How to add services to desktop Apache Felix application

Question

I'm new to Apache Felix. I want to create simple Desktop application based on Apache Felix framework. I found this simple example how to create simple main method which starts the framework as application but I'm not aware how to add services to the application.

package com.paint.servicebased;

import java.util.Map;
import java.util.ServiceLoader;

import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;
import org.osgi.framework.BundleException;
import org.osgi.framework.launch.Framework;
import org.osgi.framework.launch.FrameworkFactory;

/**
 * This class provides a static {@code main()} method so that the bundle can be
 * run as a stand-alone host application. In such a scenario, the application
 * creates its own embedded OSGi framework instance and interacts with the
 * internal extensions to providing drawing functionality. To successfully
 * launch the stand-alone application, it must be run from this bundle's
 * installation directory using "{@code java -jar}". The locations of any
 * additional extensions that have to be started, have to be passed as command
 * line arguments to this method.
 */
public class Application
{

    private static Framework m_framework = null;

    /**
     * Enables the bundle to run as a stand-alone application. When this static
     * {@code main()} method is invoked, the application creates its own
     * embedded OSGi framework instance and interacts with the internal
     * extensions to provide drawing functionality. To successfully launch as a
     * stand-alone application, this method should be invoked from the bundle's
     * installation directory using "{@code java -jar}". The location of any
     * extension that shall be installed can be passed as parameters.
     * <p>
     * For example if you build the bundles inside your workspace, maven will
     * create a target directory in every project. To start the application from
     * within your IDE you should pass:
     * <p>
     *
     * <pre>
     * {@code file:../servicebased.circle/target/servicebased.circle-1.0.0.jar
     * file:../servicebased.square/target/servicebased.square-1.0.0.jar
     * file:../servicebased.triangle/target/servicebased.triangle-1.0.0.jar}
     * </pre>
     *
     * @param args The locations of additional bundles to start.
     *
     */
    public static void main(String[] args)
    {
        // Args should never be null if the application is run from the command
        // line.
        // Check it anyway.
        String[] locations = args != null ? args : new String[0];

        // Print welcome banner.
        System.out.println("\nWelcome to My Launcher");
        System.out.println("======================\n");

        try
        {
            Map<String, String> config = ConfigUtil.createConfig();
            m_framework = createFramework(config);
            m_framework.init();
            m_framework.start();
            installAndStartBundles(locations);
            m_framework.waitForStop(0);
            System.exit(0);
        }
        catch (Exception ex)
        {
            System.err.println("Could not create framework: " + ex);
            ex.printStackTrace();
            System.exit(-1);
        }
    }

    /**
     * Util method for creating an embedded Framework. Tries to create a
     * {@link FrameworkFactory} which is then be used to create the framework.
     *
     * @param config the configuration to create the framework with
     * @return a Framework with the given configuration
     */
    private static Framework createFramework(Map<String, String> config)
    {
        ServiceLoader<FrameworkFactory> factoryLoader = ServiceLoader
                .load(FrameworkFactory.class);
        for (FrameworkFactory factory : factoryLoader)
        {
            return factory.newFramework(config);
        }
        throw new IllegalStateException(
                "Unable to load FrameworkFactory service.");
    }

    /**
     * Installs and starts all bundles used by the application. Therefore the
     * host bundle will be started. The locations of extensions for the host
     * bundle can be passed in as parameters.
     *
     * @param bundleLocations the locations where extension for the host bundle
     * are located. Must not be {@code null}!
     * @throws BundleException if something went wrong while installing or
     * starting the bundles.
     */
    private static void installAndStartBundles(String... bundleLocations)
            throws BundleException
    {
        BundleContext bundleContext = m_framework.getBundleContext();
        Activator hostActivator = new Activator();
        hostActivator.start(bundleContext);
        for (String location : bundleLocations)
        {
            Bundle addition = bundleContext.installBundle(location);
            addition.start();
        }
    }
}

How I can add service which is located in external JAR file and use it into the main jar file which will be used to start the application?

Answer 1

I've got a getting started video that explains services and service dynamics. In the video you also see how to use BndTools (which I highly recommend). For registering and consuming services we use Apache Felix DependencyManager.