Own ResourceHandler to stream images from DB

I'm strugging with my own resource-implementation. The getInputStream-method doesn't get called.

My handler:

public class ResourceHandlerWrapperImpl extends
        ResourceHandlerWrapper {

  private final ResourceHandler wrapped;

  public ResourceHandlerWrapper(final ResourceHandler wrapped)
  {
    this.wrapped = wrapped;
  }

  @Override
  public ResourceHandler getWrapped()
  {
    return wrapped;
  }

  @Override
  public Resource createResource(final String resourceName, final String libraryName)
  {
    if (AppConstants.RESOURCE_MEDIA_LIB.equals(libraryName))
    {
      return new MediaResource(resourceName);
    }
    else
    {
      return super.createResource(resourceName, libraryName);
    }
  }

  /**
   * @see javax.faces.application.ResourceHandlerWrapper#libraryExists(java.lang.String)
   */
  @Override
  public boolean libraryExists(final String libraryName)
  {
    if (AppConstants.RESOURCE_MEDIA_LIB.equals(libraryName))
    {
      return true;
    }
    else
    {
      return super.libraryExists(libraryName);
    }
  }

  /**
   * @see javax.faces.application.ResourceHandlerWrapper#isResourceRequest(javax.faces.context.FacesContext)
   */
  @Override
  public boolean isResourceRequest(final FacesContext context)
  {
    return super.isResourceRequest(context);
  }

}

My resource implementation:

public class MediaResource extends Resource {

    private final String mediaId;

    public MediaResource(final String mediaId) {
        setLibraryName(AppConstants.RESOURCE_MEDIA_LIB);
        setResourceName(mediaId);
        setContentType("image/png");
        this.mediaId = mediaId;
    }

    @Override
    public InputStream getInputStream() throws IOException {
        if (mediaId != null) {
            System.out.println("Yeahhh!!!");
        }

        return null;
    }

    @Override
    public Map<String, String> getResponseHeaders() {