I tell ya, one of the things I love about Ruby, Python, Perl, etc… is that when you make a change to a the code or presentation layer, all you do is hit refresh in your browser.
With java and servlet containers it's a bit more difficult but can be almost as elegant if you know how to setup your dev environment properly. I'm often surprised by how many Java developers rebuild and redeploy the whole webapp for every change they make to say the domain model, a controller, or even simple JSP pages. Imagine changing a JSP, then sitting around for 15 seconds to a minute while it redeploys to make the change and then do that 100 times. It's a little too reminiscent of walking a stack of punchcards down the hall and quite frankly it's crazy, because as many know, there's a better way.
Here's how I like to address this issue is as follows.
1. Make sure you can build an exploded war and that when you rebuild, only updated classes, JSP files, etc… are copied into the exploded war. As a Maven user I do this with maven war:webapp, you can also do it with Ant or even better, through your IDE.
2. Make sure your servlet container knows to automatically check for and reload classes when they are updated in the exploded war. If you're a Tomcat user like me set the reloadable attribute in your Context to true. Never set reloadable to true in production!
3. Fire up Tomcat and mount the exploded WAR directory in Tomcat thought the manager application.
Now, make a change to class or JSP and run whatever command updates that class or JSP into the exploded WAR (e.g. ant, maven, or best of all setup your IDE to do it when you hit save). Hit refresh, Tomcat will detect the new class or JSP file and you'll see your results immediately.
Bottom line, even in Java you can update a class or view and see the results immediately by hitting refresh in your browser. It's just a bit more of a PITA to get setup initially!