It manages the requests through the ContainerRequestContext. This context manages different informations as the used language, the input stream, the headers and the security contexts. Here a sample:

public class RegisterCall implements ContainerRequestFilter 
{
   @Override
   public void filter(ContainerRequestContext requestContext) throws IOException {
      String calledMethod = requestContext.getMethod();   
      requestContext.setProperty("calledMethod", calledMethod);
   }
}

This filter adds a property to the request setting the actual method used by the client against the service.