Snippet from Google JS Test Driver. Forwards requests to another server and feeds the responses back to the client. git clone https://code.google.com/p/js-test-driver/

GatewayRequestHandler.java

  @Override
  public void handleIt() throws IOException {
    final HttpMethodBase method = getMethod(request);
    addRequestHeaders(method, request);
    method.setQueryString(request.getQueryString());
    spoofHostHeader(method);
    try {
      final int statusCode = client.executeMethod(method);
      response.setStatus(statusCode);
      addResponseHeaders(method, response);
      if (isRedirect(statusCode)) {
        spoofLocationHeader(request, (Response) response);
      }   
      if (isStatusCodeSuppressed(request)) {
        response.setStatus(HttpServletResponse.SC_OK);
        response.addIntHeader(X_SUPPRESSED_STATUS_CODE, statusCode);
        response.addHeader(X_SUPPRESSED_REASON_PHRASE, method.getStatusText());
      }   
      // TODO(rdionne): Substitute the JsTD server address for the destination address in any redirects.
      Streams.copy(method.getResponseBodyAsStream(), response.getOutputStream());
    } catch (IOException e) {
      response.setStatus(HttpServletResponse.SC_BAD_GATEWAY);
      e.printStackTrace(response.getWriter());
    } finally {
      method.releaseConnection();
    }   
  }