On Sat, 15 Sep 2001, Bojan Smojver wrote:
> - if the jar file is changed, the application will reload (due to some
> recent fixes there in DependClassLoader), but some resources might not
> get loaded properly (for instance a properties file from within that
> jar)
What do you mean ( i.e. how do you load the properties ) ? We create a new
loader, and getting resources with the new loader should return the new
stuff ( I'm not sure for Bundles, maybe they're caching something - need
to check ).
> - if old version of the jar file, or a new jar file with the same binary
> of the class is returned back to WEB-INF/lib, sometimes the app will
> come back to normal after an automatic reload (not always though)
> - if you keep replacing jar file long enough with different versions, it
> will eventually fail even when loading class files from it and the whole
> app will stop working (ClassNotFoundException)
Again, need more details.
> I've checked the code in DependClassLoader and (unfortunately) it calls
> the parent's equivalent methods for getResourceAsStream() and
> getResource(), where parent is java.net.FactoryURLClassLoader. parent2
> is the same as class as parent, but different object (ie. another
> instance of the same thing). I'm guessing those things are part of the
> JDK.
DependClassLoader is a wrapper around the real webapp loader - it's role
is to record dependencies.
Parent is the real loader, parent2 is the grand-parent ( the parent of
all webapps ). If a resource can be loaded by parent2, it is loaded
( to respect the delegation rules ). If not, we get the resource from
parent ( i.e. from the application WEB-INF ).
The class is created by DependClassLoader so class deps will also go
to DCL ( and we can record them ).
URLClassLoader is the standard JDK1.2+ loader. It has some important
features besides loading classes - it checks sealing, load the right
security context, and many other things that are imporant.
You can of course replace it with anything you want - including
SimpleClassLoader or replacement. All you need to do is replace
LoaderInterceptor with your custom-made one.
> So, my real question here is, do any of you Sun guys (or any of you with
> better knowledge of JDK) know what this java.net.FactoryURLClassLoader
> actually does? Is it kind of 'caching' stuff and then it gets seriously
> confused when there are changes? Or maybe I'm doing something I'm not
> supposed to do...
If you can provide more details, I can take a look. Reloading seems to
work fine for me ( but I'll try again ).
> And finally, do we just write a replacement for this (probably buggy)
> method, or is there are known workaround or fix for this?
We must first find out which of the buggy methods we need to replace :-)
Costin
