hi Kris,
I think Xalan does the right thing evaluating

nodes = XPathAPI.selectNodeList(node, "/@name");

starting from the document root. The real problem is not being able to make *relative* XPath queries (without the starting slash). This seems to be a major flaw in the JSTL spec.

Since node variables set with x:set (obviously) work, I looked at the Jakarta impl sources to discover how x:set does the job. Basically it's a big *hack*:

- x:set evaluates the XPath expression with Xalan the wraps the Nodelist result into a org.apache.taglibs.standard.tag.common.xml.JSTLNodeList class.

- when x:out evaluates the XPath expression it checks for the $variable type:
- if it is a JSTLNodeList containing 1 element of type org.w3c.dom.Node, it creates a new Document, imports the Node and then (here comes the hack) it prepends "/*" to the user specified XPath:

xpath="/*" + xpath;
(org.apache.taglibs.standard.tag.common.xml.XPathUtil line 683)

- if the $variable is a org.w3.dom.Node it is used as it is as the XPath Context as expected.

why this different treatment? obviously because of the Xalan behaviour that Kris explained. I think the same hack should be applied to Node variables so they work just like the impl-specific JSTLNodeList.

Any ideas? Any chance to let the developers know? They don't seem to be on this list at all...


Kris Schneider wrote:
It seems like an issue with Xalan's XPath implementation. The Standard 1.1
taglib uses Xalan while Standard 1.0 uses Jaxen/SAXPath. Here's an example app
that mimics what it sounds like Flavio is trying to do:

import java.io.*;
import javax.xml.parsers.*;
import org.apache.xpath.*;
import org.w3c.dom.*;
import org.xml.sax.*;

public class XPathNode {

    private static final String XML =
        "<root name=\"root\"><child name=\"child\"><grandchild

    public static void main(String[] args) throws Exception {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        DocumentBuilder db = dbf.newDocumentBuilder();
        Document doc = db.parse(new InputSource(new StringReader(XML)));
        Element root = doc.getDocumentElement();
        Node node = root.getFirstChild();
        NodeList nodes = null;

        nodes = XPathAPI.selectNodeList(doc, "/root/child/@name");

        nodes = XPathAPI.selectNodeList(node, "/@name");

        nodes = XPathAPI.selectNodeList(node, "./@name");

    public static void printNodes(NodeList nodes) {
        for (int i = 0, n = nodes.getLength(); i < n; i++) {
            Node node = nodes.item(i);
            System.out.println("\t" + node);

Which results in:


Notice that for the XPath evaluation to work with "node", I had to prepend "."
to the expression. I'm not sure if it's possible to construct something similar
with the "select" attribute of JSTL's x tags...

Quoting "Johnson, Chris" <[EMAIL PROTECTED]>:

I see.  I ran across a similar problem with JDOM Xpath, although they
solved it in a newer version, but totally screwed up the API and some
other stuff, so it killed the fix for me.

I had performance problems with the xml jstl tags (forEach), so I've
since moved on to using xslt.  They're clearly not in a big hurry to fix
these (what we would consider big) problems.


-----Original Message-----
From: Flavio Tordini [mailto:[EMAIL PROTECTED] Sent: Wednesday, September 08, 2004 10:36 AM
To: Tag Libraries Users List
Subject: Re: using Node variables with JSTL XML tags

hi chris,
thank you for your answer. The problem is i'm actually passing a *Node* to the tag, not a Document. So I'd like to evaluate the XPath starting from that Node, not from the root of the Document the Node belongs to.

I also tried:
<x:forEach select="$node">
  <x:out select="@name"/>

and it works. But it's kind of a hack. I'm not searching for a workaround, I need a clean solution since i'm working on a project that aims to simplify JSP development with the aid of the JSTL + plus a custom Servlet, and I cannot expect people to use this "forEach" hack.


Johnson, Chris wrote:

It seems that what 1.1 is doing is more correct.

How do you expect jstl to find your sub node without telling it how to

get there? That's how it works in directories on a computer (unix or pc). The only way that I know of to go to a subnode without providing

the full path is by using the // operator, like: select="$doc//subnode". Otherwise, the only way (that I know of) to "cd" to a subnode, and therefore not have to give the full path is by using x:forEach.


-----Original Message-----
From: Flavio Tordini [mailto:[EMAIL PROTECTED]
Sent: Wednesday, September 08, 2004 9:37 AM
To: Tag Libraries Users List
Subject: Re: using Node variables with JSTL XML tags

hi all, In the list archive, I found that the same question has been asked in June e never answered:

http://www.mail-archive.com/[EMAIL PROTECTED]/msg07315.h

should I post to the dev mailing list?
should I report a bug?

please someone answer!


Flavio Tordini wrote:

hi all,
I'm experimenting with the JSTL XML tags. I have a org.w3c.dom.Node variable and I'm trying to use the JSTL with it. Something like:

<x:out select="$node/@name"/>

The odd thing is that the XPath expression is evaluated relative the document root, not to the specified node. The following works:

<x:out select="$node/full/path/to/node/@name"/>

I cannot find an explanation in the JSTL 1.1 spec. The only thing I found is in section 11.1.3:

"An XPath expression must also treat variables that resolve to implementations of standard DOM interfaces as representing nodes of


type bound to that interface by the DOM specification."

Is this behaviour by design? Is it compliant with the spec?

Thank you in advance,

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