Criteria criteria = session.createCriteria(User.class);
criteria.addOrder(Order.asc("age"));
List users = criteria.list();
setMaxResults()方法可以限定查询回来的笔数,如果配合setFirstResult()设定传回查询结果第一笔数据的位置,就可以实现简单的分页,例如传回第51笔之后的50笔数据(如果有的话): Criteria criteria = session.createCriteria(User.class); criteria.setFirstResult(51); criteria.setMaxResult(50); List users = criteria.list();您可以对查询结果进行统计动作,使用Projections的avg()、rowCount()、count()、max()、min()、countDistinct()等方法,例如对查询结果的"age"作平均:
Criteria criteria = session.createCriteria(User.class);
criteria.setProjection(Projections.avg("age"));
List users = criteria.list();
Iterator iterator = users.iterator();
while(iterator.hasNext()) {
System.out.println(iterator.next());
}
还可以配合Projections的groupProperty()来对结果进行分组,例如以"age"进行分组,也就是如果数据中"age"如果有20、20、25、30,则以下会显示20、25、30:Criteria criteria = session.createCriteria(User.class);
criteria.setProjection(Projections.groupProperty("age"));
List users = criteria.list();
Iterator iterator = users.iterator();
while(iterator.hasNext()) {
System.out.println(iterator.next());
}
ProjectionList projectionList = Projections.projectionList();
projectionList.add(Projections.groupProperty("age"));
projectionList.add(Projections.rowCount());
Criteria criteria = session.createCriteria(User.class);
criteria.setProjection(projectionList);
List users = criteria.list();
Iterator iterator = users.iterator();
while(iterator.hasNext()) {
Object[] o = (Object[]) iterator.next();
System.out.println(o[0] + "\t" + o[1]);
}
如果有一个已知的对象,则可以根据这个对象作为查询的依据,看看是否有属性与之类似的对象,例如:User user = new User();
user.setAge(new Integer(30));
Criteria criteria = session.createCriteria(User.class);
criteria.add(Example.create(user));
List users = criteria.list();
Iterator iterator = users.iterator();
System.out.println("id \t name/age");
while(iterator.hasNext()) {
User ur = (User) iterator.next();
System.out.println(ur.getId() +" \t " + ur.getName() +"/" +ur.getAge());
}
在这个例子中,user对象中有已知的属性"age"为30,使用Example会自动过滤掉user的空属性,并以之作为查询的依据,也就是找出"age"同为30的数据。Criteria roomCriteria = session.createCriteria(Room.class);
Criteria userCriteria = roomCriteria.createCriteria("users");
userCriteria.add(Restrictions.eq("age", new Integer(30)));
List rooms = roomCriteria.list(); // 只列出users属性中有user之"age"为30的Room
Iterator iterator = rooms.iterator();