hibernate学习6之many-to-many单向关联

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<!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="hibernate.connection.url">jdbc:mysql://localhost/hibernate_many2many</property><property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property><property name="hibernate.connection.username">root</property><property name="hibernate.connection.password">bjsxt</property><property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property><property name="hibernate.show_sql">true</property><mapping resource="com/bjsxt/hibernate/User.hbm.xml"/><mapping resource="com/bjsxt/hibernate/Role.hbm.xml"/></session-factory></hibernate-configuration>

public class Role {private int id;private String name;//setter，getter}

import java.util.Set;public class User {private int id;private String name;private Set roles; //一个用户有多个角色//setter，getter}

Role.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"><hibernate-mapping><class name="com.bjsxt.hibernate.Role" table="t_role"><id name="id"><generator class="native"/></id><property name="name"/></class></hibernate-mapping>

User.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"><hibernate-mapping><class name="com.bjsxt.hibernate.User" table="t_user"><id name="id"><generator class="native"/></id><property name="name"/><set name="roles" table="t_user_role"><key column="userid"/><many-to-many class="com.bjsxt.hibernate.Role" column="roleid"/></set></class></hibernate-mapping>

上面的配置要注意：t_user_role是生成的第三方表，它同时维护着User表和Role表的关系。
它是通过2个字段(column="userid"和column="roleid")维护着User表和Role表的关系。

测试一下：

import java.util.HashSet;import java.util.Iterator;import java.util.Set;import org.hibernate.Session;import junit.framework.TestCase;public class Many2Many extends TestCase {public void testSave2() {Session session = null;try {session = HibernateUtils.getSession();session.beginTransaction();Role r1 = new Role();r1.setName("数据录入人员");session.save(r1);Role r2 = new Role();r2.setName("商务主管");session.save(r2);Role r3 = new Role();r3.setName("大区经理");session.save(r3);User u1 = new User();u1.setName("10");Set u1Roles = new HashSet();u1Roles.add(r1);u1Roles.add(r2);u1.setRoles(u1Roles);User u2 = new User();u2.setName("祖儿");Set u2Roles = new HashSet();u2Roles.add(r2);u2Roles.add(r3);u2.setRoles(u2Roles);User u3 = new User();u3.setName("杰伦");Set u3Roles = new HashSet();u3Roles.add(r1);u3Roles.add(r2);u3Roles.add(r3);u3.setRoles(u3Roles);session.save(u1);session.save(u2);session.save(u3);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();User user = (User)session.load(User.class, 1);System.out.println(user.getName());for (Iterator iter=user.getRoles().iterator(); iter.hasNext();) {Role role = (Role)iter.next();System.out.println(role.getName());}session.getTransaction().commit();}catch(Exception e) {e.printStackTrace();session.getTransaction().rollback();}finally {HibernateUtils.closeSession(session);}}}

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