

Thomas Würthinger is a JVM hero - carsongross
http://guidewiredevelopment.wordpress.com/2011/05/06/the-dynamic-code-evolution-vm/

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nddrylliog
How about "A fully hotswappable JVM - never restart again"?

Also, VMs in the Smalltalk family have been doing this for a long time.

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carsongross
Sure. But JVMs haven't. (Unless you paid for something like JRebel, which has
its own issues.)

Thomas is a genius and extremely nice to boot. He deserves to be more widely
known.

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acidblue
I have tried many times to get JRebel to work properly. So, I gave up as the
docs are horrible. It (JRebel) uses an agent to do the hot swapping instead of
modifying the jvm.

I grabbed DECVM (and unfortunately I had to grab ICED Tea to run it on OS X,
so this limits my use) and it works wonderfully so far. The only thing that
JRebel does offer, that perhaps some of us will figure out for DECVM, is
reloading Spring configurations. Since a lot of us are using DI, the DECVM
tool only gets us to point, then the wonderful JVM restart has to happen.

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technomancy
Interesting.

While from a code licensing perspective there's no trouble with OpenJDK forks,
the patent licensing supposedly only holds for implementations that can pass
the compatibility kit, which Oracle has refused to let alternate JDKs run in
the past. I wonder if they have changed their tune for this or if they are
just looking the other way.

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akeefer
That is an interesting point . . . OpenJDK itself is covered by the patent
grants, but this is a patched version of OpenJDK. That said, the original
research done here was sponsored by Oracle, and Thomas now works in Oracle
Labs.

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paulbaumgart
Pardon the off-topic complaint, but why on earth would anyone put ads on a
company developer blog? Isn't the business rationale for a blog like this to
advertise the technical prowess of the company? In that case, is the ad money
really worth significantly cheapening the experience of reading the blog?

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akeefer
The ads were put there by wordpress, which we use to host the development
blog; we're not so immensely retarded that we'd explicitly put them on
ourselves to try to make money. Until recently (today? this week?) they've
never been there, so we didn't notice them or think to purchase the ad-free
version. As soon as someone on our team noticed this (about 5 minutes ago), we
purchased the no-ads upgrade.

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paulbaumgart
_we're not so immensely retarded that we'd explicitly put them on ourselves to
try to make money_

That's a relief. :P

I'll grudgingly admit I could have been a little more charitable in my
assumptions.

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fizx
Still gotta fix GC fragmentation before I'll never have to restart my JVMs.

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prexer
Yeah, never isn't a likely timeframe for JVM restarts, especially in
development, where the DCEVM really shines. You change some Java class, you
have your Tomcat server running, you get your new behavior on your web app
that you can test out right away without restarting Tomcat. It is a huge
productivity boost.

I'm not convinced that you'd want to use DCEVM in production.

