Several years ago, we hired outsiders to write some custom code that ran OpenID for us. It resulted in a WAR that ran (perfectly, but as a black box) on jetty-hightide-7.6.5.v20120716. I have recently been ordered to upgrade this to work on jetty-9 (I'm using jetty-distribution-9.2.21.v20170120 to be precise). I dutifully set up the new server, and moved my WAR file with no changes. But now jetty complains that a certain class, com.mchange.v2.c3p0.ComboPooledDataSource, cannot be found, even though I can see the class in one of the JARS in the WEB-INF/lib directory. What gives? Is there a well-known process for moving a WAR file from one version of jetty to another? I have the source for the WAR file, so can rebuild it if necessary, though of course I don't have the source for all the dependent modules. But unfortunately, I lack a basic understanding of maven and jetty and the application itself.