Ant if else condition?

Solution 1:

The if attribute does not exist for <copy>. It should be applied to the <target>.

Below is an example of how you can use the depends attribute of a target and the if and unless attributes to control execution of dependent targets. Only one of the two should execute.

<target name="prepare-copy" description="copy file based on condition"
    depends="prepare-copy-true, prepare-copy-false">
</target>

<target name="prepare-copy-true" description="copy file based on condition"
    if="copy-condition">
    <echo>Get file based on condition being true</echo>
    <copy file="${some.dir}/true" todir="." />
</target>

<target name="prepare-copy-false" description="copy file based on false condition" 
    unless="copy-condition">
    <echo>Get file based on condition being false</echo>
    <copy file="${some.dir}/false" todir="." />
</target>

If you are using ANT 1.8+, then you can use property expansion and it will evaluate the value of the property to determine the boolean value. So, you could use if="${copy-condition}" instead of if="copy-condition".

In ANT 1.7.1 and earlier, you specify the name of the property. If the property is defined and has any value (even an empty string), then it will evaluate to true.

Solution 2:

You can also do this with ant contrib's if task.

<if>
    <equals arg1="${condition}" arg2="true"/>
    <then>
        <copy file="${some.dir}/file" todir="${another.dir}"/>
    </then>
    <elseif>
        <equals arg1="${condition}" arg2="false"/>
        <then>
            <copy file="${some.dir}/differentFile" todir="${another.dir}"/>
        </then>
    </elseif>
    <else>
        <echo message="Condition was neither true nor false"/>
    </else>
</if>

Solution 3:

The quirky syntax using conditions on the target (described by Mads) is the only supported way to perform conditional execution in core ANT.

ANT is not a programming language and when things get complicated I choose to embed a script within my build as follows:

<target name="prepare-copy" description="copy file based on condition">
    <groovy>
        if (properties["some.condition"] == "true") {
            ant.copy(file:"${properties["some.dir"]}/true", todir:".")
        }
    </groovy>
</target>

ANT supports several languages (See script task), my preference is Groovy because of it's terse syntax and because it plays so well with the build.

Apologies, David I am not a fan of ant-contrib.