Hibernate逍遥游记-第15章处理并发问题-003乐观锁

1.

2.

drop database if exists SAMPLEDB;
create database SAMPLEDB;
use SAMPLEDB;

drop table if exists  MONKEYS ;
create table MONKEYS(
   ID bigint not null,
   NAME varchar(15),
   COUNT int,
   VERSION integer,
   primary key (ID) 
)  type=INNODB;

insert into MONKEYS(ID,NAME,COUNT,VERSION) values(1,'智多星',1000,0);

3.

package mypack;


public class Monkey{

    private Long id;

    private String name;

    private int count;
    
    private int version;
    
    public Monkey(String name, int count) {
        this.name = name;
        this.count = count;
    }

    public Monkey() {
    }


    public Long getId() {
        return this.id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return this.name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getCount() {
        return this.count;
    }

    public void setCount(int count) {
        this.count = count;
    }

    public int getVersion() {
        return this.version;
    }

    public void setVersion(int version) {
        this.version = version;
    }
}

4.

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping
PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping >

  <class name="mypack.Monkey" table="MONKEYS" >
    <id name="id" type="long" column="ID">
      <generator class="increment"/>
    </id>

    <version name="version" column="VERSION" />

    <property name="name" type="string" >
        <column name="NAME" length="15" />
    </property>

    <property name="count" type="int" column="COUNT" />
     
  </class>
</hibernate-mapping>

5.

package mypack;

import org.hibernate.*;
import org.hibernate.cfg.Configuration;
import java.util.*;

public class BusinessService extends Thread{
  public static SessionFactory sessionFactory;
  static{
     try{
       Configuration config = new Configuration();
       config.addClass(Monkey.class);
          
       sessionFactory = config.buildSessionFactory();
    }catch(RuntimeException e){e.printStackTrace();throw e;}
  }

  private Log log;

  public BusinessService(String name,Log log){
    super(name);
    this.log=log;
  }   

  public void run(){
   try{ 
    vote(); 
   }catch(Exception e){
     e.printStackTrace();
   }
  }  
  
  public void vote()throws Exception{
    Session session = sessionFactory.openSession();
    Transaction tx = null;
    try {
      
      tx = session.beginTransaction();
      log.write(getName()+":开始事务");
      Thread.sleep(500);
 
      Monkey monkey=(Monkey)session.get(Monkey.class,new Long(1));
      log.write(getName()+":查询到智多星的票数为"+monkey.getCount());
      Thread.sleep(500);

      monkey.setCount(monkey.getCount()+1);
      log.write(getName()+":把智多星的票数改为"+monkey.getCount());
      Thread.sleep(500);
       
      tx.commit();
      log.write(getName()+":提交事务");
      Thread.sleep(500);
 
    }catch(StaleObjectStateException e){
       if (tx != null) {
        tx.rollback();
       }
       e.printStackTrace();
       System.out.println(getName()+":智多星票数已被其他事务修改,本事务被撤销，请重新开始投票事务");
       log.write(getName()+":智多星票数已被其他事务修改,本事务被撤销");
    }catch (RuntimeException e) {
      if (tx != null) {
        tx.rollback();
      }
      throw e;
    }finally {
      session.close();
    }
  }

  public static void main(String args[]) throws Exception {
    Log log=new Log();
    Thread thread1=new BusinessService("猴子甲投票事务",log);
    Thread thread2=new BusinessService("猴子乙投票事务",log);
 
    thread1.start();
    thread2.start();

    while(thread1.isAlive() ||thread2.isAlive()){
     Thread.sleep(100);
    } 
    log.print();
    sessionFactory.close();
  }
}

class Log{
  private ArrayList logs=new ArrayList();
  
  synchronized void write(String text){
    logs.add(text);
  }
  public void print(){
     for (Iterator it = logs.iterator(); it.hasNext();) {
         System.out.println(it.next());
      }
  } 
} 

6.

hibernate.dialect=org.hibernate.dialect.MySQLDialect
hibernate.connection.driver_class=com.mysql.jdbc.Driver
hibernate.connection.url=jdbc:mysql://localhost:3306/sampledb
hibernate.connection.username=root
hibernate.connection.password=1234
hibernate.show_sql=true
hibernate.connection.isolation=2

7.使用timestamp

8.实现乐观锁的其他方法

9.