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