Use pure Ant to implement if else condition (check command line input) - ant

Question

I am a newbie in Ant. My ant script receives a user input variable named "env" from command line:
e.g. ant doIt -Denv=test
The user input value could be "test","dev" or "prod".
I also have the "doIt" target:
<target name="doIt">
//What to do here?
</target>
In my target, I would like to create the following if else condition for my ant script:
if(env == "test")
echo "test"
else if(env == "prod")
echo "prod"
else if(env == "dev")
echo "dev"
else
echo "You have to input env"
That's to check which value user has inputted from command line, then, print a message accordingly.
I know with ant-Contrib, I can write ant script with <if> <else> . But for my project, I would like to use pure Ant to implement if else condition. Probably, I should use <condition> ?? But I am not sure how to use <condition> for my logic. Could some one help me please?

Answer 1

You can create few targets and use if/unless tags.
<project name="if.test" default="doIt">
<target name="doIt" depends="-doIt.init, -test, -prod, -dev, -else"></target>
<target name="-doIt.init">
<condition property="do.test">
<equals arg1="${env}" arg2="test" />
</condition>
<condition property="do.prod">
<equals arg1="${env}" arg2="prod" />
</condition>
<condition property="do.dev">
<equals arg1="${env}" arg2="dev" />
</condition>
<condition property="do.else">
<not>
<or>
<equals arg1="${env}" arg2="test" />
<equals arg1="${env}" arg2="prod" />
<equals arg1="${env}" arg2="dev" />
</or>
</not>
</condition>
</target>
<target name="-test" if="do.test">
<echo>this target will be called only when property $${do.test} is set</echo>
</target>
<target name="-prod" if="do.prod">
<echo>this target will be called only when property $${do.prod} is set</echo>
</target>
<target name="-dev" if="do.dev">
<echo>this target will be called only when property $${do.dev} is set</echo>
</target>
<target name="-else" if="do.else">
<echo>this target will be called only when property $${env} does not equal test/prod/dev</echo>
</target>
</project>
Targets with - prefix are private so user won't be able to run them from command line.

Answer 2

If any of you require a plain if/else condition (without elseif); then use the below:
Here I am dependent on a env variable DMAPM_BUILD_VER, but it may happen that this variable is not set in the env. So I need to have mechanism to default to a local value.
<!-- Read build.version value from env variable DMAPM_BUILD_VER. If it is not set, take default.build.version. -->
<property name="default.build.version" value="0.1.0.0" />
<condition property="build.version" value="${env.DMAPM_BUILD_VER}" else="${default.build.version}">
<isset property="env.DMAPM_BUILD_VER"/>
</condition>