code: @CheckForSigned
    public static long getContentLength (@Nonnull final HttpServletRequest aHttpRequest)
    {
      ValueEnforcer.notNull (aHttpRequest, "HttpRequest");
  
      if (false)
      {
        // Missing support > 2GB!!!
        return aHttpRequest.getContentLength ();
      }
  
      final String sContentLength = aHttpRequest.getHeader (CHttpHeader.CONTENT_LENGTH);
      return StringParser.parseLong (sContentLength, -1L);
    }
docs: Get the content length of the passed request. This is not done using
  <code>request.getContentLength()</code> but instead parsing the HTTP header
  field {@link CHttpHeader#CONTENT_LENGTH} manually!
  
  @param aHttpRequest
  Source HTTP request. May not be <code>null</code>.
  @return -1 if no or an invalid content length is set in the header