 <p>The only way to use 2 different version of the same class is to laod them through 2 different classloaders. That is you have to load <strong>owls.jar__and __jena.jar</strong> with one class loader and <strong>envy.jar</strong> and <strong>jena2.jar</strong> with another. This solution has its own pitfalls, you should probably right custom code that will be able to use another classloader when it's necessary, maybe you will end up with writing your own class loader.</p> <p>As far as I know there is no built in solution for such situation. May be, it is easier to use older version of one the jar's above that can support the same version of <strong>jena.jar</strong> This is much easier solution.</p>