hibernate——hql总结

1. 查询整个映射对象所有字段?

Java代码

1. //直接from查询出来的是一个映射对象，即：查询整个映射对象所有字段?????
2. ????????String?hql?=?"from?Users";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ?????????????
5. ????????List<Users>?users?=?query.list();?????
6. ????????for(Users?user?:?users){?????
7. ????????????System.out.println(user.getName()?+?"?:?"?+?user.getPasswd()?+?"?:?"?+?user.getId());?????
8. ????????}?????
9. ????
10. ?输出结果为：?????
11. name1?:?password1?:?1????
12. name2?:?password2?:?2????
13. name3?:?password3?:?3????

2.查询单个字段??

Java代码?

1. //查询单个字段?????
2. ????????String?hql?=?"?select?name?from?Users";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ?????????????
5. ????????List<String>?list?=?query.list();?????
6. ????????for(String?str?:?list){?????
7. ????????????System.out.println(str);?????
8. ????????}?????
9. 输出结果为：?????
10. name1?????
11. name2?????
12. name3????

3.查询其中几个字段?

1. //查询其中几个字段?????
2. ????????String?hql?=?"?select?name,passwd?from?Users";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ????????//默认查询出来的list里存放的是一个Object数组?????
5. ????????List<Object[]>?list?=?query.list();?????
6. ????????for(Object[]?object?:?list){?????
7. ????????????String?name?=?(String)object[0];?????
8. ????????????String?passwd?=?(String)object[1];?????
9. ?????????????????
10. ????????????System.out.println(name?+?"?:?"?+?passwd);?????
11. ????????}?????
12. 输出结果为：?????
13. name1?:?password1?????
14. name2?:?password2?????
15. name3?:?password3????

4.修改默认查询结果(query.list())不以Object[]数组形式返回，以List形式返回?
引用

//查询其中几个字段,添加new list(),注意list里的l是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是List集合了???
??????? String hql = " select new list(name,passwd) from Users";???
??????? Query query = session.createQuery(hql);???
??????? //默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是List集合了???
??????? List<List> list = query.list();???
??????? for(List user : list){???
??????????? String name = (String)user.get(0);???
??????????? String passwd = (String)user.get(1);???
???????????????
??????????? System.out.println(name + " : " + passwd);???
??????? }???
??????? /**??
??????? 输出结果为：??
???????? name1 : password1??
??????? name2 : password2??
??????? name3 : password3??
???????? */?

5.修改默认查询结果(query.list())不以Object[]数组形式返回，以Map形式返回?

1. //查询其中几个字段,添加new?map(),注意map里的m是小写的。也不需要导入包，这样通过query.list()出来的list里存放的不再是默认的Object数组了，而是map集合了?????
2. ????????String?hql?=?"?select?new?map(name,passwd)?from?Users";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ????????//默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是Map集合了?????
5. ????????List<Map>?list?=?query.list();?????
6. ????????for(Map?user?:?list){?????
7. ????????????//一条记录里所有的字段值都是map里的一个元素,key是字符串0,1,2,3....，value是字段值?????
8. ????????????//如果将hql改为：String?hql?=?"?select?new?map(name?as?username,passwd?as?password)?from?Users";,那么key将不是字符串0,1,2...了，而是"username","password"了?????
9. ????????????String?name?=?(String)user.get("0");//get("0");是get(key),注意:0,1,2...是字符串，而不是整形?????
10. ????????????String?passwd?=?(String)user.get("1");?????
11. ?????????????????
12. ????????????System.out.println(name?+?"?:?"?+?passwd);?????
13. ????????}?????
14. ????????/**???
15. ????????输出结果为：???
16. ?????????name1?:?password1???
17. ????????name2?:?password2???
18. ????????name3?:?password3???
19. ?????????*/????

6.修改默认查询结果(query.list())不以Object[]数组形式返回，以Set形式返回,但是因为Set里是不允许有重复的元素，所以:username和password的值不能相同。只需将hql改为：String hql = " select new set(name,passwd) from Users";?

7.修改默认查询结果(query.list())不以Object[]数组形式返回，以自定义类型返回?
自定义类：?

?

