hibernate之hql查询

package Usertest;

import java.util.List;

import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.query.Query;
import org.junit.Test;

import text.User;

public class Hql {
	
		@Test  
		public void Query1(){//搜索User中的所有属性输出姓名
			// TODO Auto-generated method stub
			SessionFactory sf = null;	
			Session session = null;
			Transaction ts = null;
			try {
	  			sf = HibernateUtil.getSessionFactory();
				session = sf.getCurrentSession();
				ts = session.beginTransaction();
				User user=new User();
				Query query = session.createQuery("from User");
				List users = query.list();
				for(int i=0;i<users.size();i++)
				{
						user =(User)users.get(i);
						System.out.println(i+"--"+user.getUsername());
				}
				
				ts.commit();
			} catch (HibernateException e) {
				// TODO Auto-generated catch block
				if(ts != null)
				{
					ts.rollback();
				}
				e.printStackTrace();
			}
		}
		@Test  
		//搜索多个属性返回数组
		public void Queryattributes(){
			// TODO Auto-generated method stub
			SessionFactory sf = null;	
			Session session = null;
			Transaction ts = null;	
			try {
	  			sf = HibernateUtil.getSessionFactory();
				session = sf.getCurrentSession();
				ts = session.beginTransaction();
				User user=new User();
				Query query = session.createQuery("select u.username, u.password from User as u");
				List users = query.list();
				for(int i=0;i<users.size();i++)
				{
					Object obj[] =(Object[])users.get(i);
					System.out.println(obj[0]+"的密码为:"+obj[1]);
				}
				

				ts.commit();
			} catch (HibernateException e) {
				// TODO Auto-generated catch block
				if(ts != null)
				{
					ts.rollback();
				}
				e.printStackTrace();
			}
		}
		@Test 
		//指定新建一个对象传回，注意，此处需要在实体类中创建含参构造方法和无参构造方法，无参构造方法是为了其他语句使用，因为系统默认是调用无参的构造方法
		public void Querynewattributes(){
			// TODO Auto-generated method stub
			SessionFactory sf = null;	
			Session session = null;
			Transaction ts = null;
			try {
	  			sf = HibernateUtil.getSessionFactory();
				session = sf.getCurrentSession();
				ts = session.beginTransaction();
			  
				Query query = session.createQuery("select new User(u.username,u.password) from User as u");
			    List users = query.list();
			    for(int i=0;i<users.size();i++)
			    {
					User user =(User)users.get(i);
					System.out.println(user.getUsername()+"的密码为:"+user.getPassword());
					
			   }
				ts.commit();
			} catch (HibernateException e) {
				// TODO Auto-generated catch block
				if(ts != null)
				{
					ts.rollback();
				}
				e.printStackTrace();
			}
		}
		@Test 
		public void countattributes(){//返回共有多少条记录，平均年龄以及最大年龄
			// TODO Auto-generated method stub
			SessionFactory sf = null;	
			Session session = null;
			Transaction ts = null;
			
			try {
	  			sf = HibernateUtil.getSessionFactory();
				session = sf.getCurrentSession();
				ts = session.beginTransaction();
			
				Query query = session.createQuery("select count(*) from User");
				Object count  =  (Object)query.uniqueResult();
			    System.out.println("共有"+count+"条记录");

			    query = session.createQuery("select avg(u.age) from User u");
				Number average =(Number)query.uniqueResult();
				System.out.println("平均年龄为："+average);
				
			    query = session.createQuery("select max(u.age) from User u");
							Number max =(Number)query.uniqueResult();
							System.out.println("最大年龄为："+max);

				ts.commit();
			} catch (HibernateException e) {
				// TODO Auto-generated catch block
				if(ts != null)
				{
					ts.rollback();
				}
				e.printStackTrace();
			}
		}
		@Test 
		//提取第5-9个对象
		public void  query(){
			// TODO Auto-generated method stub
			SessionFactory sf = null;	
			Session session = null;
			Transaction ts = null;
			
			try {
	  			sf = HibernateUtil.getSessionFactory();
				session = sf.getCurrentSession();
				ts = session.beginTransaction();
				Query  query=session.createQuery("from User");
				query.setFirstResult(4);
				query.setMaxResults(5);
				List result=query.list();
				 for(int i=0;i<result.size();i++)
				    {
						User user =(User)result.get(i);
						System.out.println(  user.getId()+" "+user.getUsername()+"--"+user.getPassword());
						
				   }

				ts.commit();
			} catch (HibernateException e) {
				// TODO Auto-generated catch block
				if(ts != null)
				{
					ts.rollback();
				}
				e.printStackTrace();
			}
		}
		@Test 
		//嵌套子查询
		public void doublequery(){
			// TODO Auto-generated method stub
			SessionFactory sf = null;	
			Session session = null;
			Transaction ts = null;
			
			try {
	  			sf = HibernateUtil.getSessionFactory();
				session = sf.getCurrentSession();
				ts = session.beginTransaction();
				
			Query query = session.createQuery("from User u where u.age>(select avg(age) from User)");
		    List users = query.list();
			for(int i=0;i<users.size();i++)
			{
				User user =(User)users.get(i);
				 System.out.println(user.getId()+"--姓名："+user.getUsername()+"--年龄"+user.getAge());
							} 

				ts.commit();
			} catch (HibernateException e) {
				// TODO Auto-generated catch block
				if(ts != null)
				{
					ts.rollback();
				}
				e.printStackTrace();
			}
		}
}

注意，创建新对象需要在实体类中创建含参构造方法和无参构造方法，无参构造方法是为了其他语句使用，因为系统默认是调用无参的构造方法

public User(){}
public User(int id, String username, String password, String gender, int age) {

	this.id = id;
	this.username = username;
	this.password = password;
	this.gender = gender;
	this.age = age;
}

搜索user中的所有属性输出姓名

搜索多个属性返回数组

统计总的记录数以及年龄的最大值和平均值输出结果

嵌套子查询

提取第5-9个对象结果

就简单运行这几个啦~