Using Ant how can I verify that ant-contrib.jar is avaiable in the ant lib before doing a build?

Question

Ant-Contrib is required for some parts of the build.xml so we first want to check if ant has the jar for it in its directory, and download and unpack it to the right directory if its not.

Any thoughts to this end is helpful

Answer 1

Look here to check if the file exists and here to download the file.