I'm using jsp:include -directive to include .html files as layout elements can change often. But when a form (using POST) goes to that JSP page I get error "Included servlet error: 405: HTTP method POST is not supported by this URL". That means that the included .html file does not support POST methods. When I change the form method to GET no errors are given and the file is included fine. Any ideas how I can support POST method forms too using this approach?
I'm not sure why your servlet engine is doing this... this is perfectly valid usage. Either file a bug report with your servlet engine vendor or switch engines.
As a work around, you should be able to rename your .html to .jsp. This will compile your HTML to a JSP (obviously), but a JSP always uses the service() method and this should avoid the bug in your servlet engine. Not ideal, but that should work.