HornetQ is an open source project to build a multi-protocol, embeddable, very high performance, clustered, asynchronous messaging system.
Why learning another messaging system ? here are a few good reasons:

• Hornet Q is an open source messaging system which can be used as standalone or on any application server or even embedded in your applications.
• HornetQ delivers amazing messaging performance.
• HornetQ provides seamless clustering capabilities.
• Most important for us: it's going to be the default Messaging system in JBoss AS 6.

It takes just a few minutes to be operative, let's start:

Download HornetQ from JBoss.org

http://www.jboss.org/hornetq/downloads.html

Download the latest stable release and unzip in a convenient location.

Start HornetQ

HornetQ can be started in 3 ways:

• 1# Standalone server
• 2# Inside an application server
• 3# Embedded in your applications

#1 Standalone server

Launching HornetQ as standalone server is fairly trivial: reach the "bin" folder in your HornetQ distribution and launch run.bat/run.sh

#2 Inside JBoss AS 4.x-5.x

If you don't want to run HornetQ as standalone but embedded in jBoss AS there's a simple script in the folder HORNETQ-HOME\config\jboss-as named build.bat/build.sh.
The only requirement is to set the JBOSS_HOME environment variable.


This will create two additional JBoss configurations default-with-hornetq and all-with-hornetq. The former can be used to run JBoss as standalone server and the latter as clustered node.

Now launch JBoss AS using the -c parameter. For example:
run -c default-with-hornetq

#3 Embedded in your Java code
 

HornetQ can be started as well in embedded mode. This can be particularly useful for testing purposes if you don't want to start/stop manually the server on your machine.

An example of how to start an embedded HornetQ server is provided in HornetQExample.java file which can be found in the HORNETQ_HOME/examples/common/src/org/hornetq/common/example

Inspect HornetQ configuration

The configuration of HornetQ is split in several files. The following table resumes the basics of its configuration.

File	Content
hornetq-jboss-beans.xml	Micro container configuration file.
hornetq-configuration.xml	Main configuration file. Used to change JMS Storage directories and Message settings.
hornetq-jms.xml	JMS Queue/Topic configuration.
jms-ds.xml	JMS Provider configuration and Connection factory configuration.
login-config.xml	The XML based JAAS login configuration.

As a developer you are likely to be interested to uodate the hornetq-jms.xml file to add/remove new Queue/Topics.

Deploy a simple MDB 

Deploying an MDB is fairly trivial. The only difference with a MDB powered by another JMS provider is the @ResourceAdapter annotation which informs the EJB container to use HornetQ resource adapter configuration.

package com.sample;

import org.jboss.ejb3.annotation.ResourceAdapter;

import javax.ejb.*;
import javax.jms.*;

@MessageDriven(name = "MDBExample",
               activationConfig =
                     {
                        @ActivationConfigProperty(propertyName = "destinationType", propertyValue = "javax.jms.Queue"),
                        @ActivationConfigProperty(propertyName = "destination", propertyValue = "queue/testQueue"),
                     })
 
@ResourceAdapter("hornetq-ra.rar")
public class MDBExample implements MessageListener
{
   public void onMessage(Message message)
   {
      try
      {
         TextMessage textMessage = (TextMessage)message;
 
         String text = textMessage.getText();
         
         System.out.println("message " + text);

      }
      catch (Exception e)
      {
         e.printStackTrace();
      }
   }
}

Ok. In order to test this MDB you have to update your hornetq-jms.xml file (which is located, if you are running HornetQ inside JBoss in deploy\hornetq.sar) by adding the testQueue definition:

<queue name="testQueue">
      <entry name="/queue/testQueue"/>
</queue>

And finally here's a generic test client which can be used to send messages to the "testQueue":

package com.sample;

import java.util.Properties;
import javax.jms.*;
import javax.naming.Context;

public class QueueExample   
{

	public void example() throws Exception
	{
		String destinationName = "queue/testQueue";

		Context ic = null;
		ConnectionFactory cf = null;
		Connection connection =  null;

		try
		{         
			ic = getInitialContext();

			cf = (ConnectionFactory)ic.lookup("/ConnectionFactory");
			Queue queue = (Queue)ic.lookup(destinationName);

			connection = cf.createConnection();
			Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
			MessageProducer publisher = session.createProducer(queue);
			MessageConsumer subscriber = session.createConsumer(queue);

			connection.start();

			TextMessage message = session.createTextMessage("Hello!");
			publisher.send(message);
            System.out.println("Message sent!");
 

		}
		finally
		{         
			if(ic != null)
			{
				try
				{
					ic.close();
				}
				catch(Exception e)
				{
					throw e;
				}
			}

			closeConnection(connection);
		}
	}
	private void closeConnection(Connection con)
	{      
		try
		{
			if (con != null)
			{
				con.close();
			}         
		}
		catch(JMSException jmse)
		{
			System.out.println("Could not close connection " + con +" exception was " + jmse);
		}
	}


	public static void main(String[] args) throws Exception
	{
		new QueueExample().example();
	}
	public static Context getInitialContext( )
	throws javax.naming.NamingException {

		Properties p = new Properties( );
		p.put(Context.INITIAL_CONTEXT_FACTORY,
				"org.jnp.interfaces.NamingContextFactory");
		p.put(Context.URL_PKG_PREFIXES,
		" org.jboss.naming:org.jnp.interfaces");
		p.put(Context.PROVIDER_URL, "jnp://localhost:1099");
		return new javax.naming.InitialContext(p);
	}  
}

Your example is completed. remember to add HornetQ libraries (found in the HORNETQ_HOME/lib) to your client:


References:
http://www.jboss.org/hornetq/docs.html

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