[SOLVED] Trying to make this target conditional

Trying to make this target conditional

This is what I'm trying to do:

<target name="example">
   <if>
      <equals arg1="${var}" arg2="true" />
      <then>
         <exec executable="/bin/bash">
            <arg value="script.sh" />
         </exec>
      </then>
   </if>
</target>

And when I execute the target with ant example I get this error:

Problem: failed to create task or type if
Cause: The name is undefined.
Action: Check the spelling.
Action: Check that any custom tasks/types have been declared.
Action: Check that any <presetdef>/<macrodef> declarations have taken place.

I really need help in here. I would really appreciate it

Solution

That is because, if is custom task from ant-contrib library.

Make sure, ant-contrib library in your class path. Binaries can be downloaded from here. Extract the ant-contrib jar file to a location. And specify the same in below taskdef.

Then add the taskdef at the beginning of the build.xml. Refer documentation for more details.

For eg:

<taskdef resource="net/sf/antcontrib/antcontrib.properties">
    <classpath>
        <pathelement location="/absolute/path/to/ant-contrib-1.0b3.jar" />
    </classpath>
</taskdef>