OSGi Declarative Services - NullPointer Exception

I have a problem with my Declarative Services. I have 2 bundles, one is a server provider and another the user interface that consumes the service.

On server side, the implementation is:

public boolean checkUser(){
    return true;
}

And the XML file inside OSGi-INF folder:

<component name="ZBService">
<implementation class="service.ZBService" />
   <service>
     <provide interface="service.IZBService" />
   </service>
</component>

On client side, the implementation is:

public class GreetingServiceImpl extends RemoteServiceServlet implements GreetingService{
   IZBService zb;

   public void setZBService(IZBService eventAdmin) {
      this.zb = eventAdmin;
   }

   public void unsetZBService(IZBService eventAdmin){
      if(this.zb == eventAdmin){
          this.zb = null;}
   }
   public boolean greetServer(String input, String input2) throws Exception {
      return zb.checkUser();
   }
}

And XML file:

<component name="ZBService">
  <implementation class="main.java.com.gwt.app.server.GreetingServiceImpl" />
   <service>
        <provide interface="main.java.com.gwt.app.client.GreetingService"/>
   </service>
   <reference name="zb" interface="service.IZBService" bind="setZBService" unbind="unsetZBService" cardinality="0..n" policy="dynamic" />
</component>

Also, I have included the tag Service-Component on manifest file and I have deployed the equinox ds bundle that is ACTIVE.

The client is a GWT user interface, then I inject the service reference into server side of GWT. Well, when I deploy the application on Equinox it runs, but when I push the button, I launch an event to call ZBService. I have debugged the application and the error is zb attribute is null. It is to say, the dependence is nos injected. However the services are exposed on Equinox. If I write services on Equinox console, the services are deployed. Then, my conclusion is the error is due to the injection does not perform.

I would like to know if someone knows what is the reason??

Thanks a lot in advance!!

Nice day

EDIT:

I did your suggestions but it doesn't run. I change the component names and condinality/policy. The result is the same --> NullPointerException due to the injection isn't done.

Also I have debug the application to see if the methods bind and/or unbind are called, but they aren't.

The complete class is:

public class GreetingServiceImpl extends RemoteServiceServlet implements GreetingService{
static protected IZBService zb;

public GreetingServiceImpl(){
    System.out.println("Constructor GreetingServiceImpl");
}

public IZBService getZb() {
    return zb;
}

public void setZb(IZBService zb) {
    GreetingServiceImpl.zb = zb;
}

public void unsetZb(IZBService zb) {
    GreetingServiceImpl.zb = zb;
}

@Override
protected void service(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {
    // Cache the current thread
    Thread currentThread = Thread.currentThread();
    // We are going to swap the class loader
    ClassLoader oldContextClassLoader = currentThread.getContextClassLoader();
    currentThread.setContextClassLoader(this.getClass().getClassLoader());
    super.service(req, resp);
    currentThread.setContextClassLoader(oldContextClassLoader);
}

public void activate(ComponentContext context) {
    System.out.println("Creating new greeter for " + context.getProperties().get("name")
            + ": " + context.getComponentInstance().toString());
}

public void activate() {
    System.out.println("Activando la referencia al servicio");
}

public void deactivate(ComponentContext context) {
    System.out.println("Deactivating greeter for " + context.getProperties().get("name")
            + ": " + context.getComponentInstance().toString());
}

public boolean greetServer(String input, String input2) throws Exception {
    return zb.checkUser();
}
}

And the XML client is:

<?xml version="1.0" encoding="UTF-8" ?>
<scr:component name="serviceZB" xmlns:scr="http://www.osgi.org/xmlns/scr/v1.1.0">
<implementation class="main.j开发者_JAVA百科ava.com.gwt.app.server.GreetingServiceImpl" />
<!-- <service>
    <provide interface="main.java.com.gwt.app.client.GreetingService"/>
</service> -->
<reference name="zb" interface="service.IZBService"
    bind="setZb" unbind="unsetZb" cardinality="1..1"
    policy="static" />
</scr:component>

Why isn't the service injected if the service is deployed???

Here is a list of things you can try:

• First, remove the "static" of zb, that could be the problem.
• If you are using Equinox, add the -Dequinox.ds.print=true flag to the VM arguments and see more information about parsing XMLs and so
• Of course, add sysouts to setZB and unsetZB :)
• Remember that IZBService implementation needs a constructor without arguments
• If you are using Equinox use the "list -c" command to obtain information of each component (it's cool because says exactly why a component is not registered).
• Set the "inmediate=true" in XMLs to force to inmediatly activation.

You have both components with the same name, , which is kind of awkward when discussing them.

The reference on the client side has: cardinality="0..n" policy="dynamic". Which means it can be activated with zero to n references. Yet your code does not handle this. It seems to expect exactly one reference. Perhaps you should use cardinality="1..1" policy="static".