Roles roles : rolesSet) {
System.out.println(roles);
}
SessionFactoryUtil.closeSession();
}
}
控制台结果：
Hibernate:
select
users0_.uid as uid1_1_0_,
users0_.uname as uname2_1_0_
from
users users0_
where
users0_.uid=?
Hibernate:
select
rolesset0_.uid as uid1_2_0_,
rolesset0_.rid as rid2_2_0_,
roles1_.rid as rid1_0_1_,
roles1_.rname as rname2_0_1_
from
users_roles rolesset0_
inner join
roles roles1_
on rolesset0_.rid=roles1_.rid
where
rolesset0_.uid=?
Users [uid=1, uname=辉辉, rolesSet=[Roles [rid=3, rname=儿子], Roles [rid=1, rname=老公], Roles [rid=2, rname=孙子]]]
Roles [rid=3, rname=儿子]
Roles [rid=1, rname=老公]
Roles [rid=2, rname=孙子]今天的测试就到这里了，希望大家看完以后自己测试一下
如果大家想浏览我的下一篇文章，请留言
此文章属于原创，不准随意转载：https://blog.csdn.net/LYQ2332826438