Hi,
I am writing to share my workaround for a gotcha I encountered with the latest
ant-contrib <for> tak (version 0.6) and some standard Ant tasks. And if anyone has a
better workaround/solutions, please let me know.
Consider a <for> loop like this, which does the following:
- loops over a fileset in a path
- derives the basename of each non-ejb jar in the fileset
- echoes the base jar name + a space char to a file that is later read-in to create
the ClassPath entry for the EJB jars manifest (not shown)
<for param="nonejbjar">
<path>
<fileset dir="${ear.root}">
<include name="*.jar"/>
<exclude name="*-ejb*.jar"/>
</fileset>
</path>
<sequential>
<!-- note the tricky ($) property
and (@) property use to uniquify the
basename property each time through the
loop -->
<basename property="[EMAIL PROTECTED]"
file="@{nonejbjar}"/>
<echo append="true"
file="${assembler.cache}/manifest.generated"
message="[EMAIL PROTECTED] "/>
</sequential>
</for>
The comment points out the tricky thing I had to learn today, which is that <for> can
have interesting side-effects when used with tasks that create properties. Which
essentially makes certain tasks unusable with the <for> task, or requires a tricky
workaround.
There's the trick I used for the <basename> task: each time through the loop, the
current value of @{nonejbjar} (from the fileset) is appended to the
${non.ejb.jar.name} property name, which tells basename to create a uniquely named
property each time through the loop. Here the property name is only used in the loop
to dereference the value in the <echo> task, so it doesn't matter what the name really
is. Note the nested [EMAIL PROTECTED] syntax to dereference the Ant property and the
macrodef attribute.
One alternative I considered was writing a regular expression using ant-contrib's
<propertyregex> instead of using the <basename> task. This task allows for overriding
the property name if it is already set. But then I found this was easier and a more
general solution.
An "override" attribute for some property-creating tasks like <basename> would be
pretty handy, I think.
Regards,
Scott Stirling
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