How do you automate Javascript minification for your Java web applications?

I'm interested in hearing how you prefer to automate Javascript minification for your Java web apps. Here are a few aspects I'm particularly interested in:

How does it integrate? Is it part of your build tool, a servlet filter, a standalone program post-processing the WAR file, or something else?
Is it easy to enable and disable? It's very unfunny to try and debug a minified script, but it's also useful for a developer to be able to test that the minification doesn't break anything.
Does it work transparently, or does it have any side effects (apart from the ones inherent in minification) that I have to consider in my day-to-day work?
Which minifier does it use?
Does it lack any features that you can think of?
What do you like about it?
What don't you like about it?

This will mostly serve as a reference for my future projects (and hopefully other SOer's will find it informative, too), so all kinds of tools are interesting.

(Note that this is not a question about which minifier is best. We have plenty of those around already.)

Solution

Round-up post

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