2019独角兽企业重金招聘Python工程师标准>>>

  1 package com.yl.hibernate.entities;
  2
  3 import static org.junit.Assert.*;
  4
  5 import java.util.Date;
  6
  7 import org.hibernate.Session;
  8 import org.hibernate.SessionFactory;
  9 import org.hibernate.Transaction;
 10 import org.hibernate.cfg.Configuration;
 11 import org.hibernate.service.ServiceRegistry;
 12 import org.hibernate.service.ServiceRegistryBuilder;
 13 import org.junit.After;
 14 import org.junit.Before;
 15 import org.junit.Test;
 16
 17 public class HibernateTest {
 18
 19     private SessionFactory sessionFactory;
 20     private Session session;
 21     private Transaction transaction;
 22
 23     @Before
 24     public void init() {
 25         Configuration configuration = new Configuration().configure();
 26         ServiceRegistry serviceRegistry =
 27                 new ServiceRegistryBuilder().applySettings(configuration.getProperties())
 28                                             .buildServiceRegistry();
 29
 30         sessionFactory = configuration.buildSessionFactory(serviceRegistry);
 31
 32         session = sessionFactory.openSession();
 33
 34         transaction = session.beginTransaction();
 35     }
 36     @After
 37     public void destory() {
 38         transaction.commit();
 39
 40         session.close();
 41
 42         sessionFactory.close();
 43     }
 44
 45     @Test
 46     public void testSessionCache() {
 47         News news = (News)session.get(News.class, 21);
 48         System.out.println(news);
 49         session.flush();
 50         News news2 = (News)session.get(News.class, 21);
 51         System.out.println(news2);
 52
 53         System.out.println(news == news2);//true
 54     }
 55
 56     /**
 57      * flush：使数据库表中的记录和Session缓存中的对象的状态保持一致。为了保持一致，则可能会发送对应的SQL语句。
 58      *     1.在Transaction的commit()方法中：先调用session的flush方法，再提交事务
 59      *  2.flush()方法可能会发送SQL语句，但不会提交事务
 60      *  3.注意：在为提交事务或显示调用session.flush()方法 之前，也有可能会flush()操作。
 61      *      1).执行HQL或QBC查询，会先进行flush操作，以得到数据表的最新纪录
 62      *      2).若记录的ID是由底层数据库使用自增的方式生成的，则在调用save方法时，就会立即发送INSERT语句
 63      *  因为save方法后，必须保证对象的ID是存在的！
 64      */
 65     @Test
 66     public void testFlush2() {
 67         News news = new News("Hibernate", "oracle", new Date());
 68         session.save(news);
 69     }
 70
 71     @Test
 72     public void testFlush() {
 73         News news = (News)session.get(News.class, 21);
 74         news.setAuthor("Bruce Eckel");
 75
 76         News news2 = (News)session.createCriteria(News.class).uniqueResult();
 77         System.out.println(news2);
 78     }
 79
 80     /**
 81      * refresh():会强制发送SELECT 语句，以使Session缓存中对象的状态和数据表中对应的记录保持一致！
 82      */
 83     @Test
 84     public void testRefresh() {
 85         News news = (News) session.get(News.class, 21);
 86         System.out.println(news);
 87         session.refresh(news);
 88         System.out.println(news);
 89     }
 90
 91     /**
 92      * clear():清理缓存
 93      */
 94     @Test
 95     public void testClear() {
 96         News news1 = (News) session.get(News.class, 21);
 97         session.clear();
 98         News news2 = (News) session.get(News.class, 21);
 99     }
100 }