实战Memcached缓存系统（5）Memcached的CAS程序实例

1. 非CAS
首先看一个不是CAS的Memcached程序实例。实例的问题原型，见上一篇博文。
程序实例：
[java]
package com.sinosuperman.memcached; 
 
import java.io.IOException; 
import java.net.InetSocketAddress; 
 
import net.spy.memcached.MemcachedClient; 
 
public class Test { 
    public static void main(String[] args) throws IOException { 
        MemcachedClient cache = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211)); 
         
        cache.set("x", 1800, "Love"); 
 
        String obj1 = (String) cache.get("x"); 
        String obj2 = (String) cache.get("x"); 
        obj2 = "Michael"; 
         
        cache.set("x", 1800, obj2); 
        System.out.println("Non-CAS 2:\t" + obj2); 
        System.out.println("Non-CAS 1:\t" + obj1); 
    } 
} 
 
 
 
运行结果：
[plain]
2011-12-18 23:12:39.836 INFO net.spy.memcached.MemcachedConnection:  Added {QA sa=/127.0.0.1:11211, #Rops=0, #Wops=0, #iq=0, topRop=null, topWop=null, toWrite=0, interested=0} to connect queue 
2011-12-18 23:12:39.843 INFO net.spy.memcached.MemcachedConnection:  Connection state changed for sun.nio.ch.SelectionKeyImpl@b09e89 
Non-CAS 2:  Michael 
Non-CAS 1:  Love 
 
 
可见在多个Client操作时，一定会引起写不一致性的问题。
 
2. CAS
程序实例：
[java]
package com.sinosuperman.memcached; 
 
import java.io.IOException; 
import java.net.InetSocketAddress; 
 
import net.spy.memcached.CASValue; 
import net.spy.memcached.MemcachedClient; 
 
public class Test { 
    @SuppressWarnings("unchecked") 
    public static void main(String[] args) throws IOException { 
        MemcachedClient cache = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211)); 
         
        cache.set("y", 1800, "Love"); 
 
        CASValue casValue1 = cache.gets("y"); 
        CASValue casValue2 = cache.gets("y"); 
        cache.cas("y", casValue2.getCas(), casValue2.getValue()); 
         
        System.out.println("CAS 2:\t" + casValue2.getCas()); 
        System.out.println("Value 2:\t" + casValue2.getValue()); 
         
        System.out.println("CAS 1:\t" + casValue1.getCas()); 
        System.out.println("Value 1:\t" + casValue1.getValue()); 
    } 
} 
 
运行结果：
[plain]
2011-12-18 23:07:14.528 INFO net.spy.memcached.MemcachedConnection:  Added {QA sa=/127.0.0.1:11211, #Rops=0, #Wops