二、发布/订阅模式(类似于MQ的主题模式-只能消费订阅之后发布的消息，一个消息可以被多个订阅者消费)
1.客户端发布/订阅
1.1 普通的发布/订阅
除了实现任务队列外，redis还提供了一组命令可以让开发者实现"发布/订阅"(publish/subscribe)模式。"发布/订阅"模式同样可以实现进程间的消息传递，其原理如下:
"发布/订阅"模式包含两种角色，分别是发布者和订阅者。订阅者可以订阅一个或者多个频道(channel),而发布者可以向指定的频道(channel)发送消息，所有订阅此频道的订阅者都会收到此消息。
(1)发布消息
发布者发布消息的命令是 publish,用法是 publish channel message，如向 channel1.1说一声hi
127.0.0.1:6379> publish channel:1 hi (integer) 0
这样消息就发出去了。返回值表示接收这条消息的订阅者数量。发出去的消息不会被持久化，也就是有客户端订阅channel:1后只能接收到后续发布到该频道的消息，之前的就接收不到了。
(2)订阅频道
订阅频道的命令是 subscribe，可以同时订阅多个频道，用法是 subscribe channel1 [channel2 ...],例如新开一个客户端订阅上面频道:(不会收到消息，因为不会收到订阅之前就发布到该频道的消息)
127.0.0.1:6379> subscribe channel:1 Reading messages... (press Ctrl-C to quit) 1) "subscribe" 2) "channel:1" 3) (integer) 1
执行上面命令客户端会进入订阅状态，处于此状态下客户端不能使用除subscribe、unsubscribe、psubscribe和punsubscribe这四个属于"发布/订阅"之外的命令，否则会报错。
进入订阅状态后客户端可能收到3种类型的回复。每种类型的回复都包含3个值，第一个值是消息的类型，根据消类型的不同，第二个和第三个参数的含义可能不同。
消息类型的取值可能是以下3个:
(1)subscribe。表示订阅成功的反馈信息。第二个值是订阅成功的频道名称，第三个是当前客户端订阅的频道数量。
(2)message。表示接收到的消息，第二个值表示产生消息的频道名称，第三个值是消息的内容。
(3)unsubscribe。表示成功取消订阅某个频道。第二个值是对应的频道名称，第三个值是当前客户端订阅的频道数量，当此值为0时客户端会退出订阅状态，之后就可以执行其他非"发布/订阅"模式的命令了。
(3)第一个客户端重新向channel:1发送一条消息
127.0.0.1:6379> publish channel:1 hi (integer) 1
返回值表示订阅此频道的数量
c
上面订阅的客户端:
127.0.0.1:6379> subscribe channel:1 Reading messages... (press Ctrl-C to quit) 1) "subscribe" 2) "channel:1" 3) (integer) 1 1) "message" 2) "channel:1" 3) "hi"
红字部分表示成功的收到消息(依次是消息类型，频道，消息内容)
1.2 按照规则发布/订阅
除了可以使用subscribe命令订阅指定的频道外，还可以使用psubscribe命令订阅指定的规则。规则支持通配符格式。命令格式为 psubscribe pattern [pattern ...]订阅多个模式的频道。
通配符中?表示1个占位符，*表示任意个占位符(包括0)，?*表示1个以上占位符。
例如:
(1)订阅者订阅三个通配符频道
127.0.0.1:6379> psubscribe c? b* d?* Reading messages... (press Ctrl-C to quit) 1) "psubscribe" 2) "c?" 3) (integer) 1 1) "psubscribe" 2) "b*" 3) (integer) 2 1) "psubscribe" 2) "d?*" 3) (integer) 3
(2)新开一个客户端发送到指定频道
C:\Users\liqiang>redis-cli 127.0.0.1:6379> publish c m1 (integer) 0 127.0.0.1:6379> publish c1 m1 (integer) 1 127.0.0.1:6379> publish c11 m1 (integer) 0 127.0.0.1:6379> publish b m1 (integer) 1 127.0.0.1:6379> publish b1 m1 (integer) 1 127.0.0.1:6379> publish b11 m1 (integer) 1 127.0.0.1:6379> publish d m1 (integer) 0 127.0.0.1:6379> publish d1 m1 (integer) 1 127.0.0.1:6379> publish d11 m1 (integer) 1
上面返回值为1表示被订阅者所接受，可以匹配上面的通配符。
订阅者客户端:
127.0.0.1:6379> psubscribe c? b* d?* Reading messages... (press Ctrl-C to quit) 1) "psubscribe" 2) "c?" 3) (integer) 1 1) "psubscribe" 2) "b*" 3) (integer) 2 1) "psubscribe" 2) "d?*" 3) (integer) 3 1) "pmessage" 2) "c?" 3) "c1" 4) "m1" 1) "pmessage" 2) "b*" 3) "b" 4) "m1" 1) "pmessage" 2) "b*" 3) "b1" 4) "m1" 1) "pmessage" 2) "b*" 3) "b11" 4) "m1" 1) "pmessage" 2) "d?*" 3) "d1" 4) "m1" 1) "pmessage" 2) "d?*" 3) "d11" 4) "m1"
注意:
(1)使用psubscribe命令可以重复订阅同一个频道，如客户端执行了psubscribe c? c?*。这时向c1发布消息客户端会接受到两条消息，而同时publish命令的返回值是2而不是。.同样的，如果有另一个客户端执行了subscribe c1 和psubscribe c?*的话，向c1发送一条消息该客户端也会收到两条消息(但是是两种类型:message和pmessage)，同时publish命令也返回2.
(2)punsubscribe命令可以退订指定的规则，用法是: punsubscribe [pattern [pattern ...]],如果没有参数则会退订所有规则。
(3)使用punsubscribe只能退订通过psubscribe命令订阅的规则，不会影响直接通过subscribe命令订阅的频道；同样unsubscribe命令也不会影响通过psubscribe命令订阅的规则。另外需要注意punsubscribe命令退订某个规则时不会将其中的通配符展开，而是进行严格的字符串匹配，所以punsubscribe * 无法退订c*规则，而是必须使用punsubscribe c*才可以退订。
2.Java程序实现发布者订阅者模式
1.生产者
