多对多双向关联

一个简单示例:
一个雇员可以担任几个角色,一个角色可以拥有多个雇员,雇员和角色之间存在多对多的关联关系,
在这里我们建立多对多的双向关联...



db schema:
==============================


雇员表:

CREATE TABLE [employee] (
	[eid] [int] IDENTITY (1, 1) NOT NULL ,
	[ename] [varchar] (20) COLLATE Chinese_PRC_CI_AS NOT NULL ,
	[join_date] [datetime] NOT NULL ,
	 PRIMARY KEY  CLUSTERED 
	(
		[eid]
	)  ON [PRIMARY] 
) ON [PRIMARY]
GO



角色表:

CREATE TABLE [role] (
	[roleid] [int] IDENTITY (1, 1) NOT NULL ,
	[rolename] [varchar] (20) COLLATE Chinese_PRC_CI_AS NOT NULL ,
	 PRIMARY KEY  CLUSTERED 
	(
		[roleid]
	)  ON [PRIMARY] 
) ON [PRIMARY]
GO


雇员角色表:

CREATE TABLE [emp_role] (
	[er_id] [int] IDENTITY (1, 1) NOT NULL ,
	[er_eid] [int] NULL ,
	[er_roleid] [int] NULL ,
	 PRIMARY KEY  CLUSTERED 
	(
		[er_id]
	)  ON [PRIMARY] ,
	 FOREIGN KEY 
	(
		[er_eid]
	) REFERENCES [employee] (
		[eid]
	),
	 FOREIGN KEY 
	(
		[er_roleid]
	) REFERENCES [role] (
		[roleid]
	)
) ON [PRIMARY]
GO

Employee.java
--------------------------
package com.supersit.hibernate.bean;

import java.util.Date;
import java.util.Set;

public class Employee implements java.io.Serializable,
		com.supersit.hibernate.Interface.ObjectIn {

	/**
	 * 
	 */
	private static final long serialVersionUID = 1L;

	
	//雇员编号
	private Integer eid;

	//雇员姓名
	private String ename;

	//入职时间
	private java.util.Date join_date;

	
	//角色集合
	private java.util.Set<Role> roles = new java.util.HashSet<Role>();

	public Employee(Integer eid, String ename, Date join_date) {
		this.eid = eid;
		this.ename = ename;
		this.join_date = join_date;
	}

	public Employee(Integer eid, String ename, Date join_date, Set<Role> roles) {
		this.eid = eid;
		this.ename = ename;
		this.join_date = join_date;
		this.roles = roles;
	}

	public java.util.Set getRoles() {
		return roles;
	}

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

	public Employee() {
	}

	public Integer getEid() {
		return eid;
	}

	public void setEid(Integer eid) {
		this.eid = eid;
	}

	public String getEname() {
		return ename;
	}

	public void setEname(String ename) {
		this.ename = ename;
	}

	public java.util.Date getJoin_date() {
		return join_date;
	}

	public void setJoin_date(java.util.Date join_date) {
		this.join_date = join_date;
	}

}




Role.java
------------------------------------
package com.supersit.hibernate.bean;

import java.util.Set;

public class Role implements java.io.Serializable,
		com.supersit.hibernate.Interface.ObjectIn {

	
	//角色编号
	private Integer roleid;

	
	//角色名称
	private String rolename;

	
	//此角色下的雇员集合
	private java.util.Set emps = new java.util.HashSet();

	public Role(Integer roleid, String rolename, Set emps) {
		this.roleid = roleid;
		this.rolename = rolename;
		this.emps = emps;
	}

	public java.util.Set getEmps() {
		return emps;
	}

	public void setEmps(java.util.Set emps) {
		this.emps = emps;
	}

	public Role() {
	}

	public Integer getRoleid() {
		return roleid;
	}

	public Role(Integer roleid, String rolename) {
		this.roleid = roleid;
		this.rolename = rolename;
	}

	public void setRoleid(Integer roleid) {
		this.roleid = roleid;
	}

	public String getRolename() {
		return rolename;
	}

	public void setRolename(String rolename) {
		this.rolename = rolename;
	}

}



配置文件:

hibernate.cfg.xml
------------------------------
<?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">

<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

<session-factory>
	<property name="connection.username">sa</property>
	<property name="connection.url">
		jdbc:microsoft:sqlserver://localhost:1433;databasename=hibernate
	</property>
	<property name="dialect">
		org.hibernate.dialect.SQLServerDialect
	</property>
	<property name="connection.password">sa</property>
	<property name="connection.driver_class">
		com.microsoft.jdbc.sqlserver.SQLServerDriver
	</property>
	<property name="show_sql">true</property>
	<mapping resource="com/supersit/hibernate/mapping/Employee.hbm.xml" />
	<mapping resource="com/supersit/hibernate/mapping/Role.hbm.xml" />

