1: QBE (Query By Example)   Criteria cri = session.createCriteria(Student.class);   cri.add(Example.create(s)); //s是一个Student对象   list cri.list();      实质：创建一个模版，比如我有一个表serial有一个 giftortoy字段，我设置serial.setgifttoy("2"),         则这个表中的所有的giftortoy为2的数据都会出来2: QBC (Query By Criteria) 主要有Criteria,Criterion,Oder,Restrictions类组成   session = this.getSession();   Criteria cri = session.createCriteria(JdItemSerialnumber.class);   Criterion cron = Restrictions.like("customer",name);   cri.add(cron);   list = cri.list();   ==============================   比较运算符   HQL运算符                   QBC运算符                      含义      =                     Restrictions.eq()                  等于      <>                   Restrictions.not(Exprission.eq())  不等于      >                     Restrictions.gt()                  大于      >=                   Restrictions.ge()                  大于等于      <                     Restrictions.lt()                  小于      <=                   Restrictions.le()                  小于等于      is null             Restrictions.isnull()              等于空值      is not null      Restrictions.isNotNull()           非空值      like                 Restrictions.like()                字符串模式匹配      and                Restrictions.and()                 逻辑与      and                Restrictions.conjunction()         逻辑与      or                   Restrictions.or()                  逻辑或      or                   Restrictions.disjunction()         逻辑或      not                  Restrictions.not()                 逻辑非      in(列表)          Restrictions.in()                  等于列表中的某一个值      ont in(列表)         Restrictions.not(Restrictions.in())不等于列表中任意一个值      between x and y      Restrictions.between()             闭区间xy中的任意值      not between x and y  Restrictions.not(Restrictions..between()) 小于值X或者大于值y3: HQL   String hql = "select s.name ,avg(s.age) from Student s group by s.name";   Query query = session.createQuery(hql);   list = query.list();   ....4: 本地SQL查询   session = sessionFactory.openSession();   tran = session.beginTransaction();   SQLQuery sq = session.createSQLQuery(sql);   sq.addEntity(Student.class);   list = sq.list();   tran.commit();5: QID    Session的get()和load()方法提供了根据对象ID来检索对象的方式。该方式被用于事先知道了要检索对象ID的情况。