Redis客戶端開發包：Jedis學習-高級應用

時間 2019-11-15

原文原文鏈接

事務

Jedis中事務的寫法是將redis操做寫在事物代碼塊中，以下所示，multi與exec之間爲具體的事務。html

jedis.watch (key1, key2, ...);
Transaction t = jedis.multi();
t.set("foo", "bar");
t.exec();

另外，在事務內部，是不能經過Jedis對象去獲取值的，不過能夠經過Transaction對象去獲取，以下寫法：java

package cn.edu.hdu.jedisdemo;

import java.util.Set;

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

public class App {
    public static void main(String[] args) {
        JedisPool pool = new JedisPool(new JedisPoolConfig(), "localhost");
        // / Jedis implements Closable. Hence, the jedis instance will be
        // auto-closed after the last statement.
        try (Jedis jedis = pool.getResource()) {
            // / ... do stuff here ... for example

            Transaction t = jedis.multi();
            t.set("fool", "bar");
            //jedis.get("fool");//報錯，Cannot use Jedis when in Multi. Please use Transation or reset jedis state.
            Response<String> result1 = t.get("fool");

            t.zadd("foo", 1, "barowitch");
            t.zadd("foo", 0, "barinsky");
            t.zadd("foo", 0, "barikoviev");
            Response<Set<String>> sose = t.zrange("foo", 0, -1); 
            t.exec(); // dont forget it

            String foolbar = result1.get(); // use Response.get() to retrieve things from a Response
            int soseSize = sose.get().size(); // on sose.get() you can directly call Set methods!

            // List<Object> allResults = t.exec(); // you could still get all
            // results at once, as before

            System.out.println(foolbar);
            System.out.println(soseSize);

        }
        // / ... when closing your application:
        pool.close();
    }
}

注意：Response對象的get方法要在事務exec方法執行以後調用，在t.exec()方法執行以前，Response對象是不包含結果的git

管道

有時候，咱們須要發送多個命令，一個高效的方法是使用管道；github

經過管道能夠一次性發送多條命令並在執行完後一次性將結果返回，當一組命令中每條命令都不依賴以前命令的執行結果時就能夠將這組命令一塊兒經過管道發出；redis

管道能夠減小客戶端與redis的通訊次數，提供性能。算法

以下示例：服務器

Pipeline p = jedis.pipelined();
p.set("fool", "bar"); 
p.zadd("foo", 1, "barowitch");  p.zadd("foo", 0, "barinsky"); p.zadd("foo", 0, "barikoviev");
Response<String> pipeString = p.get("fool");
Response<Set<String>> sose = p.zrange("foo", 0, -1);
p.sync(); 

int soseSize = sose.get().size();
Set<String> setBack = sose.get();

發佈/訂閱

訂閱消息

先建立一個JedisPubSub對象，而後使用Jedis對象調用subscribe方法便可，該方法須要傳入JedisPubSub對象；app

MyListener listener = new MyListener(); //listener爲JedisPubSub對象，監聽類
jedis.subscribe(listener, "channel01");

發佈消息

發佈消息調用Jedis的publish方法便可；分佈式

jedis.publish(channel, message)

注意：subscribe方法是一個阻塞的操做，且發佈和訂閱不能使用同一個Jedis對象ide

一個完整的例子

監聽事件類：

package cn.edu.hdu.jedisdemo;

import redis.clients.jedis.JedisPubSub;

class MyListener extends JedisPubSub {
    public void onMessage(String channel, String message) {
        System.out.println("get a msg: " + "channel=" + channel + ", message=" + message);
    }

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

    public void onUnsubscribe(String channel, int subscribedChannels) {
        System.out.println("channel:" + channel + ", subscribedChannels:" + subscribedChannels);
    }

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

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

    public void onPMessage(String pattern, String channel, String message) {
        System.out.println("pattern:" + pattern + ", channel:" + channel + ", message:" + message);
    }
}

main方法：

package cn.edu.hdu.jedisdemo;

import java.util.Date;
import java.util.concurrent.TimeUnit;

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

public class App {
    public static void main(String[] args) {
        final JedisPool pool = new JedisPool(new JedisPoolConfig(), "localhost");

            //兩個訂閱者
            new Thread(new Runnable() {
                @Override
                public void run() {
                    Jedis jedis = pool.getResource();
                    MyListener listener = new MyListener();
                    jedis.subscribe(listener, "channel01");

