transforming dom with a CDATA section set to null

[Tim Cronin <ti...@13-colonies.com>]

I'm using Xalan 2.4.1 and xerces 2.2.1.

(I posted to xerces as well...)

I was building a Document and a passed a null to the call createCDATASection
(this did not fail which surprised me..)


when I tried to transform (basically creating a string of the dom) 

  public static String toString(Node node)
  {  
    StringWriter sw = new StringWriter();

    try
    {
      Transformer serializer =
TransformerFactory.newInstance().newTransformer();
      serializer.transform(new DOMSource(node), new StreamResult(sw));
    }
    catch (TransformerException e)
    {
      DOMException de = new DOMException(DOMException.SYNTAX_ERR, "failed to
translate DOM");
      de.initCause(e);
      throw de;
    }
    return sw.toString();
  }


it I got the following

java.lang.NullPointerException
        at
org.apache.xml.utils.TreeWalker.dispatachChars(TreeWalker.java:292)
        at org.apache.xml.utils.TreeWalker.startNode(TreeWalker.java:412)
        at org.apache.xml.utils.TreeWalker.traverse(TreeWalker.java:191)
        at
org.apache.xalan.transformer.TransformerIdentityImpl.transform(TransformerId
entityImpl.java:325)

it also failed for xslt transformation

java.lang.NullPointerException
        at
org.apache.xalan.xsltc.runtime.output.StreamXMLOutput.characters(StreamXMLOu
tput.java:199)
        at
org.apache.xalan.xsltc.runtime.output.StreamUnknownOutput.characters(StreamU
nknownOutput.java:177)
        at org.apache.xalan.xsltc.trax.DOM2TO.parse(DOM2TO.java:144)
        at org.apache.xalan.xsltc.trax.DOM2TO.parse(DOM2TO.java:209)
        at org.apache.xalan.xsltc.trax.DOM2TO.parse(DOM2TO.java:209)
        at org.apache.xalan.xsltc.trax.DOM2TO.parse(DOM2TO.java:115)
        at
org.apache.xalan.xsltc.trax.TransformerImpl.transformIdentity(TransformerImp
l.java:612)
        at
org.apache.xalan.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:6
32)


I would expect to get a NullPointerException when I created the
CDATASection.

Re: transforming dom with a CDATA section set to null

[Joseph Kesselman <ke...@us.ibm.com>]

I'm afraid this is a clear case of "If it hurts when you do that, and you 
know you shouldn't do that, stop doing that."

Passing nulls into the DOM API where they aren't expected may trigger 
error responses at the time you set those values or at the time you read 
them or both. This was deliberately left for DOM implementations to decide 
since it's a performance-versus-robustness issue. Obviously, if the DOM 
decided not to spend time protecting itself and instead fails when 
accessed, a bad DOM may disrupt the transformation.

We might be able to configure Xalan to check for this. But again, that 
means spending cycles testing for something that you shouldn't have 
created in the first place.


To resolve this: Determine whether the DOM officially considers null a 
legitimate value when set, and if so what it returns when retrieved. If 
the answer to the first is yes and the answer to the second is null, Xalan 
will have to tolerate the null. If the answer to the first is yes and the 
answer to the second is empty-string, Xerces has a problem. If the answer 
to the first is null, your application code has a problem.

______________________________________
Joe Kesselman  / IBM Research