Plugin references problem


I have just made my first SparkPlug, but I have a problem using it.

A few months ago I made a project in Java called OPO, in which I used Jena library. And now I use classes from OPO in my Spark plug!

But when I try to use plugin, I get ClassNotFoundException in log, saying that the classes from Jena lib are not available! I put OPO.jar in lib file for ant when I made plugin, and I also put Jena.jar library, but nothing! Does anyone have a clue how to fix this and make it work?