</session-factory>

</hibernate-configuration>



映射文件:

Employee.hbm.xml
-----------------------------
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping package="com.supersit.hibernate.bean">
	<class name="Employee" table="employee" schema="dbo"
		catalog="hibernate">
		<id name="eid" column="eid" type="int">
			<generator class="identity"></generator>
		</id>
		<property name="ename" column="ename" type="string"
			not-null="true">
		</property>
		<property name="join_date" column="join_date" type="date"></property>

		<!-- 映射roles属性,和连接表emp_role进行关联,级联方式:保存更新,检索方式:立即检索 -->
		<set name="roles" cascade="save-update" lazy="false"
			table="emp_role">

			<!-- 连接表的字段er_eid作为外键依赖于employee表的主键eid -->
			<key column="er_eid"></key>
			<!-- many-to-many属性建立和Role的多对多关联关系,class指定关联的持久化类,连接表的字段er_roleid作为外键依赖于role表的主键roleid -->
			<many-to-many class="Role" column="er_roleid"></many-to-many>
		</set>
	</class>
</hibernate-mapping>


Role.hbm.xml
----------------------------------
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
<hibernate-mapping package="com.supersit.hibernate.bean">
	<class name="Role" table="role" catalog="hibernate" schema="dbo">
		<id name="roleid" column="roleid" type="int">
			<generator class="identity"></generator>
		</id>
		<property name="rolename" column="rolename" type="string"
			not-null="true">
		</property>

		<set name="emps" table="emp_role" cascade="save-update"
			lazy="false" >
			<key column="er_roleid"></key>
			<many-to-many class="Employee" column="er_eid"></many-to-many>
		</set>
	</class>
</hibernate-mapping>




Dao
====================================


EmployeeDao.java
----------------------------------
package com.supersit.hibernate.dao;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.Transaction;

import com.supersit.hibernate.bean.Employee;
import com.supersit.hibernate.bean.Role;
import com.supersit.hibernate.exception.HibernateMsgException;

public class EmployeeDao extends BaseDao {

	/**
	 * <p>
	 * 查询所有的雇员
	 * </p>
	 * 
	 * @author chenwei
	 * @return java.util.List
	 * @throws HibernateMsgException
	 */
	public java.util.List getEmps() throws HibernateMsgException {
		java.util.List list = new java.util.ArrayList();
		org.hibernate.Session session = null;
		org.hibernate.Transaction tran = null;
		try {
			session = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = session.beginTransaction();
			list = session.createQuery("from Employee e order by e.eid").list();

			tran.commit();
		} catch (Exception e) {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(session);
		}
		return list;
	}

	/**
	 * <p>
	 * 更改指定用户的角色
	 * </p>
	 * 
	 * @author chenwei
	 * @param eid:用户ID
	 * @param roleids:角色ID数组
	 * 
	 */
	public static void opeRolesOfEmp(Integer eid, String[] roleids)
			throws HibernateMsgException {
		org.hibernate.Session session = null;
		org.hibernate.Transaction tran = null;
		try {
			session = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = session.beginTransaction();
			Employee emp = (Employee) session.load(Employee.class, eid);
			java.util.Set roles = new java.util.HashSet();
			for (int i = 0; i < roleids.length; i++) {

				// 查询角色(此处应传入一个Session对象,否则会抛出org.hibernate.NonUniqueObjectException)
				Role role = new RoleDao().getRoleById(session, new Integer(
						roleids[i]));
				System.out.println("rolename=" + role.getRolename());
				roles.add(role);
			}
			emp.setRoles(roles);
			session.saveOrUpdate(emp);
			tran.commit();
		} catch (Exception e) {
			e.printStackTrace();
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(session);
		}
	}

	public Employee initEmp(Employee emp) throws HibernateMsgException {
		Session session = null;
		Transaction tran = null;
		try {
			session = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = session.beginTransaction();
			org.hibernate.Hibernate.initialize(emp.getRoles());
			session.update(emp);
			tran.commit();
		} catch (Exception e) {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(session);
		}
		return emp;
	}

	public static void main(String[] args) throws HibernateMsgException {
		// select();
		opeRolesOfEmp(new Integer(1), new String[] { "1", "3", "4" });
	}

