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hi,
i'm trying to create a J3D VRML web browser viewer
with the vrml97 loader. i have it set up so that the vrml97.jar is
enclosed in my VRMLViewer.jar on "server" system. the "server" system also
holds the vrml data file (test.wrl). my "client" system (which the
browser will be running under) will have just Java3D installed (not the vrml97
loader). "client" will load up the VRMLViewer.html which will invoke the
VRMLViewer.class object in the VRMLViewer.jar archive and load the test.wrl file
up using the vrml97 loader that's also in the VRMLViewer.jar archive given to
the "client" from the "server".
when i do this, i get an AccessControlException
where i'm violating a RuntimePermission to createClassLoader. looking
further into the vrml loader source code, i realize that the VrmlLoader object
creates a URLClassLoader object based on the URL location on the Url of
where my "server" holds the test.wrl file is - the URLClassLoader is
triggering the AccessControlException. so i have a couple of questions
from that:
1) i understand that a class loader allows classes
to be loaded from elsewhere (ie another network domain). from the
code, it looks like vrml97 loader is setting up an URLClassLoader for the
test.wrl file. why does it need to do that? isn't a file stream just
be opened across the network to read in the test.wrl file for the loader or am i
just not understanding the code? or is it using the URLClassLoader to load
certain vrml97 class files from across the network from my "server" and that
violates Java security? if that's the case, why do we need to a
URLClassLoader since i've bundled the vrml97.jar archive in with the
VRMLViewer.jar archive which is downloaded to the "client" anyway.
couldn't the "client" just use the JRE's default class loader to load the vrml97
loader classes from it's own local space? again, am i just not
understanding how the JVM works?
2) if the URLClassLoader is absolutely necessary to
read in my test.wrl from the "server", can anything be done with the loading
code to allow the "client" to allow class loading. basically i'm looking
for solutions which require work on the "server" (ie code modifications, server
system settings, etc), but assume that the "client" is dumb and that nothing can
be done with the "client.
thanks for any input. i'm new with Java and
Java3D... still learning as much as possible.
jack
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