link: http://www.neiland.net/blog/article/how-to-install-ant-contrib/
Step 1: Get ANT-Contrib And Install It
So lets get started installing them. Go to the ant-contrib download page on sourceforge and get the 1.0b3 version zip file. Extract the zip file and copy "ant-contrib-1.0b3.jar" to your "{ant install dir}/lib" folder.
Step 2: Configure Your Project
With the jar file installed in the ant lib directory the next step is to include the ant-contrib tasks in your project. To do this add a taskdef entry to your build file init code. The format of this depends on the version of ant you are running.
Ant >= 1.6
<taskdef resource="net/sf/antcontrib/antlib.xml"/>
Ant < 1.6
<taskdef resource="net/sf/antcontrib/antcontrib.properties" />