import redis.clients.jedis.Jedis; /** * @Author: cc * @Description * @Date: 21:29 2020/10/9 */ public class MessageProducer extends Thread { public static final String CHANNEL_KEY = "channel:1"; private volatile int count; public void putMessage(String message) { Jedis jedis = JedisPoolUtils.getJedis(); Long publish = jedis.publish(CHANNEL_KEY, message);//返回订阅者数量 System.out.println(Thread.currentThread().getName() + " put message,count=" + count+",subscriberNum="+publish); count++; } @Override public synchronized void run() { for (int i = 0; i < 5; i++) { putMessage("message" + count); } } public static void main(String[] args) { MessageProducer messageProducer = new MessageProducer(); Thread t1 = new Thread(messageProducer, "thread1"); Thread t2 = new Thread(messageProducer, "thread2"); Thread t3 = new Thread(messageProducer, "thread3"); Thread t4 = new Thread(messageProducer, "thread4"); Thread t5 = new Thread(messageProducer, "thread5"); t1.start(); t2.start(); t3.start(); t4.start(); t5.start(); } }
结果:
thread1 put message,count=0,subscriberNum=0 thread1 put message,count=1,subscriberNum=0 thread1 put message,count=2,subscriberNum=0 thread1 put message,count=3,subscriberNum=0 thread1 put message,count=4,subscriberNum=0 thread4 put message,count=5,subscriberNum=0 thread4 put message,count=6,subscriberNum=0 thread4 put message,count=7,subscriberNum=0 thread4 put message,count=8,subscriberNum=0 thread4 put message,count=9,subscriberNum=0 thread5 put message,count=10,subscriberNum=0 thread5 put message,count=11,subscriberNum=0 thread5 put message,count=12,subscriberNum=0 thread5 put message,count=13,subscriberNum=0 thread5 put message,count=14,subscriberNum=0 thread2 put message,count=15,subscriberNum=0 thread2 put message,count=16,subscriberNum=0 thread2 put message,count=17,subscriberNum=0 thread2 put message,count=18,subscriberNum=0 thread2 put message,count=19,subscriberNum=0 thread3 put message,count=20,subscriberNum=0 thread3 put message,count=21,subscriberNum=0 thread3 put message,count=22,subscriberNum=0 thread3 put message,count=23,subscriberNum=0 thread3 put message,count=24,subscriberNum=0
2.消费者
(1)subscribe实现订阅消费消息(开启两个线程订阅消息)
import redis.clients.jedis.Jedis; import redis.clients.jedis.JedisPubSub; /** * @Author: cc * @Description * @Date: 22:34 2020/10/9 */ public class MessageConsumer implements Runnable { public static final String CHANNEL_KEY = "channel:1";//频道 public static final String EXIT_COMMAND = "exit";//结束程序的消息 private MyJedisPubSub myJedisPubSub = new MyJedisPubSub();//处理接收消息 public void consumerMessage() { Jedis jedis = JedisPoolUtils.getJedis(); jedis.subscribe(myJedisPubSub, CHANNEL_KEY);//第一个参数是处理接收消息，第二个参数是订阅的消息频道 } @Override public void run() { while (true) { consumerMessage(); } } public static void main(String[] args) { MessageConsumer messageConsumer = new MessageConsumer(); Thread t1 = new Thread(messageConsumer, "thread5"); Thread t2 = new Thread(messageConsumer, "thread6"); t1.start(); t2.start(); } } /** * 继承JedisPubSub，重写接收消息的方法 */ class MyJedisPubSub extends JedisPubSub { @Override /** JedisPubSub类是一个没有抽象方法的抽象类,里面方法都是一些空实现 * 所以可以选择需要的方法覆盖,这儿使用的是SUBSCRIBE指令，所以覆盖了onMessage * 如果使用PSUBSCRIBE指令，则覆盖onPMessage方法 * 当然也可以选择BinaryJedisPubSub,同样是抽象类，但方法参数为byte[] **/ public void onMessage(String channel, String message) { System.out.println(Thread.currentThread().getName()+"-接收到消息:channel=" + channel + ",message=" + message); //接收到exit消息后退出 if (MessageConsumer.EXIT_COMMAND.equals(message)) { System.exit(0); } } }
我们再次启动生产者生产消息,生产者控制台:
