code: public ReadDocumentResponse readDocument(String documentId) {
          ReadDocumentRequest request = new ReadDocumentRequest();
          request.setDocumentId(documentId);
          return this.readDocument(request);
      }
docs: read a Document, get document reader infomation.
  
  @param documentId  The document id.
  
  @return A ReadDocumentResponse object containing the information returned by Document.