Convert XML file to XML String in java

I had to find out a way to read an XML file, and convert it to java String. Below is the code snippet I used.

public String convertXMLFileToString(String fileName)
        {
          try{
            DocumentBuilderFactory documentBuilderFactory = DocumentBuilderFactory.newInstance();
            InputStream inputStream = new FileInputStream(new File(fileName));
            org.w3c.dom.Document doc = documentBuilderFactory.newDocumentBuilder().parse(inputStream);
            StringWriter stw = new StringWriter();
            Transformer serializer = TransformerFactory.newInstance().newTransformer();
            serializer.transform(new DOMSource(doc), new StreamResult(stw));
            return stw.toString();
          }
          catch (Exception e) {
            e.printStackTrace();
          }
            return null;
        }