thread5 put message,count=0,subscriberNum=2 thread5 put message,count=1,subscriberNum=2 thread5 put message,count=2,subscriberNum=2 thread5 put message,count=3,subscriberNum=2 thread5 put message,count=4,subscriberNum=2 thread3 put message,count=5,subscriberNum=2 thread3 put message,count=6,subscriberNum=2 thread3 put message,count=7,subscriberNum=2 thread3 put message,count=8,subscriberNum=2 thread3 put message,count=9,subscriberNum=2 thread2 put message,count=10,subscriberNum=2 thread2 put message,count=11,subscriberNum=2 thread2 put message,count=12,subscriberNum=2 thread2 put message,count=13,subscriberNum=2 thread2 put message,count=14,subscriberNum=2 thread4 put message,count=15,subscriberNum=2 thread4 put message,count=16,subscriberNum=2 thread4 put message,count=17,subscriberNum=2 thread4 put message,count=18,subscriberNum=2 thread4 put message,count=19,subscriberNum=2 thread1 put message,count=20,subscriberNum=2 thread1 put message,count=21,subscriberNum=2 thread1 put message,count=22,subscriberNum=2 thread1 put message,count=23,subscriberNum=2 thread1 put message,count=24,subscriberNum=2 Process finished with exit code 0
消费者控制台:
thread6-接收到消息:channel=channel:1,message=message0 thread5-接收到消息:channel=channel:1,message=message0 thread5-接收到消息:channel=channel:1,message=message1 thread6-接收到消息:channel=channel:1,message=message1 thread5-接收到消息:channel=channel:1,message=message2 thread6-接收到消息:channel=channel:1,message=message2 thread5-接收到消息:channel=channel:1,message=message3 thread6-接收到消息:channel=channel:1,message=message3 thread5-接收到消息:channel=channel:1,message=message4 thread6-接收到消息:channel=channel:1,message=message4 thread5-接收到消息:channel=channel:1,message=message5 thread6-接收到消息:channel=channel:1,message=message5 thread5-接收到消息:channel=channel:1,message=message6 thread6-接收到消息:channel=channel:1,message=message6 thread5-接收到消息:channel=channel:1,message=message7 thread6-接收到消息:channel=channel:1,message=message7 thread5-接收到消息:channel=channel:1,message=message8 thread6-接收到消息:channel=channel:1,message=message8 thread5-接收到消息:channel=channel:1,message=message9 thread6-接收到消息:channel=channel:1,message=message9 thread5-接收到消息:channel=channel:1,message=message10 thread6-接收到消息:channel=channel:1,message=message10 thread5-接收到消息:channel=channel:1,message=message11 thread6-接收到消息:channel=channel:1,message=message11 thread5-接收到消息:channel=channel:1,message=message12 thread6-接收到消息:channel=channel:1,message=message12 thread5-接收到消息:channel=channel:1,message=message13 thread6-接收到消息:channel=channel:1,message=message13 thread5-接收到消息:channel=channel:1,message=message14 thread6-接收到消息:channel=channel:1,message=message14 thread5-接收到消息:channel=channel:1,message=message15 thread6-接收到消息:channel=channel:1,message=message15 thread5-接收到消息:channel=channel:1,message=message16 thread6-接收到消息:channel=channel:1,message=message16 thread5-接收到消息:channel=channel:1,message=message17 thread6-接收到消息:channel=channel:1,message=message17 thread5-接收到消息:channel=channel:1,message=message18 thread6-接收到消息:channel=channel:1,message=message18 thread5-接收到消息:channel=channel:1,message=message19 thread6-接收到消息:channel=channel:1,message=message19 thread5-接收到消息:channel=channel:1,message=message20 thread6-接收到消息:channel=channel:1,message=message20 thread5-接收到消息:channel=channel:1,message=message21 thread6-接收到消息:channel=channel:1,message=message21 thread5-接收到消息:channel=channel:1,message=message22 thread6-接收到消息:channel=channel:1,message=message22 thread5-接收到消息:channel=channel:1,message=message23 thread6-接收到消息:channel=channel:1,message=message23 thread5-接收到消息:channel=channel:1,message=message24 thread6-接收到消息:channel=channel:1,message=message24
