ActiveMQ Message Consumer in Spring

In the last blog we saw how to configure an ActiveMQ broker to run in a Spring environment. In this blog we will see how to configure a message consumer. Again, I am not trying to explain how consumers work but just sharing code and config to make it work in Spring :p

Since we have the luxury of Spring , we will use a message listener container provided by the framework: SimpleMessageListenerContainer (org.springframework.jms.listener.SimpleMessageListenerContainer ). My needs were simple and non-transactional so this container suffices

The basic reason is the desire to be message driven i.e. I want my app to take some actions as and when it receives messages. The container bean definition should look like:

    <bean id="jmsContainer" class="org.springframework.jms.listener.SimpleMessageListenerContainer">

        <property name="autoStartup" value="true"/>

        <property name="connectionFactory" ref="myConnectionFactory"/>

        <property name="destination" ref="myDestination"/>

        <property name="messageListener" ref="myMessageListener"/>

        <property name="acceptMessagesWhileStopping" value="true"/>

    </bean>

This config makes the container start when the bean gets loaded and makes sure no messages are lost even if it is down. Further we need to specify the connection factory to use to connect to broker, the destination at broker from which we wish to hear and the message listener that ultimately handles the message. The config for these three will look like:

 <bean id="myDestination" class="org.apache.activemq.command.ActiveMQQueue">

        <constructor-arg value="myPackage.myQueue"/>

    </bean>

 <bean id="myConnectionFactory" class="org.apache.activemq.ActiveMQConnectionFactory">

        <property name="brokerURL" value="tcp://localhost:61636"/>

   </bean>

<bean id="myMessageListener" class="myPackage.MyMessageListener">       

    <property name="appName" value="My Application"/>

</bean>

Destination takes the name for destination in order to identify it at broker. the producer would refer it by the same name. JNDI can be used for more sophisticated look-ups which we may see some other time. Connection factory just needs url for a running broker. Message Listener is just our custom bean to handle messages. MyMessageListener would look like:

package myPackage;

import javax.jms.*;

public class MyMessageListener implements MessageListener {

    private String appName;

    public void setAppName(String appName){

        this.appName = appName;    

    }

    public void onMessage(Message message) {

        //do your stuff

    }

}

Finally, don't forget the POM dependencies included in last blog if you are using Maven. You should be good to go.