hibernate学习7之many-to-many双向关联

Hibernate.cfg.xml配置同前一节。

import java.util.Set;
public class User {
  private int id;
  private String name;
  private Set roles; 
  //setter，getter
}

import java.util.Set;
public class Role { 
  private int id; 
  private String name;  
  private Set users;
  //setter，getter
}

User.hbm.xml中这样配置：

<?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>

Role.hbm.xml中这样配置：

<?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"/>
    <set name="users" table="t_user_role" order-by="userid">
      <key column="roleid"/>
      <many-to-many class="com.bjsxt.hibernate.User" column="userid"/>
    </set>
  </class>
</hibernate-mapping>

比较上面2个配置，其实userid和roleid互换位置而已；

这里order-by="userid"是查出来的数据根据userid排序，去掉也没关系。

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);
    }
  }   
  
  public void testLoad2() {
    Session session = null;
    try {
      session = HibernateUtils.getSession();
      session.beginTransaction();
      Role role = (Role)session.load(Role.class, 1);
      System.out.println(role.getName());
      for (Iterator iter=role.getUsers().iterator(); iter.hasNext();) {
        User user = (User)iter.next();
        System.out.println(user.getName());
      }
      session.getTransaction().commit();
    }catch(Exception e) {
      e.printStackTrace();
      session.getTransaction().rollback();
    }finally {
      HibernateUtils.closeSession(session);
    }
  }   
  
}