Hibernate学习35 -- Hibernate查询语言（HQL）9 -- 连接查询

连接查询：

    * 内连

    * 外连接（左连接/右连接）

例子代码如下：

/**  * 连接查询  */ public class JoinQueryTest extends TestCase {     public void testQuery1() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();                   //List students = session.createQuery("select c.name, s.name from Student s join s.classes c").list();            List students = session.createQuery ("select c.name, s.name from Student s inner join s.classes c") .list();            for (Iterator iter=students.iterator(); iter.hasNext();) {               Object[] obj = (Object[])iter.next();               System.out.println(obj[0] + "," + obj[1]);            }            session.getTransaction().commit();        }catch(Exception e) {            e.printStackTrace();            session.getTransaction().rollback();        }finally {            HibernateUtils.closeSession(session);        }     }     public void testQuery2() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();              List students = session.createQuery ("select c.name, s.name from Classes c left join c.students s").list();            for (Iterator iter=students.iterator(); iter.hasNext();) {               Object[] obj = (Object[])iter.next();               System.out.println(obj[0] + "," + obj[1]);            }            session.getTransaction().commit();        }catch(Exception e) {            e.printStackTrace();            session.getTransaction().rollback();        }finally {            HibernateUtils.closeSession(session);        }     }       public void testQuery3() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();            List students = session.createQuery ("select c.name, s.name from Classes c right join c.students s").list();            for (Iterator iter=students.iterator(); iter.hasNext();) {               Object[] obj = (Object[])iter.next();               System.out.println(obj[0] + "," + obj[1]);            }            session.getTransaction().commit();        }catch(Exception e) {            e.printStackTrace();            session.getTransaction().rollback();        }finally {            HibernateUtils.closeSession(session);        }     }   }