String xslt = "...."; //корректная таблица преобразования
TransformerFactory factory = TransformerFactory.newInstance();
StreamSource xslStream = new StreamSource(xslt);
Transformer transformer = factory.newTransformer(xslStream); //<-вылетает ошибка 
...

StreamSource xslStream = new StreamSource(xslt);

		private File DoXsltTransform(String data, String xslt, String ext) {
		File resfile = null;
		String outStr = ""; 
	
		xslt = xslt.trim().replaceFirst("^([\\W]+)<", "<");
		
		TransformerFactory factory = TransformerFactory.newInstance();
		try {
			StreamSource in = new StreamSource(data);
		  StreamResult out = new StreamResult(outStr);
		  
		  StreamSource xslStream = new StreamSource(xslt);
		  Transformer transformer = factory.newTransformer(xslStream);
	
		  transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
		  
		  transformer.transform(in, out);
	  	if (outStr.isEmpty() == false) outStr.replace("UTF-16", "UTF-8");
		  resfile = TempFileManager.createTempFile("res", "." + ext);
		  
		  BufferedWriter outF = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(resfile.getPath()), "UTF-8"));
      outF.write(outStr);
      outF.close();

			return resfile;
		} catch (Exception e) {
			System.out.println("Ошибка DoXsltTransform: " + e.getLocalizedMessage());
			resfile.delete();
			return null;
		}
	}

StreamSource xslStream = new StreamSource(xslt);

StreamSource in = new StreamSource(data);
StreamResult out = new StreamResult(outStr);