GERODOLLE Anne FTRD/DTL/GRE wrote:
> Hello,
>
> I have a small question concerning Jeremie stubs.
>
> As far as I have experienced, two stubs corresponding to the same remote
> object are considered "equals", but do not return the same hashCode.
>
> Note that two different java.rmi stubs to the same remote object return the
> same hashcode.
>
> Is that a bug ?
Apparently, yes. Two equal objects must have the same hashcode.
Actually, the main difficulty is to check that two stubs correspond to the same
remote object, because it requires comparing remote identifiers that are not
necessarily comparable. In old versions of Jonathan, two stubs were not
considered equal. But this was corrected quite a long time ago because Jonas
needed it (to store objects in hashtables), through the implementation of an
ad-hoc conservative mechanism, that ensures that if the equals() method returns
yes, then the target objects are certainly equal. But, to my knowledge, the
hashcode was always coherent with the result of the equals() method.
If I remember well, the equals and hashcode methods are computed by the
Reference object designated by the stub, not by the stub itself. Two different
Reference implementations are available in Jeremie : one is present in the
StdStubFactory (used by JIOP, thus in the classical client/server case), the
other in the EventChannelFactory. In which case did you experience the problem
?
> What would be the best method if I want to build a hashtable
> associating some values to remote objects ?
Jonas already does something like that, and it works...
> I can imagine some methods, like
> using a key that is a "stub wrapper" :
> class StubWrapper{
> Object contents;
> public boolean equals(Object other) {
> if (! (other instanceof StubWrapper)) return false;
> if ( ((StubWrapper)other).contents.equals(contents)) return
> true;
> return false;
> }
> public int hashCode(){ return 0;}
> }
>
> but it does not look very nice...
Indeed...
I will have a look at your problem anyway. Which version of Jonathan are you
using ?
Bruno
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