(转)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：
[*]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：
[*]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：
[*]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：
[*]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 queue
[*]2011-12-18 23:07:14.541 INFO net.spy.memcached.MemcachedConnection:Connection state changed for sun.nio.ch.SelectionKeyImpl@1621e42
[*]CAS 2:11
[*]Value 2: Love
[*]CAS 1:11
[*]Value 1: Love
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