@Override
public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
    // Call the common handler function that we use for both GET and POST calls.
    logger.info("POST received”);
    handleRequest(request, response);
}

private void handleRequest(HttpServletRequest request, HttpServletResponse response) throws IOException {
    // Get the GitHub event name from the request headers.
    String webhookName = "X-GitHub-Event";
    String webhookValue = request.getHeader(webhookName);
    logger.info("GitHub webhook event: " + webhookValue);

    try {
        switch (webhookValue) {
            case "push":
                // If it is a "push" request we just need to pass it on to the standard integration.
                doPush(request, response);
                break;

            default:
                // The webhook request isn't one we currently handle so we can just send a HTTP 417
                // response code back as the standard  hooks do.
                logger.error("Invalid event type: " + webhookValue);
                response.setStatus(HttpServletResponse.SC_EXPECTATION_FAILED);
        }
    }

    catch (NullPointerException ex) {
        // This isn't a GitHub event so we can just log an error and return.
        logger.error("X-GitHub-Event not found!");
    }
}

private void doPush(HttpServletRequest request, HttpServletResponse response) {
    // In order to forward the request we need to use a cross-context dispatch.
    //
    // To make this work, crossContext="true" needs to be added to the Context definition
    // in tomcat/conf/context.xml file:
    //
    // <Context sessionCookiePathUsesTrailingSlash="false" crossContext="true">
    //     ...
    // </Context>
    //
    // Get the ServletContext we are currently running in and that of the destination.
    ServletContext myContext = request.getServletContext();
    ServletContext cbContext = myContext.getContext("/backend");

    // Create the forwarding URL based on the project ID in the request.
    final String forwardURL = "/rest/scm/github" + Utils.getProjectID(request);

    // Forward the request.
    try {
        RequestDispatcher dispatcher = cbContext.getRequestDispatcher(forwardURL);
        if (dispatcher != null) {
            dispatcher.forward(request, response);
        } else {
            throw new NullPointerException("No dispatecher found");
        }
    }

    catch (ServletException | IOException ex)
    {
        logger.error("Oops");
    }
}