проблема со StringReader

     public String transform(String what, String sxml) throws Exception {
        String resultHtml = what + "<br />" + sxml + "<br />" + "empty!!!<br />";
        try {
            XSLTransformer transformer = new XSLTransformer(this.getXslFilePath(what));
            SAXBuilder saxBuilder = new SAXBuilder();
 
            StringReader xmlStringReader = new StringReader(sxml);      //здесь образуется проблема
   
            Document xmlDocument = saxBuilder.build(xmlStringReader);       //здесь вылетает эксепшн
 
            Document transformedDocument = transformer.transform(xmlDocument);
            StringWriter htmlStringWriter = new StringWriter();
            new XMLOutputter().output(transformedDocument, htmlStringWriter);
            resultHtml = htmlStringWriter.getBuffer().toString();
        } catch (Exception ex) {
            throw new Exception(resultHtml += ex.getMessage() + "<br />Exception: " + ex.getLocalizedMessage());
        }
        return resultHtml;
    }

public class StringReader extends Reader {
 
    private String str;
    private int length;
    private int next = 0;
    private int mark = 0;
 
 
    public StringReader(String s) {
        this.str = s;
        this.length = s.length();
    }

StringReader xmlStringReader = new StringReader(sxml);