XMemcached使用示例--转

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