Routing a message, means that you can create differents targets for the same queue. The routed-messaging is a sample for how to solve one problem - Load Balancer - when the message needs to reach to a specifc server using ActiveMQ as a message broker.

• ActiveMQ
• Java 1.8+

• mvn clean install

• spring.activemq.broker-url (opcional, default: tcp://localhost:61616)

  • URL to connect to ActiveMQ

• server.port (required, for configure 2 or more servers in same machine for test)

  • The server port (localhost:8080, localhost:8081)

• jms.selector (required)

  • That's is the filter, the message selector, who'll say "I'll pick just the message which have this selector configured"

In this example, I configured three endpoints:

• The default endpoint: localhost:{server.port}
  • This endpoint create a message with a default value 1 in the property called server, with this, when run the server with -Djms.selector=server=1 this server will pick this message to process.
• The endpoint with an id: localhost:{server.port}/{id}
  • This one will create a message with {id} value, with this, when run the server with -Djms.selector=server={id} this server will pick this message to process.

• This application send a message with a integer property with name server (server=1)
• Run an ActiveMQ server
• Create 2 or more instances of this applications (with differents jms.selector and server.port values):
  • java -jar "-Dserver.port=8080" "-Djms.selector=server=1" .\routed-messaging-0.0.1-SNAPSHOT.jar
  • java -jar "-Dserver.port=8081" "-Djms.selector=server=2" .\routed-messaging-0.0.1-SNAPSHOT.jar
• Run the command curl http://localhost:8080/ (or use your preferred tool for http request)
  • A mensage Hello World will be delivered to an instance of server=1
• Run the command curl http://localhost:8080/2 (or use your preferred tool for http request)
  • A mensage Hello World will be delivered to an instance of server=2
• Run the command curl http://localhost:8080/1 (or use your preferred tool for http request)
  • A mensage Hello World will be delivered to an instance of server=1
• Run the command curl http://localhost:8080/2 twice (or use your preferred tool for http request)
  • A mensage Hello World will be delivered to an instance of server=2 twice

Try to send multiple message to the same server id, you'll see the message being delivered to the same server always.

A load balancer manage which server it'll deliver the http request, the server that receives the request will put a message to message broker with the param id, and the server that is configured with a selector with these id will pick the message...

This application doesn't have a load balancer, but notice that I've always send a http request to one instance (with 8080 port), never used the 8081 port and even this, the server with server=2 (port 8081) could pick a message

Note: Message with no id configured will be listened for all instances that are listening the same queue, try to send a message to localhost:8080/all 2 or more times, the servers will intercalate who'll read the message