LinkageError is what you’ll get in a classic case where you have a class C loaded by more than one classloader and those classes are being used together in the same code (compared, cast, etc). It doesn’t matter if it is the same Class name or even if it’s loaded from the identical jar – … Read more
That will happen when you include server-specific libraries of a different server make/version in the /WEB-INF/lib of your web application, such as jsp-api.jar, el-api.jar, servlet-api.jar, etc. You need to remove them all. The /WEB-INF/lib should not contain any server-specific libraries. They belongs in the specific server itself (Tomcat has them in its /lib folder already). … Read more