public Object clone() 
{
        XPathExtractor cloned = (XPathExtractor) super.clone();
        return cloned;
}

 public String getDefaultValue() 
{
        return getPropertyAsString(DEFAULT);
}

 public String getRefName() 
{
        return getPropertyAsString(REFNAME);
}

 public String getXPathQuery() 
{
        return getPropertyAsString(XPATH_QUERY);
}

 public boolean isQuiet() 
{
        return getPropertyAsBoolean(QUIET, true);
}

 public boolean isTolerant() 
{
        return getPropertyAsBoolean(TOLERANT);
}

 public  void process() 
{
        JMeterContext context = getThreadContext();
        JMeterVariables vars = context.getVariables();
        String refName = getRefName();
        vars.put(refName, getDefaultValue());
        vars.put(concat(refName,MATCH_NR), "0"); // In case parse fails // $NON-NLS-1$
        vars.remove(concat(refName,"1")); // In case parse fails // $NON-NLS-1$
        final SampleResult previousResult = context.getPreviousResult();
        try{
            Document d = parseResponse(previousResult);
            getValuesForXPath(d,getXPathQuery(),vars, refName);
        }catch(IOException e){// Should not happen
            final String errorMessage = "error on ("+getXPathQuery()+")";
            log.error(errorMessage,e);
            throw new JMeterError(errorMessage,e);
        } catch (ParserConfigurationException e) {// Should not happen
            final String errrorMessage = "error on ("+getXPathQuery()+")";
            log.error(errrorMessage,e);
            throw new JMeterError(errrorMessage,e);
        } catch (SAXException e) {// Can happen for bad input document
            log.warn("error on ("+getXPathQuery()+")"+e.getLocalizedMessage());
        } catch (TransformerException e) {// Can happen for incorrect XPath expression
            log.warn("error on ("+getXPathQuery()+")"+e.getLocalizedMessage());
        } catch (TidyException e) {
            AssertionResult ass = new AssertionResult("TidyException"); // $NON-NLS-1$
            ass.setFailure(true);
            ass.setFailureMessage(e.getMessage());
            previousResult.addAssertionResult(ass);
            previousResult.setSuccessful(false);
        }
}

Do the job - extract value from (X)HTML response using XPath Query. Return value as variable defined by REFNAME. Returns DEFAULT value if not found.

 public boolean reportErrors() 
{
        return getPropertyAsBoolean(REPORT_ERRORS, false);
}

 public  void setDefaultValue(String val) 
{
        setProperty(DEFAULT, val);
}

 public  void setNameSpace(boolean val) 
{
        setProperty(new BooleanProperty(NAMESPACE, val));
}

 public  void setQuiet(boolean val) 
{
        setProperty(QUIET, val, true);
}

 public  void setRefName(String refName) 
{
        setProperty(REFNAME, refName);
}

 public  void setReportErrors(boolean val) 
{
            setProperty(REPORT_ERRORS, val, false);
}

 public  void setShowWarnings(boolean val) 
{
        setProperty(SHOW_WARNINGS, val, false);
}

 public  void setTolerant(boolean val) 
{
        setProperty(new BooleanProperty(TOLERANT, val));
}

 public  void setXPathQuery(String val) 
{
        setProperty(XPATH_QUERY,val);
}

 public boolean showWarnings() 
{
        return getPropertyAsBoolean(SHOW_WARNINGS, false);
}

 public boolean useNameSpace() 
{
        return getPropertyAsBoolean(NAMESPACE);
}