#3 Class cast exception in client - Inherited Interface

[Ian Ibbotson]

There is a problem when a factory object (f) which
declares a method as returning an instance of interface
(i) returns an instance of an object that inherits the
interface implementation from one of it's superclasses.
The attached code re-creates the problem. If you
comment out the "implements SessionInterface" from
ConcreteSession (Leaving the object to exted
AbstraceSession which itself implements
SessionInterface) then things go a bit wonky. If you
leave it so that both ConcreteSession and
AbstractSession implement SessionInterface then
everything seems to work fine. Found this whilst
working in JDK1.5 and I've got a sneaky suspicion that
it actually relates to a feature of java rather than a
bug per-se, but it's worth noting. In fact the crash
caused me to look at some of my code again and move the
interfaces around a little, so this is no longer a
problem for me.

Kind regards again for a cool project,
Ian.

[Ian Ibbotson]

Tar file containig some test code

[William Underwood]

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No, it's an issue with 1.4, and I think with 1.3 as well.

It's been a while since I looked at the code, but issue is
that the matching of exported and implemented interfaces was
broken: it only matches the first implemented interface
against the exported interfaces, and ignores interfaces
implemented through superclasses (easily fixed in the
library, replacing a block of code with an
aClass.isInstance(anObject) call).

[Joe Yandle]

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I fixed this bug in my local trmi source by adding the
following function to Naming.java:

public static Class[] getAllImplementedInterfaces(Object o) {
Vector<Class> interfaces = new Vector<Class>();
Class c = o.getClass();

while (c != null) {
for (Class i : c.getInterfaces()) {
interfaces.add(i);
}
c = c.getSuperclass();
}

Class[] ret = new Class[interfaces.size()];
interfaces.copyInto(ret);
return ret;
}

Then, call this function instead of
obj.getClass().getInterfaces() in Naming.java and
RemoteObjectWrapperImpl.java.