Io exception - cannot close same stream twice

Question

Hi.
Hoping someone can help with this problem. I have a JSP page which is receiving an XML request. Currently I pass the InputStream onto another class (whose source I do not have access to and cannot modify) and this parses the stream and creates a document (and I believe in doing so this closes the stream...is that correct?).
Problem is that now I have to change this JSP page because I need to determine the value of a tag within the XML request before I decide whether to call this class or not. I thought I'd create parse the stream into a document and then reference the node that way. I was able to do this and read the value of that node, but then when I called the class it threw the exception.
So basically I need another way to read the tag from the XML request without closing the stream down. I read some other posts that talked about creating a StringReader and using that, but wouldn't that close the input stream? I also read about using the mark() and reset() methods, but markSupported() returns "false" so I don't think I can use those.
Any ideas will be much appreciated.

Answer 1

Ok, I've tried implemented the solution you suggested but have one problem. I cannot determine the length of the request so I don't know what length to initialise the byte array with. I thought I could use the available() method but this always returns 0. Here is my code (the request is a ServletRequest)...
ServletInputStream sis = request.getInputStream();
int numOfBytes = sis.available();
System.out.println( sis.available() ); //debug
byte b[] = new byte[numOfBytes];
String resultVal = "";
sis.read( b );
ByteArrayInputStream bais = new ByteArrayInputStream( b );
bais.mark( numOfBytes );
// Check whether it is good or bad result
DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance();
DocumentBuilder db=dbf.newDocumentBuilder();
Document doc=db.parse(bais);
NodeList resultNode = doc.getElementsByTagName("result");
resultVal = resultNode.item(0).getFirstChild().getNodeValue();
// Test whether stream can be re-used
bais.reset();
DocumentBuilderFactory dbf2=DocumentBuilderFactory.newInstance();
DocumentBuilder db2=dbf2.newDocumentBuilder();
Document doc2=db2.parse(bais);
if( resultVal.equalsIgnoreCase( "success" ) )
System.out.println( "success!");
else
System.out.println( "not success!");
//more code to call other class with inputstream which parses it into a document
Is there another way I can create the ByteArrayStream? or determine the length of the request?