我的redis之路

这是一条不归路.

掌握基本命令

跟着官方的web版练习Try Redis即可,我做的文件try-redis.txt

现在应该学会了以下命令和数据结构:

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set/setnx
incr
del
expire
ttl
(list) lpush/rpush/lrange/lpop/rpop/llen
(set) sadd/srem/sismember/smembers/sunion
(sorted set) zadd/zrange
(hash) hset/hgetall/hmset/hget/hincrby/hdel

熟悉基本功能

了解redis应用场景

  1. 缓存(会话缓存或FPC全页缓存)
  2. 队列
  3. 排行榜/计数榜(得益于其原子递增操作)
  4. pub/sub

写个应用

利用其发布/订阅功能写个聊天应用.

1.安装redis

按照官网https://redis.io/download做2分钟搞定.

2.来看一下demo

一个客户端发布,另一个订阅

先开订阅者:

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$ ./redis-cli 
127.0.0.1:6379> SUBSCRIBE test-channel
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "test-channel"
3) (integer) 1

发布者再发送消息:

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127.0.0.1:6379> PUBLISH test-channel hello
(integer) 1
127.0.0.1:6379> PUBLISH test-channel "how are you"
(integer) 1

这时候订阅者会收到消息:

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1) "message"
2) "test-channel"
3) "hello"
1) "message"
2) "test-channel"
3) "how are you"

更多可以参考文档https://redis.io/topics/pubsub.
其最后给出了以一个ruby写的多人聊天室,我们要用java来写.

3.java版聊天室

关于java操作redis的库有很多,我们使用Jedis.

关于Jedis获取redis实例的操作见:https://github.com/xetorthio/jedis/wiki/Getting-started
操作发布/订阅见:https://github.com/xetorthio/jedis/wiki/AdvancedUsage

现在的需求:聊天室是多人的,可以发送接受消息.
分解开来:用户A发送的消息会推送给所有用户,每当有一个用户上线就需要多一个订阅者和发送者.

服务器:

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package com.jimo;

import redis.clients.jedis.Jedis;
import redis.clients.jedis.JedisPool;
import redis.clients.jedis.JedisPoolConfig;

public class ChatServer {

    private JedisPool pool;
    private PSListener listener;

    ChatServer() {
        pool = new JedisPool(new JedisPoolConfig(), "localhost");
        listener = new PSListener();
    }

    public void stop() {
        pool.close();
    }

    /**
     * 每增加用户就开一个线程防止阻塞
     *
     * @param userName
     */
    public void addUser(String userName) {
        new Thread() {
            @Override
            public void run() {
                JedisPool pool1 = new JedisPool(new JedisPoolConfig(), "localhost");
                try (Jedis jedis = pool1.getResource()) {
                    jedis.psubscribe(listener, "chat*");
                }
            }
        }.start();
    }

    /**
     * 将消息推送给所有用户
     *
     * @param msg
     */
    public void sendMsg(String msg) {
        try (Jedis jedis = pool.getResource()) {
            jedis.publish("chat4", msg);
        }
    }
}

测试:

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package com.jimo;

public class Test {
    public static void main(String[] args) {
        ChatServer chatServer = new ChatServer();

        chatServer.addUser("chat1");
        chatServer.addUser("chat2");
        chatServer.sendMsg("hello");
        chatServer.sendMsg("xixihaha");


        chatServer.stop();
    }
}

Listener:

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package com.jimo;

import redis.clients.jedis.JedisPubSub;

public class PSListener extends JedisPubSub {

    public void onMessage(String channel, String message) {
        System.out.println("收到channel[" + channel + "]的消息:" + message);
    }

    public void onPMessage(String pattern, String channel, String message) {
        System.out.println("p收到channel[" + channel + "]的消息:" + message);
    }

    public void onSubscribe(String channel, int subscribedChannels) {
        System.out.println(channel + "被订阅");
    }

    public void onUnsubscribe(String channel, int subscribedChannels) {
    }

    public void onPUnsubscribe(String pattern, int subscribedChannels) {
    }

    public void onPSubscribe(String pattern, int subscribedChannels) {
        System.out.println(subscribedChannels + "被订阅:" + pattern);
    }
}

上面的代码是有问题的,自己发送的消息也会被推送回来.