hibernate学习6之many-to-many单向关联

<!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);
}
}

}