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Re: [xsl] Confusing namespaces and xslt
2008-09-30 11:01:00
Evan,
Hmmm...the work-manager element isn't being added for some reason
for me using the snippet you provided. I like the "surgical" approach,
but I'm not sure why this snippet:
<!-- Append a <box:work-manager> element to the end of <work-managers>
content -->
<xsl:template mode="append" match="client:work-managers">
<box:work-manager>
<!-- etc. -->
</box:work-manager>
</xsl:template>
isn't running as expected. If I put in some debug statements the
work-managers element is being handled by the transform (with the
copy) later in your snippet, not but this focused snippet.
Paul
On Tue, Sep 30, 2008 at 10:28 AM, Paul <pflists(_at_)gmail(_dot_)com> wrote:
Thanks! That is very helpful.
On Mon, Sep 29, 2008 at 5:57 PM, Evan Lenz <evan(_at_)evanlenz(_dot_)net>
wrote:
I like to be as surgical as possible in my incremental transforms,
especially when I've got a lot of things to update. In this case, I might
use different modes, such as "content" and "append", as shown below:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
xmlns:client="http://somecompany.com/box/client";
xmlns:box="http://somecompany.com/box";
exclude-result-prefixes="client">
<!-- BUSINESS LOGIC: -->
<!-- Set the value for all <box:rotation-time> elements -->
<xsl:template mode="content"
match="box:rotation-time">newvalue</xsl:template>
<!-- Append a <box:work-manager> element to the end of <work-managers>
content -->
<xsl:template mode="append" match="client:work-managers">
<box:work-manager>
<!-- etc. -->
</box:work-manager>
</xsl:template>
<!-- GENERIC UTILITY CODE: -->
<!-- Identity transform for attributes, elements, comments, text, and PIs
-->
<xsl:template match="@* | node()">
<xsl:copy>
<!-- Everything here (inside <xsl:copy>) only applies to elements -->
<xsl:apply-templates select="@*"/>
<xsl:apply-templates mode="content" select="."/>
<xsl:apply-templates mode="append" select="."/>
</xsl:copy>
</xsl:template>
<!-- By default, just process the existing content -->
<xsl:template mode="content" match="*">
<xsl:apply-templates/>
</xsl:template>
<!-- By default, don't append anything -->
<xsl:template mode="append" match="*"/>
</xsl:stylesheet>
In other cases, I've also used "insert" (insert before existing content),
"before" (insert before the element itself), "after" (insert after the
element), and "att-value" (for updating just the attribute value, without
having to explicitly create a new attribute using <xsl:attribute> every
time).
Having such surgical precision can be very satisfying, but I don't usually
bother if there are only one or two things to update (as in this example).
But I thought I'd throw the idea out there anyway, in case you have lots of
things to update or you anticipate adding more update rules.
Evan
Wendell Piez wrote:
Paul,
At 03:44 PM 9/29/2008, you wrote:
What would be the best way to actually take the input xml transform it
into a new xml and just change a value or add a new element?
The best approach is to adapt the "identity transform", amending it with a
bit of extra logic to effect the changes you want.
This is a well-documented approach, once you know the keywords. As you
might imagine, an identity transform is one in which the output replicates
the input. Strictly speaking, what you are trying to write might be called a
"near-identity transform" -- this might be as simple as adding a template.
Would it be best to do a template match on "/" and do a for-each on
each element and then test each element to see if it was the one I
wanted to change?
No. It would be best to use template matching, as the standard identity
transform does. Its operation is fairly simple and straightforward, albeit
obscure if you don't know how XSLT templates work. But by the same token,
it's an excellent lesson in templates, which is indispensable for anyone
working with XSLT, and something you're much better off getting sooner
rather than later.
Use your favorite search engine to find writeups and you should be set.
Ask back here if what you find isn't enough.
Would it be better to set up specify template match statements for
each of the top-level elements and output the xml from the input
document except in the case where I need to change it?
Kind of ... the identity template (the heart of the logic) simply copies
input to output. Then, yes, you add templates to catch the cases where you
want to do something differently, like add or change or remove something. I
say "kind of" since the template matches all nodes, not just nodes at the
top level.
Cheers,
Wendell
======================================================================
Wendell Piez
mailto:wapiez(_at_)mulberrytech(_dot_)com
Mulberry Technologies, Inc. http://www.mulberrytech.com
17 West Jefferson Street Direct Phone: 301/315-9635
Suite 207 Phone: 301/315-9631
Rockville, MD 20850 Fax: 301/315-8285
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