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);
    }
  }   
  
}