On Windows systems, an application may use getClass().getResource or getResourceAsStream methods to locate a resource inside the application, particularly in jar files that are in the application or accessible to it. If the streams remain open, subsequent attempts to redeploy or undeploy the application can fail. In addition, the Java runtime by default caches streams to jar files for performance reasons.
Be sure to close streams opened by your applications. Also, if an application needs to be redeployed or undeployed repeatedly, and also needs to obtain a resource from a jar file using getResource or getResourceAsStream, consider using getClass().getResource, which returns a URL object, then invoke the url.setUseCaches method to turn off caching for that jar file, and use url.getInputStream() to obtain the stream.
Although turning off caching for access to the jar file can slow performance, this approach does allow the application to be undeployed or redeployed. Note also that if the getClass().getResourceAsStream method is used instead, then the jar file in which the resource is located is cached (this is the default Java runtime setting) and remains open until the server is stopped.