XML Validation From Schema In Servlet Filter

[MJ]

I am attempting to write a ServletFilter in Java/J2EE that checks if
the incoming data is valid according to a schema. If errors occur, I
want to return the error list and not proceed down the chain. If no
errors, the next in the servlet chain should receive the original XML.

The data in the input stream has already been consumed by the XML
parser.
What is the easiest way to validate the XML and keep the source xml
available for the next link in the chain?

something like...

public void doFilter(Servle tRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletExceptio n {
// we want to stream the input stream thru a SAX validation and
check for errors
ValidationHandl er handler = new ValidationHandl er();
try {
XMLReader reader =
XMLReaderFactor y.createXMLRead er("org.apache. xerces.parsers. SAXParser");
reader.setFeatu re("http://xml.org/sax/features/validation",
true);
reader.setFeatu re("http://apache.org/xml/features/validation/schema",
true);
reader.setPrope rty("http://apache.org/xml/properties/schema/external-schemaLocation" ,
"test" + test.xsd);
reader.setError Handler(handler );
reader.setConte ntHandler(handl er);

InputStream inStream = request.getInpu tStream();
InputSource inSource = new InputSource(inS tream);
reader.parse(in Source);

if (handler.hasErr ors()) {
//write back errors in the response
}
else // parsed successfully now process
chain.doFilter( request, response);

}
catch (SAXException e) {
//write back errors in the response
}
}