Java OSGi Tutorial for Beginners

Instroduction
Create OSGi "MathConsumer"
Create OSGi "MathService"
Configure MathConsumer use OSGi MathService

1. Instroduction

This document is based on:

Eclipse 4.4 (LUNA)

Here are the steps in the tutorial:

2. Create OSGi "MathConsumer"

No ADS

Create Project MathConsumer

org.o7planning.tutorial.helloosgi.mathconsumer.Activator

This is image after Project was created .

Open class Activator to edit the code:

Activator.java

package org.o7planning.tutorial.helloosgi.mathconsumer;

import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

public class Activator implements BundleActivator {

   private static BundleContext context;

   static BundleContext getContext() {
       return context;
   }

   public void start(BundleContext bundleContext) throws Exception {
       Activator.context = bundleContext;
       System.out.println("MathConsumer Starting...");

       System.out.println("MathConsumer Started");
   }

   public void stop(BundleContext bundleContext) throws Exception {
       Activator.context = null;
       System.out.println("MathConsumer Stopped");
   }

}

Configure the dependency bundles for MathConsumer

MathConsumer is an OSGi also known as a Bundle. Now we will declare MathConsumer using some other Bundle, purpose to be able to run MathConsumer later.

org.eclipse.osgi
org.eclipse.equinox.console
org.apache.felix.gogo.command
org.apache.felix.gogo.runtime
org.apache.felix.gogo.shell

Configuring Eclipse to run MathConsumer

Here we will configure to run directly MathConsumer in Eclipse

Right-click on Project MathService and select "Run As / Run Configuration .."

Enter name:

Run OSGi MathConsumer

Running MathConsumer

This is the result of running OSGi MathConsumer

Using the OSGi command ss to see what is running, and their status.

As we see in illustrations, the ID of OSGi MathConsumer is 2, use the command "stop" to stop this Bundle.

And use the "start" to rerun this OSGi.

3. Create OSGi "MathService"

No ADS

Create Project "MathService"

In Eclipse select:

File/New/Other

Select the type of OSGi is Standard

MathService

org.o7planning.tutorial.helloosgi.Activator

This is project image has been created:

Code Project MathService &register MathService serivce

We will add some class to get the final image of the Project as follows:

MathService.java

package org.o7planning.tutorial.helloosgi.mathservice;

public interface MathService {

   public int sum(int a, int b);

}

MathServiceImpl.java

package org.o7planning.tutorial.helloosgi.mathservice.impl;

import org.o7planning.tutorial.helloosgi.mathservice.MathService;

public class MathServiceImpl implements MathService {

   @Override
   public int sum(int a, int b) {
       return a+ b;
   }

}

MathUtils.java

package org.o7planning.tutorial.helloosgi.utils;

public class MathUtils {

   
   public static int minus(int a, int b)  {
       return a- b;
   }
}

And here is an overview picture of class relations have created.

Activator.java

package org.o7planning.tutorial.helloosgi;

import org.o7planning.tutorial.helloosgi.mathservice.MathService;
import org.o7planning.tutorial.helloosgi.mathservice.impl.MathServiceImpl;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;

public class Activator implements BundleActivator {

   private static BundleContext context;

   static BundleContext getContext() {
       return context;
   }

   public void start(BundleContext bundleContext) throws Exception {
       Activator.context = bundleContext;
       
       System.out.println("Registry Service MathService...");
       
       this.registryMathService();
       
       System.out.println("OSGi MathService Started");
   }

   private void registryMathService() {
       MathService service = new MathServiceImpl();
       context.registerService(MathService.class, service, null);
   }

   public void stop(BundleContext bundleContext) throws Exception {
       Activator.context = null;
       System.out.println("OSGi MathService Stopped!");
   }

}

Configure OSGi MathService and Explains

We configure to export 2 packages org.o7planning.tutorial.helloosgi.utils and org.o7planning.tutorial.helloosgi.mathservice. OSGi is like a closed box, the other OSGi can only use the class/interface is inside the package is exported to the outside.

The following figure illustrates OSGi MathService export 2 package:

org.o7planning.tutorial.helloosgi.mathservice
org.o7planning.tutorial.helloosgi.utils

OSGi MathConsumer can only use the class/interface located in the export package of the MathService.

4. Configure MathConsumer use OSGi MathService

No ADS

Next we will configure to MathConsumer can use OSGi MathService.

Edit class Activator:

Activator.java

package org.o7planning.tutorial.helloosgi.mathconsumer;

import org.o7planning.tutorial.helloosgi.mathservice.MathService;
import org.o7planning.tutorial.helloosgi.utils.MathUtils;
import org.osgi.framework.BundleActivator;
import org.osgi.framework.BundleContext;
import org.osgi.framework.ServiceReference;

public class Activator implements BundleActivator {

    private static BundleContext context;

    static BundleContext getContext() {
        return context;
    }

    public void start(BundleContext bundleContext) throws Exception {
        Activator.context = bundleContext;
        System.out.println("MathConsumer Starting...");

        System.out.println("5-3 = " + MathUtils.minus(5, 3));

        //
        ServiceReference<?> serviceReference = context
                .getServiceReference(MathService.class);
        MathService service = (MathService) context
                .getService(serviceReference);

        System.out.println("5+3 = " + service.sum(5, 3));

        System.out.println("MathConsumer Started");
    }

    public void stop(BundleContext bundleContext) throws Exception {
        Activator.context = null;
        System.out.println("MathConsumer Stopped");
    }

}

Reconfigured to run OSGi MathConsumer

Right-click on the Project MathConsumer select "Run As / Run Configuration .."

No ADS

Java OSGi Tutorial for Beginners

1. Instroduction

2. Create OSGi "MathConsumer"

3. Create OSGi "MathService"

4. Configure MathConsumer use OSGi MathService

Eclipse Technology

Eclipse Technology

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