/**
   * Creates new HTTP requests handler.
   *
   * @param hnd Handler.
   * @param authChecker Authentication checking closure.
   * @param log Logger.
   */
  GridJettyRestHandler(
      GridRestProtocolHandler hnd, GridClosure<String, Boolean> authChecker, GridLogger log) {
    assert hnd != null;
    assert log != null;

    this.hnd = hnd;
    this.log = log;
    this.authChecker = authChecker;

    // Init default page and favicon.
    try {
      initDefaultPage();

      if (log.isDebugEnabled()) log.debug("Initialized default page.");
    } catch (IOException e) {
      U.warn(log, "Failed to initialize default page: " + e.getMessage());
    }

    try {
      initFavicon();

      if (log.isDebugEnabled())
        log.debug(
            favicon != null ? "Initialized favicon, size: " + favicon.length : "Favicon is null.");
    } catch (IOException e) {
      U.warn(log, "Failed to initialize favicon: " + e.getMessage());
    }
  }
  /** {@inheritDoc} */
  @Override
  public void handle(String target, Request req, HttpServletRequest srvReq, HttpServletResponse res)
      throws IOException, ServletException {
    if (log.isDebugEnabled())
      log.debug("Handling request [target=" + target + ", req=" + req + ", srvReq=" + srvReq + ']');

    if (target.startsWith("/gridgain")) {
      processRequest(target, srvReq, res);

      req.setHandled(true);
    } else if (target.startsWith("/favicon.ico")) {
      if (favicon == null) {
        res.setStatus(HttpServletResponse.SC_NOT_FOUND);

        req.setHandled(true);

        return;
      }

      res.setStatus(HttpServletResponse.SC_OK);

      res.setContentType("image/x-icon");

      res.getOutputStream().write(favicon);
      res.getOutputStream().flush();

      req.setHandled(true);
    } else {
      if (dfltPage == null) {
        res.setStatus(HttpServletResponse.SC_NOT_FOUND);

        req.setHandled(true);

        return;
      }

      res.setStatus(HttpServletResponse.SC_OK);

      res.setContentType("text/html");

      res.getWriter().write(dfltPage);
      res.getWriter().flush();

      req.setHandled(true);
    }
  }
  /**
   * Process HTTP request.
   *
   * @param act Action.
   * @param req Http request.
   * @param res Http response.
   */
  private void processRequest(String act, HttpServletRequest req, HttpServletResponse res) {
    res.setContentType("application/json");
    res.setCharacterEncoding("UTF-8");

    GridRestCommand cmd = command(req);

    if (cmd == null) {
      res.setStatus(HttpServletResponse.SC_BAD_REQUEST);

      return;
    }

    if (!authChecker.apply(req.getHeader("X-Signature"))) {
      res.setStatus(HttpServletResponse.SC_UNAUTHORIZED);

      return;
    }

    GridRestResponse cmdRes;

    Map<String, Object> params = parameters(req);

    try {
      GridRestRequest cmdReq = createRequest(cmd, params, req);

      if (log.isDebugEnabled()) log.debug("Initialized command request: " + cmdReq);

      cmdRes = hnd.handle(cmdReq);

      if (cmdRes == null)
        throw new IllegalStateException("Received null result from handler: " + hnd);

      byte[] sesTok = cmdRes.sessionTokenBytes();

      if (sesTok != null) cmdRes.setSessionToken(U.byteArray2HexString(sesTok));

      res.setStatus(HttpServletResponse.SC_OK);
    } catch (Exception e) {
      res.setStatus(HttpServletResponse.SC_OK);

      U.error(log, "Failed to process HTTP request [action=" + act + ", req=" + req + ']', e);

      cmdRes = new GridRestResponse(STATUS_FAILED, e.getMessage());
    } catch (Throwable e) {
      U.error(log, "Failed to process HTTP request [action=" + act + ", req=" + req + ']', e);

      throw e;
    }

    JsonConfig cfg = new GridJettyJsonConfig();

    // Workaround for not needed transformation of string into JSON object.
    if (cmdRes.getResponse() instanceof String)
      cfg.registerJsonValueProcessor(cmdRes.getClass(), "response", SKIP_STR_VAL_PROC);

    if (cmdRes.getResponse() instanceof GridClientTaskResultBean
        && ((GridClientTaskResultBean) cmdRes.getResponse()).getResult() instanceof String)
      cfg.registerJsonValueProcessor(cmdRes.getResponse().getClass(), "result", SKIP_STR_VAL_PROC);

    JSON json;

    try {
      json = JSONSerializer.toJSON(cmdRes, cfg);
    } catch (JSONException e) {
      U.error(log, "Failed to convert response to JSON: " + cmdRes, e);

      json = JSONSerializer.toJSON(new GridRestResponse(STATUS_FAILED, e.getMessage()), cfg);
    }

    try {
      if (log.isDebugEnabled())
        log.debug("Parsed command response into JSON object: " + json.toString(2));

      res.getWriter().write(json.toString());

      if (log.isDebugEnabled())
        log.debug(
            "Processed HTTP request [action=" + act + ", jsonRes=" + cmdRes + ", req=" + req + ']');
    } catch (IOException e) {
      U.error(log, "Failed to send HTTP response: " + json.toString(2), e);
    }
  }