Memcached 是一个高性能的分布式内存对象的key-value缓存系统，用于动态Web应用以减轻数据库负载，现在也有很多人将它作为内存式数据库在使用，memcached通过它的自定义协议与客户端交互，而XMemcached就是它的一个java客户端实现。
XMemcached使用示例（本示例基于xmemcached-1.3.8.jar），总结一个，如下：
package com.wujintao.memcached; import java.io.IOException; import java.util.concurrent.TimeoutException; import net.rubyeye.xmemcached.Counter; import net.rubyeye.xmemcached.GetsResponse; import net.rubyeye.xmemcached.MemcachedClient; import net.rubyeye.xmemcached.MemcachedClientBuilder; import net.rubyeye.xmemcached.XMemcachedClientBuilder; import net.rubyeye.xmemcached.auth.AuthInfo; import net.rubyeye.xmemcached.command.BinaryCommandFactory; import net.rubyeye.xmemcached.exception.MemcachedException; import net.rubyeye.xmemcached.transcoders.StringTranscoder; import net.rubyeye.xmemcached.utils.AddrUtil; import org.junit.Test; import com.wujintao.redis.util.MD5Util; public class TestCase { @Test public void test1() throws IOException { MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11211")); // AddrUtil.getAddresses("server1:11211 server2:11211") // 宕机报警 builder.setFailureMode(true); // 使用二进制文件 builder.setCommandFactory(new BinaryCommandFactory()); /** * 设置连接池大小，即客户端个数 * In a high concurrent enviroment,you may want to pool memcached clients. * But a xmemcached client has to start a reactor thread and some thread pools, * if you create too many clients,the cost is very large. * Xmemcached supports connection pool instreadof client pool. * you can create more connections to one or more memcached servers, * and these connections share the same reactor and thread pools, * it will reduce the cost of system. * 默认的pool size是1。设置这一数值不一定能提高性能，请依据你的项目的测试结果为准。初步的测试表明只有在大并发下才有提升。 * 设置连接池的一个不良后果就是，同一个memcached的连接之间的数据更新并非同步的 * 因此你的应用需要自己保证数据更新的原子性（采用CAS或者数据之间毫无关联）。 */ builder.setConnectionPoolSize(10); MemcachedClient client = builder.build(); try { /** * 第一个是存储的key名称， * 第二个是expire时间（单位秒），超过这个时间,memcached将这个数据替换出去，0表示永久存储（默认是一个月) * 第三个参数就是实际存储的数据 */ client.set("hello", 0, "Hello,xmemcached"); String value = client.get("hello"); System.out.println("hello=" + value); client.delete("hello"); value = client.get("hello"); System.out.println("hello=" + value); // value=client.get(“hello”,3000); /** * Memcached是通过cas协议实现原子更新，所谓原子更新就是compare and set， * 原理类似乐观锁，每次请求存储某个数据同时要附带一个cas值， memcached比对这个cas值与当前存储数据的cas值是否相等， * 如果相等就让新的数据覆盖老的数据，如果不相等就认为更新失败， 这在并发环境下特别有用 */ GetsResponse<Integer> result = client.gets("a"); long cas = result.getCas(); // 尝试将a的值更新为2 if (!client.cas("a", 0, 2, cas)) { System.err.println("cas error"); } } catch (MemcachedException e) { System.err.println("MemcachedClient operation fail"); e.printStackTrace(); } catch (TimeoutException e) { System.err.println("MemcachedClient operation timeout"); e.printStackTrace(); } catch (InterruptedException e) { // ignore } try { // close memcached client client.shutdown(); } catch (IOException e) { System.err.println("Shutdown MemcachedClient fail"); e.printStackTrace(); } } @Test public void test2() throws TimeoutException, InterruptedException, MemcachedException, IOException { MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11211")); MemcachedClient client = builder.build(); client.flushAll(); if (!client.set("hello", 0, "world")) { System.err.println("set error"); } if (client.add("hello", 0, "dennis")) { System.err.println("Add error,key is existed"); } if (!client.replace("hello", 0, "dennis")) { System.err.println("replace error"); } client.append("hello", " good"); client.prepend("hello", "hello "); String name = client.get("hello", new StringTranscoder()); System.out.println(name); /** * 而删除数据则是通过deleteWithNoReply方法，这个方法删除数据并且告诉memcached * 不用返回应答，因此这个方法不会等待应答直接返回，特别适合于批量处理 */ client.deleteWithNoReply("hello"); } @Test public void incrDecr() throws IOException, TimeoutException, InterruptedException, MemcachedException { MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11211")); MemcachedClient client = builder.build(); /** * 第一个参数指定递增的key名称， 第二个参数指定递增的幅度大小， 第三个参数指定当key不存在的情况下的初始值。 * 两个参数的重载方法省略了第三个参数，默认指定为0。 */ assert (1 == client.incr("a", 5, 1)); assert (6 == client.incr("a", 5)); assert (10 == client.incr("a", 4)); assert (9 == client.decr("a", 1)); assert (7 == client.decr("a", 2)); } @Test public void counter() throws Exception { MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11211")); MemcachedClient client = builder.build(); Counter counter = client.getCounter("counter", 0); counter.incrementAndGet(); counter.decrementAndGet(); counter.addAndGet(-10); } public void auth() throws Exception { MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11211")); builder.addAuthInfo(AddrUtil.getOneAddress("localhost:11211"), AuthInfo.typical("cacheuser", "123456")); // Must use binary protocol builder.setCommandFactory(new BinaryCommandFactory()); MemcachedClient client = builder.build(); } public void nioPool() throws Exception { MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11211")); builder.setConnectionPoolSize(5); } /** *这里应该安装kestrel消息服务器，才能使用如下API生效 * @throws IOException * @throws MemcachedException * @throws InterruptedException * @throws TimeoutException */ @Test public void testGet() throws IOException, TimeoutException, InterruptedException, MemcachedException{ MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11212")); MemcachedClient client = builder.build(); String value = client.get("1"); System.out.println("hello=" + value); } @Test public void testGet2() throws IOException, TimeoutException, InterruptedException, MemcachedException{ MemcachedClientBuilder builder = new XMemcachedClientBuilder( AddrUtil.getAddresses("localhost:11212")); MemcachedClient client = builder.build(); String value = client.get("srp_"+MD5Util.MD5("3rdsearch_周杰伦")); System.out.println(value); } }
转自：http://javacrazyer.iteye.com/blog/1840119