public static class ThreadTraceListener implements ThreadListener {
    @Override
    public void onThreadBegin(HttpServletRequest request) {
      String traceToken = ThreadLocalUtil.getTranVar(TRACE_ID);
      String fromServer = ThreadLocalUtil.getTranVar(FROM_SERVER);
      int deep;
      String traceId;
      if (StringUtils.isBlank(traceToken)) {
        traceId = IDGenerator.generateID();
        deep = 0;
        traceToken = StringHelper.join(traceId, ":0");
      } else {
        int index = traceToken.lastIndexOf(':');
        traceId = traceToken.substring(0, index);
        deep = Integer.valueOf(traceToken.substring(index + 1));
      }
      ThreadLocalUtil.setLocalVar(TRACE_ID, traceId);
      ThreadLocalUtil.setLocalVar(TRACE_DEEP, deep);
      ThreadLocalUtil.setTranVar(TRACE_ID, StringHelper.join(traceId, ":", deep + 1));
      ThreadLocalUtil.setLocalVar(FROM_SERVER, fromServer);
      ThreadLocalUtil.setTranVar(FROM_SERVER, getCurrentServer());
      MDC.put(TRACE_ID, StringHelper.join(traceToken, ":", fromServer));
    }

    @Override
    public void onThreadEnd(HttpServletRequest request) {
      MDC.remove(TRACE_ID);
    }
  }

protected void doFilterInternal(HttpServletRequest request,
      HttpServletResponse response,
      FilterChain chain) throws ServletException, IOException {
    long startTime = System.currentTimeMillis();
    // 從Header中裝載傳遞過來的變量
    Map<String, Object> tranVar = new HashMap<String, Object>();
    Enumeration<String> headers = request.getHeaderNames();
    while (headers.hasMoreElements()) {
      String key = headers.nextElement();
      if (!StringUtils.isEmpty(key)
          && key.startsWith(ThreadLocalUtil.TRAN_PREFIX)) {
        tranVar.put(key.substring(ThreadLocalUtil.TRAN_PREFIX.length()),
            request.getHeader(key));
      }
    }
    ThreadLocalHolder.begin(tranVar, request);
    try {
      if (isGateway) {
        response.addHeader("X-TRACE-ID", TraceUtil.getTraceId());
      }
      // 檢查RPC調(diào)用深度
      checkRpcDeep(request, response);
      // 業(yè)務(wù)處理
      chain.doFilter(request, response);
      // 記錄RPC調(diào)用次數(shù)
      logRpcCount(request, response);
    } catch (Throwable ex) {
      // 錯誤處理
      Response<?> result = ExceptionUtil.toResponse(ex);
      Determine determine = ExceptionUtil.determineType(ex);
      ExceptionUtil.doLog(result, determine.getStatus(), ex);
      response.setStatus(determine.getStatus().value());
      response.setCharacterEncoding("UTF-8");
      response.setContentType(MediaType.APPLICATION_JSON_UTF8_VALUE);
      response.getWriter().write(JsonUtil.toJsonString(result));
    } finally {
      try {
        doMonitor(request, response, startTime);
        if (TraceUtil.isTraceLoggerOn()) {
          log.warn(StringHelper.join(
              "TRACE-HTTP-", request.getMethod(),
              " URI:", request.getRequestURI(),
              ", dt:", System.currentTimeMillis() - startTime,
              ", rpc:", TraceUtil.getRpcCount(),
              ", status:", response.getStatus()));
        } else if (log.isTraceEnabled()) {
          log.trace(StringHelper.join(request.getMethod(),
              " URI:", request.getRequestURI(),
              ", dt:", System.currentTimeMillis() - startTime,
              ", rpc:", TraceUtil.getRpcCount(),
              ", status:", response.getStatus()));
        }
      } finally {
        ThreadLocalHolder.end(request);
      }
    }
}