A file containing code for customizing a server's functionality can be “hot plugged” into the server without requiring server restart. The file is added in a class path of its own. The server's class path is not modified during this process, and, consequently, the server does not need to be shut down or restarted. Changes are made to the class-loading pattern of a JVM. Whenever the JVM starts, the JVM's own container class loader component loads the classes. Custom plug-in jar file code is loaded by a parallel class loader that executes in parallel with the container class loader. When the parallel class loader is started, the container class loader is made the parent of the parallel class loader. Because the container class loader is made a super class of the parallel class loader, components loaded by the parallel class loader become recognized by the parent container class loader.