(2)psubscribe实现订阅消费消息(开启两个线程订阅消息)
import redis.clients.jedis.Jedis; import redis.clients.jedis.JedisPubSub; /** * @Author: cc * @Description * @Date: 22:34 2020/10/9 */ public class MessageConsumer implements Runnable { public static final String CHANNEL_KEY = "channel*";//频道 public static final String EXIT_COMMAND = "exit";//结束程序的消息 private MyJedisPubSub myJedisPubSub = new MyJedisPubSub();//处理接收消息 public void consumerMessage() { Jedis jedis = JedisPoolUtils.getJedis(); jedis.psubscribe(myJedisPubSub, CHANNEL_KEY);//第一个参数是处理接收消息，第二个参数是订阅的消息频道 } @Override public void run() { while (true) { consumerMessage(); } } public static void main(String[] args) { MessageConsumer messageConsumer = new MessageConsumer(); Thread t1 = new Thread(messageConsumer, "thread5"); Thread t2 = new Thread(messageConsumer, "thread6"); t1.start(); t2.start(); } } /** * 继承JedisPubSub，重写接收消息的方法 */ class MyJedisPubSub extends JedisPubSub { @Override public void onPMessage(String pattern, String channel, String message) { System.out.println(Thread.currentThread().getName()+"-接收到消息:pattern="+pattern+",channel=" + channel + ",message=" + message); //接收到exit消息后退出 if (MessageConsumer.EXIT_COMMAND.equals(message)) { System.exit(0); } } }
重写JedisPubSub 的onPMessage方法即可
启动生产者生产消息之后查看消费者控制台:
thread6-接收到消息:pattern=channel*,channel=channel:1,message=message0 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message0 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message1 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message1 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message2 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message2 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message3 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message3 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message4 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message4 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message5 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message5 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message6 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message6 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message7 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message7 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message8 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message8 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message9 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message9 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message10 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message10 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message11 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message11 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message12 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message12 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message13 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message13 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message14 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message14 