public void handle()

in server/src/main/java/org/apache/calcite/avatica/server/AvaticaProtobufHandler.java [90:155]
56 lines of code
9 McCabe index (conditional complexity)

  public void handle(String target, Request baseRequest,
      HttpServletRequest request, HttpServletResponse response)
      throws IOException, ServletException {
    try (Context ctx = this.requestTimer.start()) {
      if (!request.getMethod().equals("POST")) {
        response.setStatus(HttpServletResponse.SC_BAD_REQUEST);
        response.getOutputStream().write(
            "This server expects only POST calls.".getBytes(StandardCharsets.UTF_8));
        baseRequest.setHandled(true);
        return;
      }

      // Check if the user is OK to proceed.
      if (!isUserPermitted(serverConfig, baseRequest, request, response)) {
        LOG.debug("HTTP request from {} is unauthenticated and authentication is required",
            request.getRemoteAddr());
        return;
      }

      final byte[] requestBytes;
      // Avoid a new buffer creation for every HTTP request
      final UnsynchronizedBuffer buffer = threadLocalBuffer.get();
      try (ServletInputStream inputStream = request.getInputStream()) {
        requestBytes = AvaticaUtils.readFullyToBytes(inputStream, buffer);
      } finally {
        buffer.reset();
      }

      response.setContentType("application/octet-stream;charset=utf-8");
      response.setStatus(HttpServletResponse.SC_OK);
      HandlerResponse<byte[]> handlerResponse;
      try {
        if (null != serverConfig && serverConfig.supportsImpersonation()) {
          // If we can't extract a user, need to throw 401 in that case.
          String remoteUser = serverConfig.getRemoteUserExtractor().extract(request);
          // Invoke the ProtobufHandler inside as doAs for the remote user.
          // The doAsRemoteUser call may disallow a user, need to throw 403 in that case.
          handlerResponse = serverConfig.doAsRemoteUser(remoteUser,
            request.getRemoteAddr(), new Callable<HandlerResponse<byte[]>>() {
              @Override public HandlerResponse<byte[]> call() {
                return pbHandler.apply(requestBytes);
              }
            });
        } else {
          handlerResponse = pbHandler.apply(requestBytes);
        }
      } catch (RemoteUserExtractionException e) {
        LOG.debug("Failed to extract remote user from request", e);
        handlerResponse = pbHandler.unauthenticatedErrorResponse(e);
      } catch (RemoteUserDisallowedException e) {
        LOG.debug("Remote user is not authorized", e);
        handlerResponse = pbHandler.unauthorizedErrorResponse(e);
      } catch (BadRequestException e) {
        LOG.debug("Bad request exception", e);
        handlerResponse = pbHandler.badRequestErrorResponse(e);
      } catch (Exception e) {
        LOG.debug("Error invoking request from {}", baseRequest.getRemoteAddr(), e);
        // Catch at the highest level of exceptions
        handlerResponse = pbHandler.convertToErrorResponse(e);
      }

      baseRequest.setHandled(true);
      response.setStatus(handlerResponse.getStatusCode());
      response.getOutputStream().write(handlerResponse.getResponse());
    }
  }