hibernate HQL演示:
HQL是面向对象的,里面的参数都是对象名和对象的属性名不要填写标的列名.
package test;
import java.util.Arrays;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
import org.hibernate.Transaction;
import org.junit.Test;
import domain.Customer;
import domain.Linkman;
import utils.HibernateUtils;
/**
* hibernate HQL演示，HQL是面向对象的，里面的参数都是对象名和对象的属性名不要填写标的列名
* @author Administrator
*
*/
public class Demo1 {
/*
* 聚合函数查询,count为例 count和sql一样可以count * 或者 count 某个列
*/
@Test
public void testRun8() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
//1.直接转为需要的类型
// List<Long> list = session.createQuery("select count(lmk_id) from Linkman l").list();
List<Long> list = session.createQuery("select count(l) from Linkman l").list();
long longValue = list.get(0).longValue();
System.out.println(longValue);
//2List泛型写为数字类的父类Number抽象类
List<Number> list1 = session.createQuery("select count(l) from Linkman l").list();
long longValue1 = list1.get(0).longValue();
System.out.println(longValue);
tr.commit();
}
/*
* 投影查询，只查询表中的某个字段或者几个字段
* 封装到对象中，需要在Bean中提供相应字段的构造函数
* HQL语句稍微变化，把需要查找的字段加入到构造方法中new Linkman(l.lkm_id,l.lkm_name)
*/
@Test
public void testRun7() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
List<Linkman> list = session.createQuery("select new Linkman(l.lkm_id,l.lkm_name) from Linkman l").list();
//遍历集合
for (Linkman linkman : list) {
System.out.println(linkman);
}
tr.commit();
}
/*
* 投影查询，只查询表中的某个字段或者几个字段
* 默认返回Object[]数组
*/
@Test
public void testRun6() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
//获得query对象
List<Object[]> list = session.createQuery("select l.lkm_name,l.lkm_id from Linkman l").list();
//遍历数组
for (Object[] objects : list) {
System.out.println(Arrays.toString(objects));
}
tr.commit();
}
/*
* 带条件的分页查询
*/
@Test
public void testRun5() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
//获得query对象
Query query = session.createQuery("from Linkman where lkm_name like ? order by lkm_id");
//设置分页的参数
query.setFirstResult(0);
query.setMaxResults(2);
//设置条件
//使用setParameter("?号的位置，默认从0开始","参数的值"); 不用考虑参数的具体类型
query.setParameter(0, "%人%");
//获得数据
List<Linkman> list = query.list();
System.out.println(list.size());
tr.commit();
}
/*
* 分页查询
*/
@Test
public void testRun4() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
List<Linkman> list = session.createQuery("from Linkman order by lkm_id").setFirstResult(0).setMaxResults(3).list();//降序
System.out.println(list.size());
// for (Linkman lkm : list) {
// System.out.println(lkm);
// }
tr.commit();
}
/*
* 排序查询
*/
@Test
public void testRun3() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
// List<Customer> list = session.createQuery("from Customer order by cust_id asc").list();//升序，不谢asc也可以
List<Customer> list = session.createQuery("from Customer order by cust_id desc").list();//降序
for (Customer customer : list) {
System.out.println(customer);
}
tr.commit();
}
/*
* 使用别名的方式
*/
@Test
public void testRun2() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
//以下两种方法都可以，写不写select 都可以 写的话需要别名
// List<Customer> list = session.createQuery("from Customer c").list();
List<Customer> list = session.createQuery("select c from Customer c").list();
System.out.println(list.size());
tr.commit();
}
/*
* HQL基本的查询格式,支持方法链.
*/
@Test
public void testRun1() {
Session session = HibernateUtils.getCurrentSession();
Transaction tr = session.beginTransaction();
List<Customer> list = session.createQuery("from Customer").list();//Customer是对象名称
System.out.println(list.size());
tr.commit();
}
}