XSLT FAQs

How do I tell Cocoon to stop adding carriage-returns during XSL transformation?

The short answer is that this is not a Cocoon issue. You need to read up on XSLT usage. Please see other resources for XSLT, specifically, the XSL FAQ and discussion lists.

The long answer is that you need to use the XSLT function normalize-space() whenever you want to rely on the content of an xml element.

For example, if your application is producing some Javascript code in your HTML output, then you might mistakenly try to use the following construct in your XSL stylesheet:

alert('<xsl:value-of select="message"/>');

which will produce:

alert('
messageValue
');

The line-endings in the content of your "message" element will cause javascript errors. Instead, do this:

alert('<xsl:value-of select="normalize-space(message)"/>');

Note that there are many more issues about whitespace handling. Please refer to the relevant XSLT resources rather than clutter up the Cocoon discussion lists.

Is (your description here) kind of functionality appropriate for a stylesheet?

When this kind of question arises, ask yourself:

• Am I using my stylesheet to address style concerns, or am I programming with it?
• Could I solve this problem once and for all during Generation?
• Isn't my problem better solved with a Transformer, since it requires coding?

There is not one, nor only one, answer. In Cocoon, you can accomplish the same thing in a number of different ways. Nonetheless, if your transformation depends on something specific happening during generation, it will be more difficult to reuse your code.

Here's a hint. Do all that you possibly can in a Generator. Add only what is absolutely necessary with Transformers. Use stylesheets to change format or style, not to code. This approach will make your system more manageable and reusable because it removes dependencies between components.

Can I use the same XSLT processor and still specify different processing options for different pipelines?

For example, I found that PDF processing is faster with Xalan when I turn incremental processing off.

Yes. For Cocoon version 2.0.3, check out the following Cocoon snippet.

Can I use different XSLT processors when processing different pipelines?

Yes. For Cocoon version 2.0.3, adapt the approach discussed in the following Cocoon snippet.

How can I remove namespaces from my xml files?

Sometimes adding xsl:exclude-result-prefixes attributes to the <xsl:stylesheet> or literal result element is not effective in removing all namespace declarations. For example, namespace nodes copied from the source document within <xsl:copy> or <xsl:copy-of> instructions (commonly found in catch-all stylesheet templates) will not be excluded.

There are two approaches to this problem.

One approach is to add a transformation step in your pipeline (or adjust your final stylesheet) with the following:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
    <xsl:template match="*">
      <!-- remove element prefix (if any) -->
      <xsl:element name="{local-name()}">
        <!-- process attributes -->
        <xsl:for-each select="@*">
          <!-- remove attribute prefix (if any) -->
          <xsl:attribute name="{local-name()}">
            <xsl:value-of select="."/>
          </xsl:attribute>
        </xsl:for-each>
        <xsl:apply-templates/>
      </xsl:element>
  </xsl:template>
</xsl:stylesheet>

Another approach is to extend your serializer component, described here.

What's "wrong" with use of the document() function in Cocoon?

Using the document() function for aggregation in Cocoon may break Separation of Concerns (SoC). That is, the designers of Cocoon view inclusion and transformation as different functions, best handled by separate Cocoon components. Treating them separately allows you to achieve performance gains and increases the resusability of your pipelines.

Alternatives to the document() in the Cocoon environment include aggregation or the use of a multi-stage transformation using the XInclude Transformer. This involves transforming a list of documents (generated dynamically or statically) by adding xinclude elements which reference (via xpointer) specific document content, and then transforming again via the XInclude Transformer, to obtain the desired result. For an example of this, see this email.

You'll achieve better performance if you aggregate content prior to transformation. This allows you to take full advantage of Cocoon's pipeline caching. In contrast, making dynamic document() calls inside an XSLT within a cached pipeline is problematic. At this time, Cocoon does not recognize changes in documents (called by the document() function) until the requested page expires from cache.

Understand that the document() function was designed *before* xinclude with xpointer facilities existed. Had such capabilities been available, perhaps the document() function, which essentially mimics xinclude and xpointer, would have never been added to XSLT.

Please note that if you must work with your XML files outside of the Cocoon environment, you may need to use the document() function in order to utilize the limited capabilities of other pipeline engines. This includes engines which are not xinclude-capable or which lack a predefined way to indicate document processing steps. If you are working with legacy code from non-pipelined engines, you may need to use the document() function as well, at least initially.

If you do use the document() function in Cocoon, you can still observe SoC by having separate XSLT stylesheets perform inclusion and transformation functions. For example, you can put multiple XSLT transforms in a pipeline and have the first one perform inclusion and the second one perform transformation. However, be mindful of some unresolved caching issues in Cocoon related to the document() function. At this time, Cocoon is unable to check validity of content included via the document() function. In addition, the document() function implemented by Xalan is inefficient. See: Issue 4257 and Issue 28341 Until this bug is fixed, consider using Saxon instead for document() function-related parsing needs.

For other aggregation/inclusion approaches, please stay tuned for XpathDirectoryGenerator (2.1 scratchpad), as well as Forrest's Libre (currently alpha in the Forrest cvs).