                }
            }).start();
            
            new Thread(new Runnable() {
                @Override
                public void run() {
                    Jedis jedis = pool.getResource();
                    MyListener listener = new MyListener(); //listener爲JedisPubSub對象，監聽類
                    jedis.subscribe(listener, "channel01");

                }
            }).start();

            //一個發佈者
            new Thread(new Runnable() {
                @Override
                public void run() {
                    //注意，訂閱使用的jedis對象與發佈使用的jedis對象不能相同，否者運行時會報錯
                    Jedis jedis = pool.getResource();
                    while(true){
                        try {
                            TimeUnit.SECONDS.sleep(1);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        String msg = new Date().toLocaleString();
                        System.out.println("publish a msg:" + msg);
                        jedis.publish("channel01", msg);
                    }

                }
            }).start();
            
        //pool.close();
    }
}

執行結果：

channel:channel01, subscribedChannels:1
channel:channel01, subscribedChannels:1
publish a msg:2016-7-20 10:03:42
get a msg: channel=channel01, message=2016-7-20 10:03:42
get a msg: channel=channel01, message=2016-7-20 10:03:42
publish a msg:2016-7-20 10:03:43
get a msg: channel=channel01, message=2016-7-20 10:03:43
get a msg: channel=channel01, message=2016-7-20 10:03:43
publish a msg:2016-7-20 10:03:44
get a msg: channel=channel01, message=2016-7-20 10:03:44
get a msg: channel=channel01, message=2016-7-20 10:03:44

分佈式ShardedJedis

ShardedJedis裏面採用了一致性哈希的算法，來決定每一個key的保存位置，主要用於分攤服務器的壓力。

舉個簡單的例子：

首先，開啓三個redis服務器，分別使用不一樣的端口（拷貝三份，使用不一樣的配置文件便可）：637九、6380、6381

而後，編寫測試代碼：

package cn.edu.hdu.jedisdemo;

import java.util.Arrays;
import java.util.List;
import redis.clients.jedis.Client;
import redis.clients.jedis.JedisPoolConfig;
import redis.clients.jedis.JedisShardInfo;
import redis.clients.jedis.ShardedJedis;
import redis.clients.jedis.ShardedJedisPool;

public class App {
    public static void main(String[] args) {
        // 設置鏈接池的相關配置
        JedisPoolConfig poolConfig = new JedisPoolConfig();
        poolConfig.setMaxTotal(2);
        poolConfig.setMaxIdle(1);
        poolConfig.setMaxWaitMillis(2000);
        poolConfig.setTestOnBorrow(false);
        poolConfig.setTestOnReturn(false);

        //設置Redis信息
        String host = "127.0.0.1";
        JedisShardInfo shardInfo1 = new JedisShardInfo(host, 6379, 500);
        JedisShardInfo shardInfo2 = new JedisShardInfo(host, 6380, 500);
        JedisShardInfo shardInfo3 = new JedisShardInfo(host, 6381, 500);

        //初始化ShardedJedisPool
        List<JedisShardInfo> infoList = Arrays.asList(shardInfo1, shardInfo2, shardInfo3);
        ShardedJedisPool jedisPool = new ShardedJedisPool(poolConfig, infoList);
        
        //一些基本操做
        try(ShardedJedis jedis = jedisPool.getResource()) {
            jedis.set("test", "test");
            String test = jedis.get("test");
            System.out.println(test);
        }

        //查看
        ShardedJedis jedis = jedisPool.getResource();
        jedis.set("1111", "1111");
        jedis.set("2222", "2222");
        jedis.set("3333", "3333");
        jedis.set("4444", "4444");
        Client client1 = jedis.getShard("1111").getClient();
        Client client2 = jedis.getShard("2222").getClient();
        Client client3 = jedis.getShard("3333").getClient();
        Client client4 = jedis.getShard("4444").getClient();
        //打印key在哪一個server中
        System.out.println("1111 in server:" + client1.getHost() + " and port is:" + client1.getPort());
        System.out.println("2222 in server:" + client2.getHost() + " and port is:" + client2.getPort());
        System.out.println("3333 in server:" + client3.getHost() + " and port is:" + client3.getPort());
        System.out.println("4444 in server:" + client4.getHost() + " and port is:" + client4.getPort());

        jedis.close();
        jedisPool.close();
    }
}