實戰Memcached緩衝系統（5）Memcached的CAS程式執行個體

尊重知識，轉載請註明本文來自：編程藝術家Poechant的CSDN部落格 http://blog.csdn.net/poechant

1. 非CAS

首先看一個不是CAS的Memcached程式執行個體。執行個體的問題原型，見上一篇博文。

程式執行個體：

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);}}

運行結果：

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 queue2011-12-18 23:12:39.843 INFO net.spy.memcached.MemcachedConnection:  Connection state changed for sun.nio.ch.SelectionKeyImpl@b09e89Non-CAS 2:MichaelNon-CAS 1:Love

可見在多個Client操作時，一定會引起寫不一致性的問題。

2. CAS

程式執行個體：

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());}}

運行結果：

2011-12-18 23:07:14.528 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 queue2011-12-18 23:07:14.541 INFO net.spy.memcached.MemcachedConnection:  Connection state changed for sun.nio.ch.SelectionKeyImpl@1621e42CAS 2:11Value 2:LoveCAS 1:11Value 1:Love