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=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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