Taskdef fails with error: classname attribute of taskdef element is undefined

I have an Ant buildfile wit开发者_如何学Pythonh this line in it:

<taskdef name="for" classname="net.sf.antcontrib.logic.For" />

The build fails on this line saying:

classname attribute of taskdef element is undefined

I think this means that Ant cannot find the class file.

Where is Ant looking for this file? Where can I find it to add it to location X?

Q1: Where is ant looking for this file?

Insert these into your build.xml file:

<echo message="ant home is: ${ant.home}"></echo>
<echo message="user home is: ${user.home}"></echo>

(Source)

Q2: Where can I find it to add it to location X.

Enter the class name into http://www.findjar.com/