import nxt.util.CountingInputStream; //导入依赖的package包/类
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

    PeerImpl peer = null;
    JSONStreamAware response;

    try {
        peer = Peers.addPeer(req.getRemoteAddr(), null);
        if (peer == null) {
            return;
        }
        if (peer.isBlacklisted()) {
            return;
        }

        JSONObject request;
        CountingInputStream cis = new CountingInputStream(req.getInputStream());
        try (Reader reader = new BufferedReader(new InputStreamReader(cis, "UTF-8"))) {
            request = (JSONObject) JSONValue.parse(reader);
        }
        if (request == null) {
            return;
        }

        if (peer.getState() == Peer.State.DISCONNECTED) {
            peer.setState(Peer.State.CONNECTED);
        }
        peer.updateDownloadedVolume(cis.getCount());
        if (! peer.analyzeHallmark(peer.getPeerAddress(), (String)request.get("hallmark"))) {
            peer.blacklist();
            return;
        }

        if (request.get("protocol") != null && ((Number)request.get("protocol")).intValue() == 1) {
            PeerRequestHandler peerRequestHandler = peerRequestHandlers.get(request.get("requestType"));
            if (peerRequestHandler != null) {
                response = peerRequestHandler.processRequest(request, peer);
            } else {
                response = UNSUPPORTED_REQUEST_TYPE;
            }
        } else {
            Logger.logDebugMessage("Unsupported protocol " + request.get("protocol"));
            response = UNSUPPORTED_PROTOCOL;
        }

    } catch (RuntimeException e) {
        Logger.logDebugMessage("Error processing POST request", e);
        JSONObject json = new JSONObject();
        json.put("error", e.toString());
        response = json;
    }

    resp.setContentType("text/plain; charset=UTF-8");
    CountingOutputStream cos = new CountingOutputStream(resp.getOutputStream());
    try (Writer writer = new BufferedWriter(new OutputStreamWriter(cos, "UTF-8"))) {
        response.writeJSONString(writer);
    }

    if (peer != null) {
        peer.updateUploadedVolume(cos.getCount());
    }
}