Hot-Loading Beans?

[gzoller]

Hey, ya'll...

I've got a requirement for an ability to hot-load beans as the XML files change. I was wondering if anyone in the community had already thought about this as a future feature before I look at making mods myself.

I was thinking that if I save the file and timestamp when a singleton is marshalled I should be able to check the file timestamp the next time the object is requested and reload it if its changed.

What I don't know yet is what effects this scheme will have on any lingering references to an old bean instance. Would they toss an exception if referenced? Hmm.... I might need some coding best-practices even if the hot-load works.

Cheers,
Greg

[Costin Leau]

Search the forums; for example:

http://forum.springframework.org/vie...ghlight=reload
http://forum.springframework.org/vie...ghlight=reload
http://forum.springframework.org/vie...ghlight=reload
http://forum.springframework.org/vie...ghlight=reload

What I don't know yet is what effects this scheme will have on any lingering references to an old bean instance. Would they toss an exception if referenced? Hmm.... I might need some coding best-practices even if the hot-load works.

There are some papers related to this issues and how the JVM reacts. Basically if you use interfaces and not a concrete class, the JVM will start using the new class once it's redeploy - the old classes will be used however until the reference is lost. I.E.

Client X requires class A v1.0.
You deploy class A v2.0
Client X still uses class A v1.0.
Client Y will get class A v2.0
Client X requires a new class A - gets v2.0.