1. package?com.domain;?????
2. ????
3. public?class?MyUser?{?????
4. ????
5. ????private?String?username;?????
6. ????private?String?password;?????
7. //因为：String?hql?=?"?select?new??com.domain.MyUser(name,passwd)?from?Users";所以必须要有接受2个参数的构造函数?????
8. ????public?MyUser(String?username,String?password){?????
9. ????????this.username?=?username;?????
10. ????????this.password?=?password;?????
11. ????}?????
12. ?????????
13. ????public?String?getUsername()?{?????
14. ????????return?username;?????
15. ????}?????
16. ????public?void?setUsername(String?username)?{?????
17. ????????this.username?=?username;?????
18. ????}?????
19. ????public?String?getPassword()?{?????
20. ????????return?password;?????
21. ????}?????
22. ????public?void?setPassword(String?password)?{?????
23. ????????this.password?=?password;?????
24. ????}?????
25. ?????????
26. ?????????
27. }????

?

1. //通过query.list()出来的list里存放的不再是默认的Object数组了,而是自定义的类MyUser,必须加包名，String?hql?=?"from?Users";中的Users类也是必须加包名的，但是因为再Users.hbm.xml里<hibernate-mapping?auto-import="true">?auto-import默认值为true（所以auto-import属性也可以不写）,自动导入了?????
2. ????????String?hql?=?"?select?new??com.domain.MyUser(name,passwd)?from?Users";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ????????//默认查询出来的list里存放的是一个Object数组，但是在这里list里存放的不再是默认的Object数组了，而是MyUser对象了?????
5. ????????List<MyUser>?myUsers?=?query.list();?????
6. ????????for(MyUser?myUser?:?myUsers){?????
7. ????????????String?name?=?myUser.getUsername();?????
8. ????????????String?passwd?=?myUser.getPassword();?????
9. ????????????System.out.println(name?+?"?:?"?+?passwd);?????
10. ????????}?????
11. ????????/**???
12. ????????输出结果为：???
13. ????????name1?:?password1???
14. ????????name2?:?password2???
15. ????????name3?:?password3???
16. ?????????*/? ??

8：条件查询?

?

1. //条件查询，参数索引值从0开始，索引位置。通过setString,setParameter设置参数?????
2. ????????String?hql?=?"from?Users?where?name=??and?passwd=?";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ????????//第1种方式?????
5. //??????query.setString(0,?"name1");?????
6. //??????query.setString(1,?"password1");?????
7. ????????//第2种方式?????
8. ????????query.setParameter(0,?"name1",Hibernate.STRING);?????
9. ????????query.setParameter(1,?"password1",Hibernate.STRING);?????
10. ????????List<Users>?list?=?query.list();?????
11. ????????for(Users?users?:?list){?????
12. ????????????System.out.println(users.getId());?????
13. ????????}?????

?

1. //条件查询，自定义索引名(参数名):username,:password.通过setString,setParameter设置参数?????
2. ????????String?hql?=?"from?Users?where?name=:username?and?passwd=:password";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ????????//第1种方式?????
5. //??????query.setString("username",?"name1");?????
6. //??????query.setString("password",?"password1");?????
7. ????????//第2种方式,第3个参数确定类型?????
8. ????????query.setParameter("username",?"name1",Hibernate.STRING);?????
9. ????????query.setParameter("password",?"password1",Hibernate.STRING);?????
10. ????????List<Users>?list?=?query.list();?????
11. ????????for(Users?users?:?list){?????
12. ????????????System.out.println(users.getId());?????
13. ????????}????

?

1. //条件查询,通过setProperties设置参数?????
2. ????????String?hql?=?"from?Users?where?name=:username?and?passwd=:password";?????
3. ????????Query?query?=?session.createQuery(hql);?????
4. ????????//MyUser类的2个属性必须和:username和:password对应?????
5. ????????MyUser?myUser?=?new?MyUser("name1","password1");?????
6. ????????query.setProperties(myUser);?????
7. ????????List<Users>?list?=?query.list();?????
8. ????????for(Users?users?:?list){?????
9. ????????????System.out.println(users.getId());?????
10. ????????} ?