Distributed OSGi Greeter Demo Walkthrough

This is a walkthrough of the Distributed OSGi Greeter Demo. It should help users of the Distributed OSGi get started with it.

The greeter demo can be found in the samples/greeter directory and implements a simple OSGi Greeter Service and a consumer to that service with a trivial UI.

The Greeter demo design

The demo is composed of 3 bundles:

• The Greeter Interface bundle
• The Greeter Service Implementation bundle
• The Greeter Service Consumer bundle
  The Greeter Interface bundle exports the GreeterService interface which both other bundles depend on. This is the interface:

  public interface GreeterService {
      Map<GreetingPhrase, String> greetMe(String name) throws GreeterException;
  }

  The GreetingPhase and GreeterException classes are also defined by this bundle.

The Server Side

The Greeter Service bundle provides a trivial implementation of the GreeterService interface. Additionally, it has an Activator:

public class Activator implements BundleActivator {
    private ServiceRegistration registration;

    public void start(BundleContext bc) throws Exception {
        Dictionary props = new Hashtable();

        props.put("osgi.remote.interfaces", "*");
        props.put("osgi.remote.configuration.type", "pojo");
        props.put("osgi.remote.configuration.pojo.address", "http://localhost:9090/greeter");
        
        registration = bc.registerService(GreeterService.class.getName(), new GreeterServiceImpl(), props);
    }

    public void stop(BundleContext bc) throws Exception {
        registration.unregister();
    }
}

Besides creating the service instance, the activator sets the additional properties on the service that are required to make it available remotely:

• The osgi.remote.interfaces property is set to '*', which means that all the interfaces passes to registerService are good for remoting. In this case it's just the GreeterService interface.
• The osgi.remote.configuration.type is set to pojo, which is a CXF specific configuration type that can be used to set the URL at which the service is to be exposed. This is done via the osgi.remote.configuration.pojo.address property.

Let's run the server in Felix 1.4.1. As a prerequisite it requires some of the OSGi Compendium Specification interfaces. These don't come with the Felix download but are built as part of the Felix build. When building a distribution, the Felix bundle with these interfaces is pulled in via Maven and put in the target/deps directory.
To set up my Felix environment, I'm running the following commands:

C:\felix-1.4.1>java -jar bin\felix.jar

Welcome to Felix.
=================

-> ps
START LEVEL 1
   ID   State         Level  Name
[   0] [Active     ] [    0] System Bundle (1.4.1)
[   1] [Active     ] [    1] Apache Felix Shell Service (1.0.2)
[   2] [Active     ] [    1] Apache Felix Shell TUI (1.0.2)
[   3] [Active     ] [    1] Apache Felix Bundle Repository (1.2.1)
-> start file:/<dosgi-root>/distribution/single-bundle/target/deps/org.osgi.compendium-1.2.0.jar
-> start file:/<dosgi-root>/distribution/single-bundle/target/cxf-dosgi-ri-singlebundle-distribution-1.0-SNAPSHOT.jar

Some log meesages may come up now.
Note that instead of manually adding these bundles to the Felix container, you can also append the target/felix.config.properties.append file to the <felix-root>/conf/config.properties file. This will automatically load these two bundles when Felix starts up.

Now let's start up the server-side greeter bundles.

-> start file:/<dosgi-root>/samples/greeter/interface/target/cxf-dosgi-ri-samples-greeter-interface-1.0-SNAPSHOT.jar
-> start file:/<dosgi-root>/samples/greeter/impl/target/cxf-dosgi-ri-samples-greeter-impl-1.0-SNAPSHOT.jar
-> ps
START LEVEL 1
   ID   State         Level  Name
[   0] [Active     ] [    0] System Bundle (1.4.1)
[   1] [Active     ] [    1] Apache Felix Shell Service (1.0.2)
[   2] [Active     ] [    1] Apache Felix Shell TUI (1.0.2)
[   3] [Active     ] [    1] Apache Felix Bundle Repository (1.2.1)
[   4] [Active     ] [    1] OSGi R4 Compendium Bundle (4.1.0)
[   5] [Active     ] [    1] Distributed OSGi Distribution Software Single-Bundle Distribution
[   8] [Active     ] [    1] CXF Distributed OSGi Greeter Demo Interface Bundle
[   9] [Active     ] [    1] CXF Distributed OSGi Greeter Demo Service Implementation Bundle

Some more log messages come up. When it says INFO: Remote org.apache.cxf.dosgi.samples.greeter.GreeterService endpoint has been published into Discovery service you know that the service is exposed remotely, and you can verify this by requesting the WSDL:

The Service Consumer side.