RABBITMQ Example Tutorial: Theme Switches

In the previous example, although we used direct routing instead of fanout routing to solve the problem of blind broadcast, direct routing has its drawbacks, and he cannot route forward based on multiple criteria.

In the above log system, if not only want to make a subscription based on the log level, but also want to make a subscription based on the source of the log to do what? At this point you may think of the Syslog Service in UNIX system Tools, which is based not only on the log level (Info/warn/crit ... ) will also be routed according to the operation (Auth/cron/kern ... ) to do route forwarding.

In that case, the log system is much more flexible, not only to listen for critical errors from ' cron ', but also to listen to all the logs from ' Kern '. In fact, the subject switch (topic Exchange) can solve this problem.

　　Subject switch (Topic Exchange)

The routing code for a theme switch cannot be arbitrary and must be a list of words separated by small tree points. These words can be written casually, but they are usually words related to the characteristics of the connection message. The effective route code should be such as "Stock.usd.nyse", "NYSE.VMW", "Quick.orange.rabbit". The routing code can be written casually, but the length is limited to 255 bytes.

Note that the binding code must also be in the same form. A topic switch is similar to a direct switch-a message with a specific routing code is routed to all matching binding code queues, but there are two special binding codes:

*: It can replace a word

#: It can replace 0 or more words

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In this example, we send messages to all animals that correspond to three words (the first word describes the speed; the second word describes the color; the third word describes the species) the routing code that makes up the message: "<speed>.<colour>.< Species> ".

We created three bindings: Q1 uses "*.orange.*" bindings, Q2 uses "*.*.rabbit" and "lazy.#" bindings. The meanings of these bindings are as follows:

Q1 describes all animals with orange color.

Q2 describes the animals that are rabbits and the lazy animals.

In this way, the "quick.orange.rabbit" message is forwarded to the Q1, Q2 two queues through the route. The "lazy.orange.elephant" message is also forwarded to the Q1, Q2 two queues. The "Quick.orange.fox" message will only be forwarded to the Q1 queue, and "Lazy.brown.fox" will only be forwarded to the Q2 queue. "Lazy.pink.rabbit" is forwarded to the Q2 queue once, although it matches two bindings. "Quick.brown.fox" does not match any one queue will be discarded.

If we break the rules and only send one or four words at a time, such as "orange" or "quick.orange.male.rabbit", these messages do not match any bindings and will be discarded. However, if a message such as "Lazy.orange.male.rabbit" is sent, it will still be forwarded to the Q2 queue because it matches the final binding.

The theme switch is a very powerful switch, and when it binds only "#", it will receive all messages, similar to the fanout switch. When the "*" and "#" symbols are not used, the role of the subject switch is equivalent to the direct switch.

　　Source

Emitlogtopic.java

package com.favccxx.favrabbit;import com.rabbitmq.client.channel;import  com.rabbitmq.client.connection;import com.rabbitmq.client.connectionfactory;public class  emitlogtopic {private static final string exchange_name =  "Topic_logs"; Public static void main (STRING[]&NBSP;ARGV)  {Connection connection = null; channel channel = null;try {connectionfactory factory = new  ConnectionFactory (); Factory.sethost ("localhost"); connection = factory.newconnection (); channel =  connection.createchannel (); Channel.exchangedeclare (exchange_name,  "topic"); string[] routingkeys = {  "Fast.orange.duck",  "Slow.orange.fish",  "Grey.rabbit",   "Fast.black.rabbit", "Quick.white.rabbit",  "Lazy.dog",  "Lazy.black.pig"  }; string[] messages = {  "Hello",  "Guys",  "Girls",  "babies" &nbsP;}; for  (int i = 0; i < routingkeys.length; i++)  {for  (int  j = 0; j < messages.length; j++)  {channel.basicpublish (EXCHANGE_ Name, routingkeys[i], null, messages[j].getbytes ("UTF-8")); System.out.println (" [x] Sent " " + routingKeys[i] + " ': ' " +  messages[j] +  "'");}}}  catch  (exception e)  {e.printstacktrace ();}  finally {if  (Connection != null)  {try {connection.close ();}  catch  (Exception ignore)  {}}}}

