hibernate------hql总结[转]
1. 查询整个映射对象所有字段
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//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
String hql = "from Users";
Query query = session.createQuery(hql);
List<Users> users = query.list();
for(Users user : users){
System.out.println(user.getName() + " : " + user.getPasswd() + " : " + user.getId());
}
输出结果为:
name1 : password1 : 1
name2 : password2 : 2
name3 : password3 : 3
2.查询单个字段
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//查询单个字段
String hql = " select name from Users";
Query query = session.createQuery(hql);
List<String> list = query.list();
for(String str : list){
System.out.println(str);
}
输出结果为:
name1
name2
name3
3.查询其中几个字段
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//查询其中几个字段
String hql = " select 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
List<Object[]> list = query.list();
for(Object[] object : list){
String name = (String)object[0];
String passwd = (String)object[1];
System.out.println(name + " : " + passwd);
}
输出结果为:
name1 : password1
name2 : password2
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
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//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
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//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
String hql = " select new map(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Map集合了
List<Map> list = query.list();
for(Map user : list){
//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
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//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
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String name = (String)user.get("0");//get("0");是get(key),注意:0,1,2
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String passwd = (String)user.get("1");
System.out.println(name + " : " + passwd);
}
/**
输出结果为:
name1 : password1
name2 : password2
name3 : password3
*/
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:
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package com.domain;
public class MyUser {
private String username;
private String password;
//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
public MyUser(String username,String password){
this.username = username;
this.password = password;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
//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
String hql = " select new com.domain.MyUser(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MyUser对象了
List<MyUser> myUsers = query.list();
for(MyUser myUser : myUsers){
String name = myUser.getUsername();
String passwd = myUser.getPassword();
System.out.println(name + " : " + passwd);
}
/**
输出结果为:
name1 : password1
name2 : password2
name3 : password3
*/
8:条件查询
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//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
String hql = "from Users where name=? and passwd=?";
Query query = session.createQuery(hql);
//第1种方式
// query.setString(0, "name1");
// query.setString(1, "password1");
//第2种方式
query.setParameter(0, "name1",Hibernate.STRING);
query.setParameter(1, "password1",Hibernate.STRING);
List<Users> list = query.list();
for(Users users : list){
System.out.println(users.getId());
}
//条件查询,自定义索引名(参数名):username,:password.通过setString,setParameter设置参数
String hql = "from Users where name=:username and passwd=:password";
Query query = session.createQuery(hql);
//第1种方式
// query.setString("username", "name1");
// query.setString("password", "password1");
//第2种方式,第3个参数确定类型
query.setParameter("username", "name1",Hibernate.STRING);
query.setParameter("password", "password1",Hibernate.STRING);
List<Users> list = query.list();
for(Users users : list){
System.out.println(users.getId());
}
//条件查询,通过setProperties设置参数
String hql = "from Users where name=:username and passwd=:password";
Query query = session.createQuery(hql);
//MyUser类的2个属性必须和:username和:password对应
MyUser myUser = new MyUser("name1","password1");
query.setProperties(myUser);
List<Users> list = query.list();
for(Users users : list){
System.out.println(users.getId());
}