修改User.hbm.xml文件如下：

  1. <?xml version="1.0" encoding="UTF-8"?>

  3. <!DOCTYPE hibernate-mapping PUBLIC
  4.     "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 
  5.     "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

  7. <hibernate-mapping>
  8.     <class name="com.hb3.pack_01.model.User" table="user" 
  9.         dynamic-insert="true" 
  10.         dynamic-update="true"   
  11.     >
  12.         <id name="id" column="id" type="java.lang.Integer" unsaved-value="null">
  13.             <generator class="native" />
  14.         </id>
  15.         
  16.         <property name="name" column="name" type="java.lang.String" />
  17.         
  18.         <property name="age" column="age" type="java.lang.Integer" />
  19.     </class>
  20. </hibernate-mapping>

测试代码：

  1. package com.hb3.pack_01;

  3. import java.util.Iterator;
  4. import java.util.List;

  6. import org.hibernate.Criteria;
  7. import org.hibernate.Query;
  8. import org.hibernate.Session;
  9. import org.hibernate.SessionFactory;
  10. import org.hibernate.Transaction;
  11. import org.hibernate.cfg.Configuration;

  13. import com.hb3.pack_01.model.User;

  15. public class BusinessService {

  17.     public static void main(String[] args) {
  18.         
  19.         Configuration config = new Configuration().configure();
  20.         SessionFactory sessionFactory = config.buildSessionFactory();      
  21.         Session session = sessionFactory.openSession();
  22.         
  23.         Criteria criteria = session.createCriteria(User.class);
  24.         List<?> users = criteria.list();
  25.         Iterator<?> iterator = users.iterator();
  26.         System.out.println("id "t name/age");

  28.         while (iterator.hasNext()) {
  29.             User user = (User) iterator.next();
  30.             System.out.println(user.getId() + " "t " + user.getName() + "/" + user.getAge());
  31.         }
  32.         session.close();
  33.         
  34.         System.out.println("========================================");
  35.         
  36.         session = sessionFactory.openSession();
  37.         User user = new User();
  38.         user.setId(2);
  39.         user.setName("chenyan");
  40.         user.setAge(new Integer(24));
  41.         Transaction tx = session.beginTransaction();
  42.         session.saveOrUpdate(user);
  43.         tx.commit();
  44.         
  45.         System.out.println("========================================");
  46.         
  47.         user = new User();
  48.         user.setName("yangye");
  49.         user.setAge(new Integer(23));
  50.         tx = session.beginTransaction();
  51.         session.saveOrUpdate(user);
  52.         tx.commit();
  53.         
  54.         System.out.println("========================================");
  55.         
  56.         Query query = session.createQuery("from User");
  57.         users = query.list();
  58.         iterator = users.iterator();
  59.         System.out.println("id "t name/age");

  61.         while (iterator.hasNext()) {
  62.             user = (User) iterator.next();
  63.             System.out.println(user.getId() + " "t " + user.getName() + "/" + user.getAge());
  64.         }
  65.         
  66.         session.close();
  67.         sessionFactory.close();
  68.     }
  69. }

运行结果：

13:45:00,140  WARN ConfigurationFactory:127 - No configuration found. Configuring ehcache from ehcache-failsafe.xml  found in the classpath: jar:file:/D:/Java/MyEclipse%206.0/workspace/hb3demo/ehcache-1.2.3.jar!/ehcache-failsafe.xml
13:45:00,703  WARN EhCacheProvider:93 - Could not find configuration [org.hibernate.cache.UpdateTimestampsCache]; using defaults.
13:45:00,734  WARN EhCacheProvider:93 - Could not find configuration [org.hibernate.cache.StandardQueryCache]; using defaults.
Hibernate: select this_.id as id0_0_, this_.name as name0_0_, this_.age as age0_0_ from user this_
id   name/age
1   shenbin/28
2   chenyan/25
========================================
Hibernate: update user set name=?, age=? where id=?
========================================
Hibernate: insert into user (name, age) values (?, ?)
========================================
Hibernate: select user0_.id as id0_, user0_.name as name0_, user0_.age as age0_ from user user0_
id   name/age
1   shenbin/28
2   chenyan/24
3   yangye/23

提示：

unsaved-value可以设定的值包括：

any：总是存储

none：总是更新

null：id为null时存储（默认）

valid：id为null或是指定值时存储

值得一提的是：

正如上面的代码所示，使用查询语句查出对象后，不能使用同一个session直接对对象进行修改操作。否则会抛出异常：

Exception in thread "main" org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.hb3.pack_01.model.User#2]

......

当然这并不是saveOrUpdate方法独有的。save和update等方法使用不当也会出现如上异常。

解决方法可新建session, 或参阅：

http://www.blogjava.net/Unmi/archive/2007/08/10/135771.html

http://blog.csdn.net/tmpfree/archive/2006/03/13/623516.aspx

http://www.javaeye.com/topic/11581



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