JEP 220: Modular Run-Time Images

mark.reinhold at mark.reinhold at
Thu Oct 30 23:17:20 UTC 2014

2014/10/30 3:42 -0700, Tim Boudreau <niftiness at>:
> Ditching JAR file format is going to wreak havoc with IDEs, build tools and
> any sort of analysis tool that utilizes javac's API or internals (I've
> written some), or anything that looks for the .jar file extension.

Yes, we know.  That's why we've been talking about this publicly for a
couple of years now and why we're offering a sane replacement, the jrt:
URL scheme, which can even be used on JDK 8.

> I agree with the need for a replacement (though technically, you could put
> whatever precomputed structures you want in a JAR, just not as efficiently
> as is desirable), but it seems like something that's a little big for a
> line-item in a proposal about something else.

This change is part and parcel of the move to modular images.  I don't
see much point in breaking it out into a separate JEP -- which would be
very short anyway, since we're not defining a (documented) format to
replace JAR files.

> A non-disruptive approach would be to keep the file extension and enhance
> JarInputStream et. al. to transparently treat new JARs as if they were old
> JARs.  Is something like that being considered?


The JAR format has run its course.  It's time to move on.

- Mark

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