Question

I’m trying to start a Wicket Application using Felix implementation of OSGi HTTP service, for that I just register the service using WicketServlet with applicationClassName parameter:

props.put("applicationClassName", MainApplication.class.getName());
service = (HttpService)context.getService(httpReference);
service.registerServlet("/", new WicketServlet(), props, null);

I have also tried using Felix Whiteboard implementation and registering the web service as a Servlet one:

props.put("alias", "/");
props.put("init.applicationClassName", MainApplication.class.getName());
registration = context.registerService(Servlet.class.getName(), new WicketServlet(), props);

In both cases it fails when I deploy it using Pax Runner and Felix (mvn package install pax:run -Dframework=felix -Dprofiles=log,config), the exception seems to be related with the ClassLoader:

[Jetty HTTP Service] ERROR org.apache.felix.http.whiteboard - Failed to register servlet
org.apache.wicket.WicketRuntimeException: Unable to create application of class es.warp.sample.HTTPLocalGUI.MainApplication
....
....
at java.lang.ClassLoader.loadClass(ClassLoader.java:252)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:247)
....
....

I have tried to export everything in the bundle and it does the same.

The strangest thing is that it works perfectly if I deploy it using Equinox (mvn package install pax:run -Dframework=felix -Dprofiles=log,config).

It seems to be a visibilty issue, but I don’t know how to fix it, am I doing something wrong? Should I try to extend WicketServlet to take control on the instantiation of the application? Or maybe using an application Factory?

Update: Or maybe using an application Factory?

I tried to set the parameter applicationFactoryClassName to ContextParamWebApplicationFactory.class.getName() it and didn’t help, still failing with felix and working with equinox.

Any light is welcomed.

Answer 1

The problem here is that Wicket seems to load the applicationClass badly. I have not looked at the code that does this, but I suspect it’s using current thread’s context classloader.

I did the following to overcome this:

1. Create my own WicketFilter (called MyWicketFilter) and override getClassLoader. This returns this.getClass().getClassLoader().
2. Register the MyWicketFilter as a Filter service to be picked up by the whiteboard http service.

Code for activator start:

Hashtable<String, String> props = new Hashtable<String, String>();
props.put("pattern", "/.*");
props.put("init.applicationClassName", MyApplication.class.getName());

final MyWicketFilter service = new MyWicketFilter();
context.registerService(Filter.class.getName(), service, props);

Code for MyWicketFilter:

public final class MyWicketFilter
    extends WicketFilter
{
    @Override
    protected ClassLoader getClassLoader()
    {
        return this.getClass().getClassLoader();
    }
}

You can also use WicketServlet, but this involves overriding
newWicketFilter and return MyWicketFilter from here.