OSGi Event Admin with Spring DM

In my current post, I will try to highlight using event admin with spring DM. By an example, we will send an event inside the OSGi container from a notifier bundle and intercept by second subscriber bundle.

1 - Notifier Bundle

•  It contains a single Activator class.

•  Get an Event Admin service.

•  Send an event every 30 seconds.

•  An event is according to JTUNISIe queue and containing the current step and time stamp.

package com.jtunisie.osgi.event.notifier.impl;

import java.util.Date;
import java.util.Properties;
import org.osgi.service.event.Event;
import org.osgi.service.event.EventAdmin;
import org.springframework.osgi.extensions.annotation.ServiceReference;

public class Activator {

    private String EVENT_QUEUE;

    protected void init() throws InterruptedException {
        Properties props = new Properties();
        int i=0;
        while (true) {
            props.setProperty("property", ""+i+++" : "+ new Date());
            eventAdmin.sendEvent(new Event(EVENT_QUEUE, props));
            Thread.sleep(30*1000);
        }
    }
    private EventAdmin eventAdmin;

    @ServiceReference
    public void setEventAdmin(EventAdmin eventAdmin) {
        this.eventAdmin = eventAdmin;
    }

    public void setEVENT_QUEUE(String EVENT_QUEUE) {
        this.EVENT_QUEUE = EVENT_QUEUE;
    }
}

 On the spring config file we just call the init method after bundle starting :

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:osgi="http://www.springframework.org/schema/osgi"
  xsi:schemaLocation="http://www.springframework.org/schema/beans
  http://www.springframework.org/schema/beans/spring-beans.xsd
  http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi.xsd"
  >

    <bean id="activator" class="com.jtunisie.osgi.event.notifier.impl.Activator" init-method="init">
        <property name="EVENT_QUEUE" value="JTUNISE"/>
    </bean>
   
    <bean class="org.springframework.osgi.extensions.annotation.ServiceReferenceInjectionBeanPostProcessor"/>
</beans>

2 -  Subscriber Bundle

•  Contains a single Activator class

•  Implements EventHandler Interface

•  When an event is intercepted it prints the new property.

package com.jtunisie.osgi.event.subscriber.impl;

import org.osgi.service.event.Event;
import org.osgi.service.event.EventHandler;

/**
 *
 * @author slim
 */
public class Activator implements EventHandler {

    private String property;

    @Override
    public void handleEvent(Event event) {

        String value = event.getProperty(property).toString();
        System.out.println("value : " + value);
    }

    public void setProperty(String property) {
        this.property = property;
    }
}

Spring DM helps us to register our bundle as an event hander service and setting it to listen jtunisie queue.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xmlns:osgi="http://www.springframework.org/schema/osgi"
  xmlns:osgix="http://www.springframework.org/schema/osgi-compendium"
  xmlns:context="http://www.springframework.org/schema/context"
  xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
  http://www.springframework.org/schema/context     http://www.springframework.org/schema/context/spring-context-2.5.xsd
  http://www.springframework.org/schema/osgi-compendium http://www.springframework.org/schema/osgi-compendium/spring-osgi-compendium.xsd
  http://www.springframework.org/schema/osgi http://www.springframework.org/schema/osgi/spring-osgi.xsd"
  >
 

    <bean id="activator" class="com.jtunisie.osgi.event.subscriber.impl.Activator">
        <property name="property" value="property"/>
    </bean>

  <osgi:service id="activatorService" ref="activator" interface="org.osgi.service.event.EventHandler">
        <osgi:service-properties>
           <entry key="event.topics" value="JTUNISE"/>
        </osgi:service-properties>
    </osgi:service>


</beans>

3- Deployment

- Project is composed of one Maven project with two sub projects using Felix plug-in.
- At the deployment level we need :
   1- An OSGi container.
   2- Spring dependencies ( Extenders, beans ...) with spring-osgi-annotations

After installing the two bundles, the output should be the same as :

osgi> value : 1 : Tue Nov 11 23:57:33 CET 2008
value : 2 : Tue Nov 11 23:58:03 CET 2008
value : 3 : Tue Nov 11 23:58:33 CET 2008
value : 4 : Tue Nov 11 23:59:03 CET 2008
value : 5 : Tue Nov 11 23:59:33 CET 2008
value : 6 : Wed Nov 12 00:00:03 CET 2008
value : 7 : Wed Nov 12 00:00:33 CET 2008
value : 8 : Wed Nov 12 00:01:03 CET 2008
value : 9 : Wed Nov 12 00:01:33 CET 2008
value : 10 : Wed Nov 12 00:02:03 CET 2008
value : 11 : Wed Nov 12 00:02:33 CET 2008
value : 12 : Wed Nov 12 00:03:03 CET 2008
value : 13 : Wed Nov 12 00:03:33 CET 2008
value : 14 : Wed Nov 12 00:04:03 CET 2008

Note : source code is under svn : svn checkout http://osgievent.googlecode.com/svn/trunk/ osgievent-read-only