Receivelogstopic.java

Package com.favccxx.favrabbit;import java.io.ioexception;import com.rabbitmq.client.amqp;import  com.rabbitmq.client.Channel;import com.rabbitmq.client.Connection;import  com.rabbitmq.client.connectionfactory;import com.rabbitmq.client.consumer;import  com.rabbitmq.client.defaultconsumer;import com.rabbitmq.client.envelope;public class  receivelogstopic {private static final string exchange_name =  "Topic_logs"; Public static void main (STRING[] ARGV)  throws exception {connectionfactory  factory = new connectionfactory (); Factory.sethost ("localhost"); Connection connection = factory.newconnection (); Channel channel = connection.createchannel (); Channel.exchangedeclare (EXCHANGE_NAME,  "topic "); String queuename = channel.queuedeclare (). Getqueue (); string[] bindingkeys = {  "*.orange.*",  " *.*.rabbit ", " lazy.# " };for  (Final string bindingkey : bindingkeys)  { Channel.queuebind (Queuename, exchange_name, bindingkey); Consumer consumer = new defaultconsumer (channel)  {@Overridepublic  void  Handledelivery (STRING CONSUMERTAG, ENVELOPE ENVELOPE, AMQP. Basicproperties properties,byte[] body)  throws IOException {String message  = new string (body,  "UTF-8"); System.out.println ("["  + bindingKey +  "] RECEIVED MESSAGE : '"  +  message +  "'  from routingKey : "  + envelope.getroutingkey ());}; Channel.basicconsume (Queuename, true, consumer);}}}

Run the message sender in the message receiving platform output content as follows

[*.orange.*] received message : ' Hello '  from routingkey : fast.orange.duck[* . *.rabbit] received message : ' Guys '  from routingkey : fast.orange.duck[lazy . #] received message : ' Girls '  from routingkey : fast.orange.duck[*.orange.* ] received message : ' Babies '  from routingkey : fast.orange.duck[*.*.rabbit]  RECEIVED MESSAGE&NBSP: ' Hello '  from routingKey : slow.orange.fish[lazy.#]  RECEIVED MESSAGE&NBSP: ' Guys '  from routingKey : slow.orange.fish[*.orange.*]  RECEIVED MESSAGE&NBSP: ' Girls '  from routingKey : slow.orange.fish[*.*.rabbit]  RECEIVED MESSAGE&NBSP: ' Babies '  from routingKey : slow.orange.fish[lazy.#]  RECEIVED MESSAGE&NBSP: ' Hello '  from routingKey : fast.black.rabbit[*.orange.*]  Received message : ' Guys '  from routingkey : fast.black.rabbit[*.*.rabbit] received message  : ' Girls '  from routingkey : fast.black.rabbit[lazy.#] received message  : ' Babies '  from routingkey : fast.black.rabbit[*.orange.*] received message  : ' Hello '  from routingkey : quick.white.rabbit[*.*.rabbit] received message  : ' Guys '  from routingkey : quick.white.rabbit[lazy.#] received message  : ' Girls '  from routingkey : quick.white.rabbit[*.orange.*] received message &NBSP: ' Babies '  from routingKey : quick.white.rabbit[*.*.rabbit] Received  message : ' Hello '  from routingkey : lazy.dog[lazy.#] received message : ' Guys '  from routingkey : lazy.dog[*.orange.*] received message : ' Girls '  from routingKey :  lazy.dog[*.*.rabbit] received message : ' Babies '  from routingKey :  lazy.dog[lazy.#] received message : ' Hello '  from routingkey : lazy.black.pig [*.orange.*] received message : ' Guys '  from routingkey : lazy.black.pig[*.*. rabbit] received message : ' Girls '  from routingkey : lazy.black.pig[lazy.#]  received message : ' Babies '  from routingkey : lazy.black.pig

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RABBITMQ Example Tutorial: Theme Switches