I've been experimenting with using JSP 2.0 tag files with Sling and have
run into a few quirks that I thought were worth sharing. I am hoping to
use tag files as an alternative to <sling:include> for small pieces of
standardized content (like a consistent date output style, or link
display). With <sling:include> I might need to create
SyntheticResources with resource types like standard/ui/date to do the
same thing (alternative suggestions welcomed :-)
The way I've found to get tag files to work is to create a WEB-INF/tags
directory under my Maven resources directory, and then configure the
/WEB-INF path as a bundle resource. This actually works great, and the
tag files are also picked up by the Eclipse JSP editor. The
disadvantages are you have to redeploy your bundle to update the tag
files; and there could be conflicts between bundles with identical tag
file names (not sure what the bundle resource provider does in this case?)
However, ideally, I'd like to be able to store these .tag files in the
repository, much like my resource type scripts, or other static
resources, and update them using WebDAV or cURL. The problem here is
that the JSP compiler requires that tag files come from only 2 places
(and their subdirectories): /WEB-INF/tags; or /META-INF/tags, if you
have a JAR-based TLD containing a <tag-file> element. Unfortunately,
you can't post content to /WEB-INF or /META-INF since they're protected
by the web container itself :-(
Lastly, you also can't use the /META-INF .tld method with a <tag-file>
element due to the way Sling handles bundle TLDs. The bundle listener
that registers them reports the location of a TLD as if the JSP page
referenced the .TLD file directly, even though you actually use the uri
attribute to reference it indirectly. This means the JSP compiler
doesn't keep track of the JAR file where the TLD comes from, and so
later has no way of finding the associated .tag files contained in it.
This might be fixable by having the SlingTldLocationsCache object return
the TLD location info as if the TLD is a JAR entry in the bundle JAR (if
and only if the TLD contains a <tag-file> element), but I'm not sure
it's worth it since deploying tag files from /META-INF is no more
convenient than the /WEB-INF method.
Regards,
Rory
