RE: [Java] NullPointerException with XMLSignature transformations

[Mark.Priest]

Johan,

I am not sure if this information is helpful but I will mention it anyway.  We were 
receiving a null pointer exception in xpath-related code when we were verifying a 
signature.  Our problem turned out to be that our app server was using a different 
version of some Xalan xpath classes. When we moved our xalan impl earlier in the 
classpath the problem went away.  I hope that helps.

-Mark


-----Original Message-----
From: Johan Vanbockryck (jvanbock) [mailto:[EMAIL PROTECTED]
Sent: Friday, March 12, 2004 5:00 AM
To: [EMAIL PROTECTED]
Subject: [Java] NullPointerException with XMLSignature transformations


Hi,

We're experiencing a NullPointerException when we try to sign an XML
document when the transformations are being performed. We've been able
to trace the cause of the problem, and are wondering if this is a bug in
the XML signature code.
What happens is:
We use Axis with HTTP web services. Before the HTTP request is sent, an
XML signature is created on some parts of the SOAP message that is being
sent. We retrieve the XML document from the Axis message context, sign
the XML and reassign the document to Axis. The problem is caused by
XMLUtils class in the 'public static Document getOwnerDocument(Set
xpathNodeSet)' method. In this method an iterator is retrieved from the
Set and the owner of the first element retrieved from this iterator is
returned as owner document. For some reason, there are some attribute
nodes in the document we receive from Axis that have no owner document
(I didn't know this was possible, but Axis appears to be able to do
that). When the first is such an attribute, 'null' will be returned as
owner document and this causes the exception at a later stage in the
code. What we're wondering is if the method as it is now:

public static Document getOwnerDocument(Set xpathNodeSet) {
   NullPointerException npe = null;
   Iterator iterator = xpathNodeSet.iterator();
   while(iterator.hasNext()) {
       Node node = (Node) iterator.next();
       if (node.getNodeType() == Node.DOCUMENT_NODE) {
          return (Document) node;
       } else {
          try {
                 return node.getOwnerDocument();
          } catch (NullPointerException e) {
              npe = e;
          }
       }
   }
   throw new NullPointerException(I18n.translate("endorsed.jdk1.4.0")
                                   + " Original message was \""
                                   + (npe == null ? "" :
npe.getMessage()) + "\"");
}


shouldn't be:

public static Document getOwnerDocument(Set xpathNodeSet) {
   NullPointerException npe = null;
   Iterator iterator = xpathNodeSet.iterator();
   while(iterator.hasNext()) {
       Node node = (Node) iterator.next();
       if (node.getNodeType() == Node.DOCUMENT_NODE) {
          return (Document) node;
       } else {
          try {
                 Document doc;
                 doc = node.getOwnerDocument();
                 if (doc != null)
                return doc;
          } catch (NullPointerException e) {
              npe = e;
          }
       }
   }
   throw new NullPointerException(I18n.translate("endorsed.jdk1.4.0")
                                   + " Original message was \""
                                   + (npe == null ? "" :
npe.getMessage()) + "\"");
}


The usage of the while(iterator.hasNext()) would seem a bit redundant if
it's only the first element is ever checked ...
(as a side note, I'm using a CVS checkout from 2004-02-23)


Regards,

Johan