Hibernate乐观锁兑现之Timestamp

通过在表中及POJO中增加一个Timestamp字段来表示记录的最后更新时间，来达到多用户同时更改一条数据的冲突，这个timestamp由数据库自动添加，无需人工干预

数据库结构：

create table studentTimestamp(id varchar(32),name varchar(32),lastUpdateDateTime timestamp not null default current_timestamp on update current_timestamp);

pojos:

package Timestamp;

import java.util.Date;

public class Student {
  private String id;
  private String name;
  private Date lastUpdateDateTime;
public String getId() {
    return id;
}
public Date getLastUpdateDateTime() {
    return lastUpdateDateTime;
}
public void setLastUpdateDateTime(Date lastUpdateDateTime) {
    this.lastUpdateDateTime = lastUpdateDateTime;
}
public void setId(String id) {
    this.id = id;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}



}

 Student.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<!-- 
    Mapping file autogenerated by MyEclipse - Hibernate Tools
-->
<hibernate-mapping>
<class name="Timestamp.Student" table="studentTimestamp" >
    <id name="id" unsaved-value="null">
      <generator class="uuid.hex"></generator>
    </id>
    <!-- timestamp标签必须跟在id标签后面 -->
    <timestamp name="lastUpdateDateTime" column="lastUpdateDateTime"></timestamp>
    <property name="name" type="string" column="name"></property>  
</class>

</hibernate-mapping>

Hibernate.cfg.xml

<?xml version='1.0' encoding='UTF-8'?>
<!DOCTYPE hibernate-configuration PUBLIC
          "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
          "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<!-- Generated by MyEclipse Hibernate Tools.                   -->
<hibernate-configuration>

<session-factory>
    <property name="connection.username">root</property>
    <property name="connection.url">
        jdbc:mysql://localhost:3306/schoolproject?characterEncoding=gb2312&amp;useUnicode=true
    </property>
    <property name="dialect">
        org.hibernate.dialect.MySQLDialect
    </property>
    <property name="myeclipse.connection.profile">mysql</property>
    <property name="connection.password">1234</property>
    <property name="connection.driver_class">
        com.mysql.jdbc.Driver
    </property>
    <property name="hibernate.dialect">
        org.hibernate.dialect.MySQLDialect
    </property>
    <property name="hibernate.show_sql">true</property>
    <property name="current_session_context_class">thread</property>
    <property name="jdbc.batch_size">15</property>
    <mapping resource="Timestamp/Student.hbm.xml" />




</session-factory>

</hibernate-configuration>

测试代码：

package Timestamp;


import java.io.File;
import java.util.Iterator;
import java.util.Set;

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

public class Test {


    public static void main(String[] args) {

        String filePath=System.getProperty("user.dir")+File.separator+"src/Timestamp"+File.separator+"hibernate.cfg.xml";
        File file=new File(filePath);
        System.out.println(filePath);
        SessionFactory sessionFactory=new Configuration().configure(file).buildSessionFactory();
        Session session=sessionFactory.openSession();
        Transaction t=session.beginTransaction();
        
        Student stu=new Student();
        stu.setName("tom11");
        session.save(stu);
        t.commit();
      
        
        /*
         * 模拟多个session操作student数据表
         */
        
        Session session1=sessionFactory.openSession();
        Session session2=sessionFactory.openSession();
        Student stu1=(Student)session1.createQuery("from Student s where s.name='tom11'").uniqueResult();
        Student stu2=(Student)session2.createQuery("from Student s where s.name='tom11'").uniqueResult();
        
        //这时候，两个版本号是相同的
        System.out.println("v1="+stu1.getLastUpdateDateTime()+"--v2="+stu2.getLastUpdateDateTime());
        
        Transaction tx1=session1.beginTransaction();
        stu1.setName("session1");
        tx1.commit();
        //这时候，两个版本号是不同的，其中一个的版本号递增了
        System.out.println("v1="+stu1.getLastUpdateDateTime()+"--v2="+stu2.getLastUpdateDateTime());
        
        Transaction tx2=session2.beginTransaction();
        stu2.setName("session2");
        tx2.commit();
        
        
        
    }

}

测试结果：

Hibernate: insert into studentTimestamp (lastUpdateDateTime, name, id) values (?, ?, ?)
Hibernate: select student0_.id as id0_, student0_.lastUpdateDateTime as lastUpda2_0_, student0_.name as name0_ from studentTimestamp student0_ where student0_.name='tom11'

Hibernate: select student0_.id as id0_, student0_.lastUpdateDateTime as lastUpda2_0_, student0_.name as name0_ from studentTimestamp student0_ where student0_.name='tom11'
v1=2007-12-12 16:30:53.0--v2=2007-12-12 16:30:53.0

Hibernate: update studentTimestamp set lastUpdateDateTime=?, name=? where id=? and lastUpdateDateTime=?

Exception in thread "main" org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): 

v1=2007-12-12 16:30:54.844--v2=2007-12-12 16:30:53.0

Hibernate: update studentTimestamp set lastUpdateDateTime=?, name=? where id=? and lastUpdateDateTime=?