hibernate_HQL.md

hibernate_HQL

• 1、HQL是Hibernate Query Language即Hibernate查询语言

• 2、HQL语法举例：

  • 1>from Dept

  • 2>from Dept where deptName = 'SALES'

  • 3>from Dept dept where dept.location is not null

  • 4>from Emp order by hireDate，salary desc

• 3、执行HQL语句的步骤：

  //加载总配置文件
  Configuration configure = new Configuration().configure();
  //获得SessionFactory对象
  SessionFactory sessionFactory = configure.buildSessionFactory();
  //获取Session对象
  Session session = sessionFactory.openSession();
  String hql = "from Emp";
  Query query = session.createQuery(hql);
  List<Emp> empList = query.list();

• 4、实例

  package com.edu.test;
  
  import java.util.List;
  
  import org.hibernate.Query;
  import org.hibernate.SessionFactory;
  import org.hibernate.Transaction;
  import org.hibernate.cfg.Configuration;
  import org.hibernate.classic.Session;
  import org.junit.Test;
  
  import com.edu.bean.User;
  
  public class UserTest {
    //加载总配置文件
    Configuration configure = new Configuration().configure();
    //获得SessionFactory对象
    SessionFactory sessionFactory = configure.buildSessionFactory();
    //获取Session对象
    Session session = sessionFactory.openSession();
  
    @Test
    public void testHQLSelectAll() {
      Query query = session.createQuery("from User");
      List<?> list = query.list();
      System.out.println(list);
    }
  
    @Test
    public void testHQLSelectSome() {
      Query query = session.createQuery("from User where id > 50");
      List<?> list = query.list();
      System.out.println(list);
    }
  
    @Test
    public void testHQLSelectById() {
      Query query = session.createQuery("from User where id = 1");
      User user = (User)query.uniqueResult();
      System.out.println(user);
    }
  }