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message15 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message15 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message16 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message16 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message17 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message17 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message18 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message18 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message19 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message19 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message20 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message20 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message21 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message21 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message22 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message22 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message23 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message23 thread5-接收到消息:pattern=channel*,channel=channel:1,message=message24 thread6-接收到消息:pattern=channel*,channel=channel:1,message=message24
补充:订阅的时候subscribe()和psubscribe()的第二个参数支持可变参数，也就是可以实现订阅多个频道。
至此实现了两种方式的消息队列:
redis自带的list类型(lpush和rpop或者brpop，rpush和lpop或者blpop)---blpop和brpop是阻塞读取。
"发布/订阅"模式(publish channel message 和 subscribe channel [channel ...] 或者 psubscribe pattern [pattern ...] 通配符订阅多个频道)
补充:
1.发布订阅执行订阅之后该线程处于阻塞状态，线程不会终止，如果终止线程需要退订，需要调用JedisPubSub的unsubscribe()方法
例如:
package plainTest; import cn.xm.redisChat.util.JedisPoolUtils; import redis.clients.jedis.Jedis; import redis.clients.jedis.JedisPubSub; /** * @Author: cc * @Description * @Date: 23:36 2020/10/13 */ public class Test111 { public static void main(String[] args) { Jedis jedis = JedisPoolUtils.getJedis(); System.out.println("订阅前"); jedis.subscribe(new JedisPubSub() { @Override public void onMessage(String channel, String message) { super.onMessage(channel, message); } }, "c1"); System.out.println("订阅后"); } }
结果只会打印订阅前，而且线程不会终止。
为了使线程可以停止，必须退订，而且退订只能调用 JedisPubSub.unsubscribe()方法，例如:收到quit消息之后会退订，线程会回到主线程打印订阅后。
package plainTest; import cn.xm.redisChat.util.JedisPoolUtils; import redis.clients.jedis.Jedis; import redis.clients.jedis.JedisPubSub; /** * @Author: cc * @Description * @Date: 23:36 2020/10/13 */ public class Test111 { public static void main(String[] args) { Jedis jedis = JedisPoolUtils.getJedis(); System.out.println("订阅前"); jedis.subscribe(new JedisPubSub() { @Override public void onMessage(String channel, String message) { if("quit".equals(message)){ unsubscribe("c1"); } System.out.println(message); } @Override public void unsubscribe(String... channels) { super.unsubscribe(channels); } }, "c1"); System.out.println("订阅后"); } }
2.BRPOP:当给定列表内没有任何元素可供弹出的时候，连接将被BRPOP命令阻塞，直到等待超时或发现可弹出元素为止。(每次只弹出一个元素，当没有元素的时候处于阻塞，当弹出一个元素之后就会解除阻塞)
没有元素的时候只会打印brpop之前。
package plainTest; import cn.xm.redisChat.util.JedisPoolUtils; import redis.clients.jedis.Jedis; import java.util.List; /** * @Author: cc * @Description * @Date: 23:36 2020/10/13 */ public class Test111 { public static void main(String[] args) { Jedis jedis = JedisPoolUtils.getJedis(); System.out.println("brpop之前"); List<String> messages = jedis.brpop(0,"list1"); System.out.println(messages); System.out.println("brpop之后"); } }
