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From Alejandro Abdelnur <alejandro.abdel...@sun.com>
Subject a few enhancements for ant 1.4B2
Date Sat, 25 Aug 2001 01:23:34 GMT
hi folks,

i've been working with ant 1.2 for a while. i have implemented an ant
based development workspace for an iPlanet eCommerce application, taking
care of building, deploying and installing all the components of a j2ee
application (30K+ source files, including jsps, java, properties, xml,
etc.)

while designing an implementing this little monster i've run into some
limitations on ant 1.2 and we did some extensions to it.

i've finally had some time to download ant 1.4B2 and i've seen that many
of the issues have been addressed completely or partially, it took me a
couple of hours to port the extensions i did for 1.2 to 1.4B2.

from the implementation perspective, all this changes consist on adding
one or two new methods to the corresponding class and minor
modifications to existing ones to invoke the new ones (in ant 1.2 the
changes to get this functionality were much more complex).

following you'll find a list of these enhancements with a short
description..

i'll be glad to share these improvements and integrate them into the ant
code base if you agree so.

thxs and regards.

alejandro.

---------------------------------------------------------------------

list of enhancements:

    1* <target>, modified "if" and "unless" attributes
    2* <property> task, new "override" attribute
    3* <property> task, new "eval" attribute
    4* <antcall> task, new "iterate" and "iterator" attributes
    5* "*DEFAULT*" target name
    6* <ant> task, new "fallbackantfile" attribute


1* <target>, modified "if" and "unless" attributes

the value of the if an unless can be a property name (as it is right now
in ant) or a property name/value, i.e:

    <target name="tomcatDeploy" if="server.type=tomcat">

this target will only be executed if "server.type" is defined and and
its value is "tomcat"

this feature proved to be useful to execute targets depending on
properties values. for example depending on the server the developer is
deploying to (i.e. information stored in a properties file,
server.type=tomcat"). this contribute to reduce the number of entry
targets from the developer's perspective, in the given example a single
deploy target would invoke all the <SERVER>Deploy targets, only the one
matching the developer configuration will be executed.

2* <property> task, new "override" attribute

if present and set to true or false, the override attribute, allows to
change the value of an existing project property (user properties are
not affected).

this functionality works with all the flavors of the property task
(value, file, etc.)

an example for this is when loading global, group specific and
developers specific properties files:

    <property file="config/project.properties"/>
    <property file="config/${group}.properties" override="yes" />
    <property
file="config/${machine}/${developer}/${configuration}/user.properties"
override="yes" />

this allows groups and developers to override global (default) values.

3* <property> task, new "eval" attribute

the eval is a new way of setting a property (as value or file do). it
allows to assign to a property the value of other property, where the
name of the other property has been resolved in the build file, for
example:

    <property name="jmsHelper.name" value="jmsHelper"/>
    <property name="jmsHelper.version" value="0015"/>
    <property name="jdbcHelper.name" value="jdbcHelper"/>
    <property name="jdbcHelper.version" value="0014"/>

    <property name="module" value="jmsHelper"/>
    <property name="module.name" eval="${module}.name"/>
    <property name="module.version" eval="${module}.version"/>
    <property name="module.file"
value="${module.name}_${module.version}"/>

in the case of module.name, first the the eval attribute is resolved to
"jmsHelper.name", a property "jmsHelper.name" is looked up and if exists
its value is assigned to the module.name property.

4* <antcall> task, new "iterate" and "iterator" attributes

it allows to execute the antcall task in a looping way. the iterate
attribute contains the list (space separated) to iterate through, the
iterator attribute defines the name of the property that will contain
the element of the current iteration. for example:

    <target name="buildModule" if="module">
        <echo message="building module ${module}"/>
        ...
    </target>

    <target name="build">
        <property name="modules" value="frontend backend reporting"/>

        <antcall target="buildModule" iterate="${modules}"
iterator="module" />
    </target>

the antcall task will invoke the buildModule target 3 times, each time
the value of the iterator variable -module- will be set to "frontend",
"backend" and "reporting".

5* "*DEFAULT*" target name

if a target in the ant build file is named "*DEFAULT*", it will be
invoked if the invoked target does not exist. this provides a mechanism
similar to the default in a switch statement. a property named
"target.name" will contain the name of the invoked target.

    <target name="*DEFAULT*" depends="init">
        <echo message="Missing target [${target.name}] delegating to
custom.xml"/>
        <ant antfile="custom.xml" target="${target.name}"/>
    </target>

this provides a useful hook to delegate targets to other ant build files
without having to know them.

6* <ant> task, new "fallbackantfile" attribute

if present, the build file specified in the fallbackantfile attribute
will be used if the file specified in the antfile is not found.

    <target name="buildModule" if="module">
        <ant target="build"
            antfile="${module}/config/buildModule.xml"
            fallbackantfile="default/config/buildModule.xml"/>
    </target>

the fallbackantfile attribute provides a hook to customize parts of the
build process without changing the common build files.




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