I ran into what seems to be the infamous "failed to execute pipeline" problem
with Cocoon 2.1.2 in trying to execute a simple XSLT transform. Doing some
googling led me to believe that I'm not the only one that has been puzzled by
this bug.
Eliminating the transform from the pipeline and serializing directly to XML
showed well formed XML going into the transform step, which was very
frustrating, so I put in a logging transform. Lo and behold, the logger
showed that the startDocument and endDocument SAX events were doubled up!
What caused this problem is that I had set a session attribute (in a custom Action) to
hold the XML document I wanted
transformed, but I had set that attribute to be the DOM Document object, then used
SessionAttributeGenerator to create the SAX event stream for the transformation. This
should be
perfectly acceptable!
Problem is that the generate() method in SessionAttributeGenerator looks as follows:
public void generate() throws IOException, SAXException, ProcessingException {
xmlConsumer.startDocument();
if (this.elementName != null) {
xmlConsumer.startElement("", this.elementName, this.elementName, new
AttributesImpl());
XMLUtils.valueOf(xmlConsumer, this.attrObject);
xmlConsumer.endElement("", this.elementName, this.elementName);
} else {
XMLUtils.valueOf(xmlConsumer, this.attrObject);
}
xmlConsumer.endDocument();
}
The bug is evident because if the this.attrObject is set to a Document object (rather
than the
document root Element), the method generates a start/end document....but so does the
interior code!
So you get duplicate start/endDocument events generated and downstream XSLT transforms
barf on the
input (funny that the XML serializer doesn't much care about this duplication).
Anyway, rewriting the generate() method of SessionAttributeGenerator will correct this
insidious
bug:
public void generate() throws IOException, SAXException, ProcessingException {
if( !( attrObject instanceof Document ) {
xmlConsumer.startDocument();
}
...same interior code as before
if( !( attrObject instanceof Document ) {
xmlConsumer.endDocument();
}
}
I've posted this bug fix to the Cocoon dev list, and hopefully one of the
developers will incorporate it into 2.1.3, thereby saving some else some
serious headaches in tracking down this bug.
In the meantime, the quick workaround (if you don't want to change the Cocoon
source and rebuild it) is to just set your session attribute to be the root
element of the document rather than the document itself. For example, if
you're code has a Document object called doc, then do something like this:
session.setAttribute("my-attribute", doc.getDocumentElement() );
instead of:
session.setAttribute("my-attribute", doc );
which will cause the bug to manifest.
Just thought I would pass on the info....
Andrzej Jan Taramina
Chaeron Corporation: Enterprise System Solutions
http://www.chaeron.com
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