	// 检索
	public static void select() throws HibernateMsgException {

		EmployeeDao dao = new EmployeeDao();
		List list = dao.getEmps();
		for (int i = 0; i < list.size(); i++) {
			Employee emp = (Employee) list.get(i);
			System.out.println("eid=" + emp.getEid());
			System.out.println("ename=" + emp.getEname());
			System.out.println("join_date=" + emp.getJoin_date()); //
			// 映射roles属性,lazy=false时，可以立即检索
			Set roles = emp.getRoles();
			java.util.Iterator ite = roles.iterator();
			while (ite.hasNext()) {
				Role role = (Role) ite.next();
				System.out.println("rolename=" + role.getRolename());
			}
			System.out.println("===========================================");
		}

	}

	// 保存对象
	public static void insert() throws HibernateMsgException {

		java.util.Date date = new java.util.Date();
		java.text.SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
		try {
			date = format.parse("2007-10-17");
		} catch (ParseException e) {
			e.printStackTrace();
		}

		Employee emp = new Employee(new Integer(1), "张信哲", date);

		Session session = null;
		Transaction tran = null;
		try {
			session = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = session.beginTransaction();
			boolean b = new EmployeeDao().saveObj(session, emp);
			if (b) {
				System.out.println("成功保存一个Employee对象");
			}
			tran.commit();
		} catch (Exception e) {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(session);
		}

	}

}



RoleDao.java
------------------------
package com.supersit.hibernate.dao;

import org.hibernate.Session;
import org.hibernate.Transaction;

import com.supersit.hibernate.bean.Employee;
import com.supersit.hibernate.bean.Role;
import com.supersit.hibernate.exception.HibernateMsgException;

public class RoleDao extends BaseDao {

	/**
	 * <p>
	 * 根据角色ID查找角色(传入一个Session对象)
	 * </p>
	 * 
	 * @param roleid:角色ID
	 * @return com.supersit.hibernate.bean.Role
	 * @throws HibernateMsgException
	 */
	public com.supersit.hibernate.bean.Role getRoleById(Session session,
			Integer roleid) throws HibernateMsgException {
		Role role = new Role();
		try {
			java.util.List list = session.createQuery(
					"from Role r where r.roleid=:id").setInteger("id", roleid)
					.list();
			if (list != null && list.size() > 0)
				role = (Role) list.get(0);

		} catch (Exception e) {

		}
		return role;
	}

	/**
	 * <p>
	 * 根据角色ID查找角色(创建一个新的Session)
	 * </p>
	 * 
	 * @param roleid:角色ID
	 * @return com.supersit.hibernate.bean.Role
	 * @throws HibernateMsgException
	 */
	public com.supersit.hibernate.bean.Role getRoleById(Integer roleid)
			throws HibernateMsgException {
		Role role = new Role();
		Session session = null;
		Transaction tran = null;
		try {
			session = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = session.beginTransaction();
			java.util.List list = session.createQuery(
					"from Role r where r.roleid=:id").setInteger("id", roleid)
					.list();
			if (list != null && list.size() > 0)
				role = (Role) list.get(0);
			tran.commit();
		} catch (Exception e) {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(session);
		}
		return role;
	}

	public static void main(String[] args) throws HibernateMsgException {
		selectEmpsOfEachRole();
	}

	/**
	 * <p>
	 * 查询所有的角色
	 * </p>
	 * 
	 * @param session
	 * @return java.util.List
	 */
	public static java.util.List getAllRoles(org.hibernate.Session session) {
		java.util.List list = new java.util.ArrayList();
		list = session.createQuery("from Role r order by r.roleid asc").list();
		return list;
	}

	public static void selectEmpsOfEachRole() throws HibernateMsgException {
		org.hibernate.Session session = null;
		org.hibernate.Transaction tran = null;
		try {
			session = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = session.beginTransaction();
			java.util.List list = getAllRoles(session);

			for (int i = 0; i < list.size(); i++) {
				Role role = (Role) list.get(i);
				System.out.println("角色编号:" + role.getRoleid());
				System.out.println("角色名称:" + role.getRolename());
				System.out.println("此角色下的所有雇员>>>");
				java.util.Iterator ite = role.getEmps().iterator();
				while (ite.hasNext()) {
					Employee emp = (Employee) ite.next();
					System.out.println("雇员编号:" + emp.getEid());
					System.out.println("雇员姓名:" + emp.getEname());
					System.out.println("入职时间:" + emp.getJoin_date());
				}
				System.out
						.println("=======================================================");
			}
			tran.commit();

		} catch (Exception e) {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(session);
		}
	}

