Error running a Maven OSGi project

Question

I'm trying to run a maven OSGi bundle project, but I get:

Exception in thread "main" java.lang.NullPointerException: Specified service reference cannot be null.

at System.out.println(framework.getBundleContext().getService(reference)); below in initialize().

I can't seem to get it right. I'm new to OSGi. Please help me get the project to run. Thank you all in advance.

This is the way I embed my OSGi Framework, then try to start the service:

private void initialize() throws BundleException, URISyntaxException {
    Map<String, String> map = new HashMap<String, String>();

        // make sure the cache is cleaned
    map.put(Constants.FRAMEWORK_STORAGE_CLEAN, Constants.FRAMEWORK_STORAGE_CLEAN_ONFIRSTINIT);

    map.put("ds.showtrace", "true");
    map.put("ds.showerrors", "true");

    FrameworkFactory frameworkFactory = ServiceLoader.load(FrameworkFactory.class).iterator().next();
    Framework framework = frameworkFactory.newFramework(map);

    System.out.println("Starting OSGi Framework");
    framework.init();
    framework.start();

    loadScrBundle(framework);

    framework.getBundleContext().installBundle("file:" + "D:/core-1.0.jar").start();

    ServiceReference<?> reference = framework.getBundleContext()
    .getServiceReference(HelloWorldService.class.getName());
    System.out.println(framework.getBundleContext().getService(reference));

    for (Bundle bundle : framework.getBundleContext().getBundles()) {
        System.out.println("Bundle: " + bundle.getSymbolicName());
        if (bundle.getRegisteredServices() != null) {
            for (ServiceReference<?> serviceReference : bundle.getRegisteredServices())
                System.out.println("\tRegistered service: " + serviceReference);
        }
    }
}

This is how I export the rev.core.api service package:

<build>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>2.0.2</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.felix</groupId>
            <artifactId>maven-bundle-plugin</artifactId>
            <extensions>true</extensions>
            <configuration>
                <instructions>
                    <Bundle-SymbolicName>${project.name}</Bundle-SymbolicName>
                    <Export-Package>rev.core.api</Export-Package>
                    <Bundle-Activator>rev.core.impl.Activator</Bundle-Activator>
                    <Bundle-Vendor>Rev CAIT</Bundle-Vendor>
                </instructions>
            </configuration>
        </plugin>
    </plugins>
</build>

score 1 · Answer 1 · answered Dec 31 '15 at 08:21

I can imagine two causes:

The service is not registered

Are you sure the service is registered? You did not post the code of your activator. Is your service registered in the start method of the Activator?

The service instance implements another HelloworldService type

Is it possible that any of your bundles within the container contains the HelloWorldService type? See the Javadoc of BundleContext.getServiceReference(...):

... and the packages for the class names under which the services were registered match the context bundle's packages as defined in ServiceReference.isAssignableTo(Bundle, String).

If the framework bundle sees another instance of the HelloWorldService type than the bundle that registered the service, the BundleContext.getServiceReference methods of the framework bundle context will not return the reference of the service.

Try calling BundleContext.getAllServiceReferences(...). If that returns a service reference but BundleContext.getServiceReference(...) not, this is your issue.

Error running a Maven OSGi project

1 Answers1

The service is not registered

The service instance implements another HelloworldService type