Hibernate 乐观锁实现之 TimeStamp

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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>

</id>

</class>

</hibernate-mapping>

注解方式：

package com.ematchina.test;

import java.sql.Timestamp;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Version;

@Entity
@Table(name = "book")
public class Book {


   private int id;
   //private Timestamp lastDate;
   private String name;
   private int price;
   private int version;

   @Id
   @GeneratedValue(strategy=GenerationType.IDENTITY)
   @Column(name = "id", length = 11)
   public int getId() {
       return id;
   }
   public void setId(int id) {
       this.id = id;
   }

   @Version
   @Column(name = "version",length = 11)
   public int getVersion() {
       return version;
   }
   public void setVersion(int version) {
       this.version = version;
   }

   @Column(name = "name",length = 10)
   public String getName() {
       return name;
   }
   public void setName(String name) {
       this.name = name;
   }

   @Column(name = "price",length = 11)
   public int getPrice() {
       return price;
   }
   public void setPrice(int price) {
       this.price = price;
   }



   /*@Version
   @Temporal(TemporalType.TIMESTAMP)
   @Column(name = "lastDate")
   public Date getLastDate() {
       return lastDate;
   }
   public void setLastDate(Timestamp lastDate) {
       this.lastDate = lastDate;
   }*/


}

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">

<hibernate-configuration>

<session-factory>

jdbc:mysql://localhost:3306/schoolproject?characterEncoding=gb2312&useUnicode=true

</property>

org.hibernate.dialect.MySQLDialect

</property>

<property name="myeclipse.connection.profile">mysql</property>

com.mysql.jdbc.Driver

</property>

org.hibernate.dialect.MySQLDialect

</property>

<property name="current_session_context_class">thread</property>

</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=?