}








/**
 * 
 * <p>
 * 对于持久化类的添加,删除,修改可以通过继承这个类来实现 如果已开启Session缓存,可以传入这个Session对象进行相应的操作,当然也可以
 * 不调用此方法,直接调用Session对象相应的方法即可,在这里只是想实现面向接口编程
 * 对于没有开启Session缓存的情况,直接调用只有一个参数的方法,在方法体中会自动创建 Session对象,进行相关操作...
 * </p>
 * 
 * @author chenwei
 * 2007-10-26
 * 
 */
BaseDao.java
----------------------------
package com.supersit.hibernate.dao;

import org.hibernate.Session;

import com.supersit.hibernate.exception.HibernateMsgException;

public class BaseDao {

	/**
	 * <p>
	 * 保存一个com.supersit.hibernate.Interface.ObjectIn对象
	 * </p>
	 * 
	 * @author chenwei
	 * @param com.supersit.hibernate.Interface.ObjectIn
	 * @return boolean
	 * @throws HibernateMsgException
	 */
	public boolean saveObj(com.supersit.hibernate.Interface.ObjectIn in)
			throws HibernateMsgException {

		org.hibernate.Session ses = null;
		org.hibernate.Transaction tran = null;
		boolean flag = true;
		try {
			ses = com.supersit.hibernate.factory.HibernateSessionFactory1
					.getSession();
			tran = ses.beginTransaction();
			ses.save(in);
			tran.commit();
		} catch (Exception e) {
			e.printStackTrace();
			flag = false;
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(ses);
		}
		return flag;
	}

	/**
	 * <p>
	 * 保存一个com.supersit.hibernate.Interface.ObjectIn对象
	 * </p>
	 * 
	 * @author chenwei
	 * @param com.supersit.hibernate.Interface.ObjectIn
	 * @return boolean
	 * @throws HibernateMsgException
	 */
	public boolean saveObj(Session session,
			com.supersit.hibernate.Interface.ObjectIn in) {
		boolean flag = true;
		try {
			session.save(in);
		} catch (Exception e) {
			e.printStackTrace();
			flag = false;
		}
		return flag;
	}

	/**
	 * <p>
	 * 修改一个com.supersit.hibernate.Interface.ObjectIn对象
	 * </p>
	 * 
	 * @author chenwei
	 * @param com.supersit.hibernate.Interface.ObjectIn
	 * @return boolean
	 * @throws HibernateMsgException
	 */
	public boolean updateObj(com.supersit.hibernate.Interface.ObjectIn in)
			throws HibernateMsgException {
		boolean flag = true;
		org.hibernate.Session ses = null;
		org.hibernate.Transaction tran = null;
		try {
			ses = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = ses.beginTransaction();
			ses.update(in);
			tran.commit();
		} catch (Exception e) {
			flag = false;
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(ses);
		}
		return flag;
	}

	/**
	 * <p>
	 * 修改一个com.supersit.hibernate.Interface.ObjectIn对象
	 * </p>
	 * 
	 * @author chenwei
	 * @param com.supersit.hibernate.Interface.ObjectIn
	 * @return boolean
	 * @throws HibernateMsgException
	 */
	public boolean updateObj(Session session,
			com.supersit.hibernate.Interface.ObjectIn in) {
		boolean flag = true;
		try {
			session.update(in);
		} catch (Exception e) {
			flag = false;
		}
		return flag;
	}

	/**
	 * <p>
	 * 删除一个com.supersit.hibernate.Interface.ObjectIn对象
	 * </p>
	 * 
	 * @author chenwei
	 * @param com.supersit.hibernate.Interface.ObjectIn
	 * @return boolean
	 * @throws HibernateMsgException
	 */

	public boolean deleteObj(com.supersit.hibernate.Interface.ObjectIn in)
			throws HibernateMsgException {
		boolean flag = true;
		org.hibernate.Session session = null;
		org.hibernate.Transaction tran = null;
		try {
			session = com.supersit.hibernate.factory.HibernateSessionFactory
					.getSession();
			tran = session.beginTransaction();
			session.delete(in);
			tran.commit();
		} catch (Exception e) {
			flag = false;
			com.supersit.hibernate.factory.HibernateSessionFactory
					.rollbackTran(tran);
		} finally {
			com.supersit.hibernate.factory.HibernateSessionFactory
					.closeSession(session);
		}
		return flag;
	}

	/**
	 * <p>
	 * 删除一个com.supersit.hibernate.Interface.ObjectIn对象
	 * </p>
	 * 
	 * @author chenwei
	 * @param com.supersit.hibernate.Interface.ObjectIn
	 * @return boolean
	 * @throws HibernateMsgException
	 */

	public boolean deleteObj(Session session,
			com.supersit.hibernate.Interface.ObjectIn in) {
		boolean flag = true;
		try {
			session.delete(in);
		} catch (Exception e) {
			flag = false;
		}
		return flag;
	}
}



ObjectIn.java
------------------------------

package com.supersit.hibernate.Interface;

public interface ObjectIn {

}