Originally by @hesara

See also #14146

Originally by mrbrush

I propose a patch to this issue, so that the cache staleness checking mechanism also considers URIs pointing to classloader resources which themselves are located as files in the filesystem (typical for maven based dynamic web projects with the Serve modules without publishing option checked in the Tomcat server config in Eclipse).

#!patch
--- VaadinServlet.java	2014-12-05 01:46:50.649265500 +0100
+++ VaadinServlet.java	2014-12-05 02:19:58.627971400 +0100
@@ -77,6 +77,13 @@
             long newest = 0;
             for (String uri : sourceUris) {
                 File file = new File(uri);
+                if (!file.exists()) {
+                	//try finding it through the classloader
+                	URL url = getClass().getClassLoader().getResource(uri);
+                	if (url != null) {
+                		file = new File(url.getFile());
+                	}
+                }
                 if (file.exists()) {
                     newest = Math.max(newest, file.lastModified());
                 } else if (!uri.startsWith("VAADIN/")) {

Originally by mrbrush

Hmm, maybe also check for the URL's protocol, if it's file because it could also be something else.

Originally by @Legioth

Replying to mrbrush:

I propose a patch to this issue, so that the cache staleness checking mechanism also considers URIs pointing to classloader resources which themselves are located as files in the filesystem (typical for maven based dynamic web projects with the Serve modules without publishing option checked in the Tomcat server config in Eclipse).

Could you please create a separate ticket for this case, since this ticket has been closed for a while already.

If you want, you can also directly submit a patch to our code review system: https://vaadin.com/wiki/-/wiki/Main/Contributing+Code