private String getDocumentString(Document doc) {
        StringWriter stringWriter = new StringWriter();
        OutputFormat outputFormat = OutputFormat.createPrettyPrint();
        outputFormat.setIndentSize(4);
        XMLWriter serializer = new XMLWriter(stringWriter, outputFormat);
        try {
            serializer.write(doc);
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
        return stringWriter.toString();
    }