I think you will find it is actually executing, if you do some debugging. And you will find it thinks that param.username is null, because it is. You don't have a parameter called username. You do however have a request attribute called username, so you should change your code to use that.
You are using the <c:if> tag but I can't see anywhere that you have imported the tag.
Does it work with the following line added?
Feedback on general stuff in this JSP:
Your URLs are all absolute to localhost:8080. That is too much information. Theoretically they should just be local links - probably built with the <c:url> tag like you do for the scripts/stylesheets.