Embed OSGI in war

Question

I am interested in adding an OSGI container into my WAR but I can't find a tutorial or a documentation on how to do this. I found some things that are not useful at all. I am interested in Felix implementation and Atlassian implementation.

I am willing to do this so that my war accepts plug-ins and I can dynamically extend my Web app and also deploy it to any Web server.

Any links to a documentation or something? Any help is appreciated.

Answer 1

Adding an OSGi Framework launcher to a web application is not a big deal.

You need to add a listener to start the framework launcher in your web.xml

<listener>
  <listener-class>at.badgateway.StartupListener</listener-class>
</listener>

The startuplistener could look like this

public class StartupListener implements ServletContextListener {

//vars

    @Override
    public void contextInitialized(ServletContextEvent event) {
        // set props
    Map<String, String> config = new HashMap<String, String>();
    config.put(Constants.FRAMEWORK_STORAGE, "path to cache");
    config.put(Constants.FRAMEWORK_STORAGE_CLEAN, "true");

        try {
                    // get framework and start it
            FrameworkFactory frameworkFactory = ServiceLoader.load(FrameworkFactory.class).iterator().next();
            framework = frameworkFactory.newFramework(config);
            framework.start();

                    // start existing bundles
            bundleContext = framework.getBundleContext();
            starter = new MyBundleStarter(servletContext, bundleContext);
            starter.launch();

        } catch (Exception ex)  
    }

    @Override
    public void contextDestroyed(ServletContextEvent arg0) {
         // stop framework
    }
}

Take care of MyBundlestarter class in the upper quote, it is the class which activates all bundles contained in your war. (e.g. /WEB-INF/Osgi-Bundles)

import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
public class MyBundleStarter{

    private BundleContext bundleContext = null;

    public void launch() throws Exception {

        ArrayList<Bundle> availableBundles= new ArrayList<Bundle>();
        //get and open available bundles
        for (URL url : getBundlesInWar()) {
            Bundle bundle = bundleContext.installBundle(url.getFile(), url.openStream());
            availableBundles.add(bundle);
        }

        //start the bundles
        for (Bundle bundle : availableBundles) {
            try{
            bundle.start();
            }catch()
        }

    private List<URL> getBundlesInWar() throws Exception {
        // returns a list of URLs located at destination
    }
}

Last but not least, you have to add an osgi framework to your project.

    <dependency>
    <groupId>org.apache.felix</groupId>
    <artifactId>org.apache.felix.framework</artifactId>
    </dependency>

or

    <dependency>
        <groupId>org.eclipse.osgi</groupId>
        <artifactId>org.eclipse.osgi</artifactId>
    </dependency>