例子
查询年龄在20-30岁之间的所有学生对象
List list = session.createCriteria(Student.class)
      .add(Restrictions.between("age",new Integer(20),new Integer(30)).list();
查询学生姓名在AAA,BBB,CCC之间的学生对象
String[] names = {"AAA","BBB","CCC"};
List list = session.createCriteria(Student.class)
      .add(Restrictions.in("name",names)).list();
查询年龄为空的学生对象
List list = session.createCriteria(Student.class)
      .add(Restrictions.isNull("age")).list();
查询年龄等于20或者年龄为空的学生对象
List list = session.createCriteria(Student.class)
      .add(Restrictions.or(Restrictions.eq("age",new Integer(20)),
                 Restrictions.isNull("age")).list();
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使用QBC实现动态查询 
public List findStudents(String name,int age){
 Criteria criteria = session.createCriteria(Student.class);
 if(name != null){
  criteria.add(Restrictions.liek("name",name,MatchMode.ANYWHERE));
 }
 if(age != 0){
  criteria.add(Restrictions.eq("age",new Integer(age)));
 }
 criteria.addOrder(Order.asc("name"));//根据名字升序排列
 return criteria.list();
}
 
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今天用了写hibernate高级查询时用了Restrictions(当然Expression也是可以以的)这个类.感觉不错.
下面的代码写的不易读.其实核心就是一句
Restrictions.or(Restrictions.like(),Restrictions.or(Restrictions.like,........))
里面的or可以无限加的.还是比较好用

Session session = getHibernateTemplate().getSessionFactory()
                .openSession();
        Criteria criteria = session.createCriteria(Film.class);
        List<Film> list = criteria.add(
            Restrictions.or(Restrictions.like("description", key,MatchMode.ANYWHERE),
            Restrictions.or(Restrictions.like("name", key,MatchMode.ANYWHERE),
                Restrictions.or(    Restrictions.like("direct", key,MatchMode.ANYWHERE),
                Restrictions.or(Restrictions.like("mainplay",key,MatchMode.ANYWHERE),
                        Restrictions.like("filearea", key,MatchMode.ANYWHERE)))))).list();

        session.close();
        return list;