hibernate查询某一个对象后，执行createSQLQuery查询出现的问题

标签：hibernate   private   public   create   import   

最近工作中碰到了一个奇怪问题，特别做下笔记：

user表里的数据，是1，1和2，2，分别为id和name字段。

代码如下：

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;




public class Test {
private static final SessionFactory sessionFactory;
   static {
       try {
           // Create the SessionFactory from hibernate.cfg.xml
           sessionFactory = new Configuration().configure().buildSessionFactory();
       } catch (Throwable ex) {
           // Make sure you log the exception, as it might be swallowed
           System.err.println("Initial SessionFactory creation failed." + ex);
           throw new ExceptionInInitializerError(ex);
       }
   }
   public static SessionFactory getSessionFactory() {
       return sessionFactory;
   }
   public static void main(String[] args) {
Session session = sessionFactory.openSession();
Transaction tr = session.beginTransaction();
tr.begin();
User user = (User) session.load(User.class, 1);
user.setName("2");
session.saveOrUpdate(user);
int num = (Integer) session.createSQLQuery("select count(*) num from user where name = 2 ").addScalar("num", Hibernate.INTEGER).uniqueResult();
System.out.println(num);
tr.commit();
}

打印结果：

Hibernate: select user0_.id as id0_0_, user0_.name as name0_0_ from user user0_ where user0_.id=?
Hibernate: select count(*) num from user where name = 2 
1
Hibernate: update user set name=? where id=?

也就是说通过session.createSQLQuery这个方法并没有先去更新user对象，所以结果还是1，而我想要的结果是2，所以会出现这样错误

修改代码 ：

import org.hibernate.Hibernate;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
import org.hibernate.cfg.Configuration;




public class Test {
private static final SessionFactory sessionFactory;
   static {
       try {
           // Create the SessionFactory from hibernate.cfg.xml
           sessionFactory = new Configuration().configure().buildSessionFactory();
       } catch (Throwable ex) {
           // Make sure you log the exception, as it might be swallowed
           System.err.println("Initial SessionFactory creation failed." + ex);
           throw new ExceptionInInitializerError(ex);
       }
   }
   public static SessionFactory getSessionFactory() {
       return sessionFactory;
   }
   public static void main(String[] args) {
Session session = sessionFactory.openSession();
Transaction tr = session.beginTransaction();
tr.begin();
User user = (User) session.load(User.class, 1);
user.setName("2");
session.saveOrUpdate(user);
int num = (Integer) session.createQuery("from User where name = 2 ").list().size();
System.out.println(num);
tr.commit();
}
}

执行结果：

Hibernate: select user0_.id as id0_0_, user0_.name as name0_0_ from user user0_ where user0_.id=?
Hibernate: update user set name=? where id=?
Hibernate: select user0_.id as id0_, user0_.name as name0_ from user user0_ where user0_.name=2
2

这里就是先更新了user对象后，再来查询了，所以这种情况是正确的

总结：如果跟新了查出来的对象，saveorupdate了，然后用session.createSQLQuery方法的时候，也是查询不到修改的对象的，从打印语句可以看出来：

先查询了，然后再更新了哦，所以会出现问题的

本文出自 “追随心的彼岸” 博客，谢绝转载！

hibernate查询某一个对象后，执行createSQLQuery查询出现的问题

标签：hibernate   private   public   create   import   

原文地址：http://qa962839575.blog.51cto.com/6819179/1587098