ClassCastException with Document, DocumentTraversal

[Jim Henessey]

Hello,

I am getting a ClassCastException with the code listed below.
The problem is with the line: "DocumentTraversal traversal=(DocumentTraversal) doc", where I get a java.lang.ClassCastException error.

A similar problem was brought up at Previous JavaRanch Topic - what am I doing wrong?and answered by someone with considerable authourity - however, as far as
I can tell Document to DocumentTraversal casting is permitted:

XML APIs Quick Reference
(under the DocumentTraversal section)

Also, most of this code (including the casting) is from the relatively authouritative ibm site:
Using a DOM NodeFilter

Code follows below:

 
public class nodefiltertest
{

private static final String FILE_PATH="...(a local path on my machine, omitted for security reasons)...";
private static final String XML_FILE="calendar_data.xml";


public static void main(String[] args)
{

Document doc=null;

File docFile=new File(FILE_PATH+File.separator+XML_FILE);

try
{
DocumentBuilderFactory dbf=DocumentBuilderFactory.newInstance();
dbf.setValidating(false);
DocumentBuilder db=dbf.newDocumentBuilder();

doc=db.parse(docFile);
}
catch (Exception e)
{
System.out.println("Problem parsing the file.");
}

Node root=doc.getDocumentElement();

int whatToShow=NodeFilter.SHOW_ALL;
NodeFilter nodeFilter=new MonthFilter();

boolean expandReferences=false;

DocumentTraversal traversal=(DocumentTraversal) doc;

TreeWalker walker=
traversal.createTreeWalker(root,whatToShow,nodeFilter,expandReferences);

Node thisNode=null;

thisNode=walker.nextNode();
while (thisNode!=null)
{

Element thisElement=(Element) thisNode;
NamedNodeMap attributes=thisElement.getAttributes();

for(int i=0;i<attributes.getLength();i++)
System.out.println("month: "+attributes.item(i).getNodeValue());

}



}

}

Edit Comment: Added [ code ] [ / code ] tags, without the space.
[ November 02, 2004: Message edited by: Madhav Lakkapragada ]

[Madhav Lakkapragada]

psssstttt......you left out a key peice of info in that link that you
posted. From the DocumentTraversal section of the XML API link that you
posted -

In implementations that support the traversal API (which can be
determined by invoking the hasFeature("Traversal", "2.0" ) method in the
Document or DOMImplementation classes) all objects that implement
Document also implement DocumentTraversal. That is, to create a
DocumentTraversal object, just cast a Document to DocumentTraversal.

So, I would change the code and invoke the hasFrature("Traversal", "2.0")
API and then see what type of results you get.

Please do let us know what you find.
Thanks.

- m

[Jim Henessey]

Originally posted by Madhav Lakkapragada:
psssstttt......you left out a key peice of info in that link that you
posted. From the DocumentTraversal section of the XML API link that you
posted -



So, I would change the code and invoke the hasFrature("Traversal", "2.0")
API and then see what type of results you get.

Please do let us know what you find.
Thanks.

- m

Oh wow - thanks for catching that. That is the source of the problem - when I do a test, I get back that the feature doesn't exist. I'll look for options around this.

Thanks again for your help.

[Madhav Lakkapragada]

Just a hunch. Glad I could help.
Do keep posting.

- m