code: public ReadDocumentResponse readDocument(ReadDocumentRequest request) {
          checkNotNull(request, "request should not be null.");
          checkNotNull(request.getDocumentId(), "documentId should not be null.");
          InternalRequest internalRequest = this.createRequest(
                  HttpMethodName.GET, request, DOC, request.getDocumentId());
          internalRequest.addParameter("read", null);
          ReadDocumentResponse response;
          try {
              response = this.invokeHttpClient(internalRequest, ReadDocumentResponse.class);
          } finally {
              try {
                  internalRequest.getContent().close();
              } catch (Exception e) {
                  // ignore exception
              }
          }
  
          return response;
      }
docs: read a Document, get document reader infomation.
  
  @param request  The request object containing a documentId.
  
  @return A ReadDocumentResponse object containing the information returned by Document.