Memcached客户端MemcachedClient使用

Myth丶恋晨 2022-05-23 12:35 404阅读 0赞

# 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][Link 1]。

# 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

[Link 1]: http://www.runoob.com/Memcached/window-install-memcached.html