一、安装

我是在window下安装的memcached，选择的是1.4.4版本，安装起来简单点，安装教程链接。

二、MemcachedClient客户端API使用

使用MemcachedClient连接memcached，默认端口为11211.

2.1 Java连接memcached

import java.io.IOException;
import java.net.InetSocketAddress;

/**
 * Created by wzj on 2018/6/5.
 */
public class MemcachedTest
{
    public static void main(String[] args) throws IOException
    {
        // 本地连接 Memcached 服务
        MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));
        System.out.println("Connection to server sucessful.");

        // 关闭连接
        mcc.shutdown();
    }
}

2.2 set插入数据

set的方法签名为，第二个参数是过期时间，单位是秒

public Future<Boolean> set(String key, int exp, Object o)

重复的set操作，会覆盖之前的值。

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

/**
 * Created by wzj on 2018/6/5.
 */
public class MemcachedTest
{
    public static void main(String[] args) throws IOException, ExecutionException, InterruptedException
    {
        MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));

        Future<Boolean> set = mcc.set("key1", 10, "hello");

        //查看存储状态
        System.out.println(set.get());
        
        mcc.set("key2",2,4);

        System.out.println(mcc.get("key1"));

        int value = (int) mcc.get("key2");
        System.out.println(value);

        mcc.set("key1", 10, "welcome");
        System.out.println(mcc.get("key1"));

        mcc.shutdown();
    }
}

输出结果为：

true
hello
4
welcome

2.3 add添加数据

当内存中已经有key存在，则会添加失败。如果内存中key不存在，则可以添加成功。

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

/**
 * Created by wzj on 2018/6/5.
 */
public class MemcachedTest
{
    public static void main(String[] args) throws IOException, ExecutionException, InterruptedException
    {
        // 连接本地的 Memcached 服务
        MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));

        // 添加数据
        Future fo = mcc.set("key", 900, "hello");

        // 打印状态
        System.out.println(fo.get());

        // 输出
        System.out.println(mcc.get("key"));

        // 添加
        fo = mcc.add("key", 900, "memcached");

        // 打印状态
        System.out.println("add status:" + fo.get());

        // 添加新key
        fo = mcc.add("key3", 900, "key3");

        // 打印状态
        System.out.println("add status:" + fo.get());

        // 输出
        System.out.println(mcc.get("key3"));

        // 关闭连接
        mcc.shutdown();
    }
}

输出结果为：

true
hello
add status:false
add status:true

key3

2.4 replace替换原有的key值

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

/**
 * Created by wzj on 2018/6/5.
 */
public class MemcachedTest
{
    public static void main(String[] args) throws IOException, ExecutionException, InterruptedException
    {
        //连接本地的 Memcached 服务
        MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));
        System.out.println("Connection to server sucessful.");

        // 添加第一个 key=》value 对
        Future fo = mcc.set("key", 900, "1111");

        // 输出执行 add 方法后的状态
        System.out.println(fo.get());

        // 获取键对应的值
        System.out.println(mcc.get("key"));

        // 添加新的 key
        fo = mcc.replace("key", 900, "2222");

        // 输出执行 set 方法后的状态
        System.out.println(fo.get());

        // 获取键对应的值
        System.out.println(mcc.get("key"));

        // 关闭连接
        mcc.shutdown();
    }
}

输出结果为：

true
1111
true
2222

2.5 append 和prepend

append在原有的key的value的末尾追加值。

prepend在原有的value的头位置添加值。

如果key不存在，则追加失败

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.ExecutionException;

/**
 * Created by wzj on 2018/6/5.
 */
public class MemcachedTest
{
    public static void main(String[] args) throws IOException, ExecutionException, InterruptedException
    {
        //连接本地的 Memcached 服务
        MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));
        System.out.println("Connection to server sucessful.");

        // 添加第一个 key=》value 对
        mcc.set("key", 900, "1111");

        mcc.append(1, "key", "append");

        System.out.println(mcc.get("key"));


        mcc.prepend(1, "key", "prepend");

        System.out.println(mcc.get("key"));
        // 关闭连接
        mcc.shutdown();
    }
}

2.6 CAS操作（重要）

import net.spy.memcached.CASResponse;
import net.spy.memcached.CASValue;
import net.spy.memcached.MemcachedClient;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

/**
 * Created by wzj on 2018/6/5.
 */
public class MemcachedTest
{
    public static void main(String[] args) throws IOException, ExecutionException, InterruptedException
    {
        // 连接本地的 Memcached 服务
        MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));

        // 添加数据
        Future fo = mcc.set("runoob", 900, "Free Education");

        // 输出执行 set 方法后的状态
        System.out.println("set status:" + fo.get());

        // 使用 get 方法获取数据
        System.out.println("runoob value in cache - " + mcc.get("runoob"));

        // 通过 gets 方法获取 CAS token（令牌）
        CASValue casValue = mcc.gets("runoob");

        // 输出 CAS token（令牌） 值
        System.out.println("CAS token - " + casValue);

        // 尝试使用cas方法来更新数据
        CASResponse casresp = mcc.cas("runoob", casValue.getCas(),  "11111");

        // 输出 CAS 响应信息
        System.out.println("CAS Response - " + casresp);

        // 输出值
        System.out.println("runoob value in cache - " + mcc.get("runoob"));

        //这样更新会失败的,因为期望的casid为 mcc.gets("runoob").getCas() + 1，但实际上id为mcc.gets("runoob").getCas()
        casresp = mcc.cas("runoob", mcc.gets("runoob").getCas() + 1,  "2222");

        // 输出 CAS 响应信息
        System.out.println("CAS Response - " + casresp);

        // 输出值
        System.out.println("runoob value in cache - " + mcc.get("runoob"));

        // 关闭连接
        mcc.shutdown();
    }
}

输出为：

set status:true
runoob value in cache - Free Education
CAS token - {CasValue 51/Free Education}
CAS Response - OK
runoob value in cache - 11111
CAS Response - EXISTS
runoob value in cache - 11111

memcached的每次操作，cas的id都为递增,并且cas的key一定要存在，要不然会执行失败。

import java.io.IOException;
import java.net.InetSocketAddress;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;

/**
 * Created by wzj on 2018/6/5.
 */
public class MemcachedTest
{
    public static void main(String[] args) throws IOException, ExecutionException, InterruptedException
    {
        // 连接本地的 Memcached 服务
        MemcachedClient mcc = new MemcachedClient(new InetSocketAddress("127.0.0.1", 11211));


        Future<Boolean> future = mcc.set("china", 100, "111");

        System.out.println("value = " + mcc.get("china") + "  cas id = " + mcc.gets("china").getCas());

        mcc.cas("china", mcc.gets("china").getCas(), "222");

        System.out.println("value = " + mcc.get("china") + "  cas id = " + mcc.gets("china").getCas());

        mcc.cas("china", mcc.gets("china").getCas(), "333");

        System.out.println("value = " + mcc.get("china") + "  cas id = " + mcc.gets("china").getCas());

        // 关闭连接
        mcc.shutdown();
    }
}

输出结果：

value = 111  cas id = 57
value = 222  cas id = 58
value = 333  cas id = 59