Adding JAR to eclipse project

I am trying to use JTidy on google app engine. In Eclipse, I add JTidy jar to the b开发者_如何学Cuild path and add the jar again as the source attachment. When I make a tidy object it shows up as a org.w3c.tidy.Tidy. but when I run my app i get the error java.lang.NoClassDefFoundError: org/w3c/tidy/Tidy. Am I not adding the jar correctly? Does JTidy not work on google app engine?

The JAR needs to be added to the lib folder in war/WEB-INF

Add the jar to war/WEB-INF/lib and also right-click on the project, configure build path. Their add external libraries.