XALAN: Text node of value 'null' - Is this illegal or does XSLTC have an issue here?

[huizhe wang]

Looks like a null check-in is desirable. If the intention is to add a 
text node, which I assume was his intention, he wouldn't want a null 
node. If the intention is to create an empty element, then he didn't 
need the line that added the null text node.

As far as DOM goes, it would have been better if it was clearer on how 
null be handled (a DOMException probably). But for a 10+ yr old API, the 
case is not enough to call for a change of the behavior.

Thanks,
Joe

On 11/7/2016 8:09 AM, Langer, Christoph wrote:
>
> Hi Xalan experts,
>
> I’ve recently handled a customer issue about Text Nodes of value 
> ‘null’ inside a DOM, causing an exception during XALAN XSLT 
> transformation. The repro case is quite simple. Consider the following 
> small Java sample [1] which creates a DOM from a very basic XML, 
> inserts a text node with value null into the DOM and then runs an 
> identity transformation on it. Without inserting the null Text node, 
> it would run without issues. However, the 
> com.sun.org.apache.xml.internal.serializer.ToUnknownStream class 
> stumbles over the null value and the transformation throws an NPE [2]. 
> I believe this could be easily fixed by adding a null check in the 
> serializer and handling null like “”. However, would you agree that it 
> is a real issue worth fixing or should one rather stress the point 
> that Text Nodes of null are illegal? (Is that true, anyway? Didn’t 
> find any specification about that…) Please let me know your opinion – 
> and if you agree I would work on a fix.
>
> Thanks in advance for comments
>
> Christoph
>
> [1] Sample code:
>
> import java.io.ByteArrayInputStream;
>
> import java.io.ByteArrayOutputStream;
>
> import java.io.IOException;
>
> import javax.xml.parsers.DocumentBuilder;
>
> import javax.xml.parsers.DocumentBuilderFactory;
>
> import javax.xml.parsers.ParserConfigurationException;
>
> import javax.xml.transform.TransformerException;
>
> import javax.xml.transform.TransformerFactory;
>
> import javax.xml.transform.dom.DOMSource;
>
> import javax.xml.transform.stream.StreamResult;
>
> import org.w3c.dom.Document;
>
> import org.w3c.dom.Element;
>
> import org.xml.sax.SAXException;
>
> public class TestTransformWithNullText {
>
>                 public static void main(String[] args) throws 
> ParserConfigurationException, SAXException, IOException, 
> TransformerException {
>
> // create a small DOM
>
> DocumentBuilder db = 
> DocumentBuilderFactory.newInstance().newDocumentBuilder();
>
> Document doc = db.parse(new ByteArrayInputStream("<?xml 
> version=\"1.0\"?><DOCROOT/>".getBytes()));
>
> // insert a bad element
>
> Element e = doc.createElement("ERROR");
>
> e.appendChild(doc.createTextNode(null));
>
> doc.getDocumentElement().appendChild(e);
>
> // transform
>
> ByteArrayOutputStream bos = new ByteArrayOutputStream();
>
> TransformerFactory.newInstance().newTransformer().transform(
>
> new DOMSource(doc.getDocumentElement()), new StreamResult(bos));
>
> System.out.println(bos);
>
>                 }
>
> }
>
> [2] Exception encountered:
>
> Exception in thread "main" javax.xml.transform.TransformerException: 
> java.lang.NullPointerException
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(java.xml at 9.0.0.1-internal/TransformerImpl.java:789)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(java.xml at 9.0.0.1-internal/TransformerImpl.java:376)
>
>         at 
> com.sap.cl.xml.test.transform.TestTransformWithNullText.main(TestTransformWithNullText.java:33)
>
> Caused by: java.lang.NullPointerException
>
>         at 
> com.sun.org.apache.xml.internal.serializer.ToUnknownStream.characters(java.xml at 9.0.0.1-internal/ToUnknownStream.java:342)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:244)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:230)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:230)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:94)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(java.xml at 9.0.0.1-internal/TransformerImpl.java:718)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(java.xml at 9.0.0.1-internal/TransformerImpl.java:780)
>
>         ... 2 more
>
> ---------
>
> java.lang.NullPointerException
>
>         at 
> com.sun.org.apache.xml.internal.serializer.ToUnknownStream.characters(java.xml at 9.0.0.1-internal/ToUnknownStream.java:342)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:244)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:230)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:230)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.DOM2TO.parse(java.xml at 9.0.0.1-internal/DOM2TO.java:94)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transformIdentity(java.xml at 9.0.0.1-internal/TransformerImpl.java:718)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(java.xml at 9.0.0.1-internal/TransformerImpl.java:780)
>
>         at 
> com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(java.xml at 9.0.0.1-internal/TransformerImpl.java:376)
>
> at 
> com.sap.cl.xml.test.transform.TestTransformWithNullText.main(TestTransformWithNullText.java:33)
>