Hibernate学习28 -- Hibernate查询语言（HQL）2 -- 简单属性查询

简单属性查询：

* 单一属性查询，返回结果集属性列表，元素类型和实体类中相应的属性类型一致

* 多个属性查询,返回的集合元素是对象数组,数组元素的类型和对应的属性在实体类中的类型一致

  数组的长度取决与select中属性的个数

* 如果认为返回数组不够对象化，可以采用hql动态实例化Student对象。

例子代码如下：

/**  * 简单属性查询  * @author Administrator  */ public class SimplePropertyQueryTest extends TestCase {         /**      * 单一属性查询      */     public void testQuery1() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();                       //返回结果集属性列表，元素类型和实体类中相应的属性类型一致            List students = session.createQuery ("select name from Student").list();            for (Iterator iter=students.iterator(); iter.hasNext();) {               String name = (String)iter.next();               System.out.println(name);            }            session.getTransaction().commit();        }catch(Exception e) {            e.printStackTrace();            session.getTransaction().rollback();        }finally {            HibernateUtils.closeSession(session);        }     }     /**      * 多个属性查询      */     public void testQuery2() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();                   //查询多个属性，其集合元素是对象数组            //数组元素的类型和对应的属性在实体类中的类型一致            //数组的长度取决与select中属性的个数            List students = session.createQuery ("select id, name from Student").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);        }     }     /**      * 多个属性查询      */     public void testQuery3() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();                       //查询多个属性，其集合元素是List            //数组元素的类型和对应的属性在实体类中的类型一致            //List的长度取决与select中属性的个数            List students = session.createQuery ("select new list(id, name) from Student").list();            for (Iterator iter=students.iterator(); iter.hasNext();) {               List obj = (List)iter.next();               System.out.println(obj.get(0) + "," + obj.get(1));            }            session.getTransaction().commit();        }catch(Exception e) {            e.printStackTrace();            session.getTransaction().rollback();        }finally {            HibernateUtils.closeSession(session);        }     }     /**      * 返回Student实体对象      */     public void testQuery4() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();                   //如果认为返回数组不够对象化，可以采用hql动态实例化Student对象            //此时list中为Student对象集合            List students = session.createQuery ("select new Student(id, name) from Student").list();            for (Iterator iter=students.iterator(); iter.hasNext();) {               Student student = (Student)iter.next();               System.out.println(student.getId() + "," + student.getName());            }            session.getTransaction().commit();        }catch(Exception e) {            e.printStackTrace();            session.getTransaction().rollback();        }finally {            HibernateUtils.closeSession(session);        }     }     /**      * 使用别名      */     public void testQuery5() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();                   //可以使用别名            List students = session.createQuery ("select s.id, s.name from Student 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);        }     }     /**      * 使用别名      */     public void testQuery6() {        Session session = null;        try {            session = HibernateUtils.getSession();            session.beginTransaction();                       //可以使用as命名别名            List students = session.createQuery ("select s.id, s.name from Student as 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);        }     } }