Java's modules rock? (was Re: election details *PLEASE READ*)

Andreas Raab andreas.raab at gmx.de
Thu Mar 1 09:22:18 UTC 2007


stephane ducasse wrote:
>> In short: What impresses me about the Java solution is not that it's 
>> flawless - what impresses me is that it works, that people actually 
>> use it to deploy code and this code actually works in the way intended.
> 
> But do you think that VW, VA code does not work once deployed? I would 
> like to understand why Jar are better than parcels for example.

Here are some "simple" issues: How do Parcels deal with conflicting 
modifications to base classes? Say, one that says "Object>>isCommon 
^true" and one that says "Object>>isCommon ^false"? (Java simply doesn't 
allow modifications to base classes which, really, isn't such a bad 
thing from the point of view of modularity)

Another one: Which assurances do parcels give in terms of security? As 
far as I know there is no bytecode verifier, parcel have full access to 
the entire Smalltalk namespace (covered by ClassLoaders in Java), there 
are no limitations in terms of what operations a parcel can perform (nil 
become: true; Java had a good set of fixes in this area to get it right 
and not to leak ambient authority) and I don't think VW even knows what 
a sandbox is.

A third one: Which namespace are parcels loaded into? Can two different 
versions of parcels be loaded side-by-side? How (if at all) do they 
affect each other? Etc.

> May be I should post to VW to see what are the problem with deployed 
> code in VW.
> A parcel in VW has dev and depl prerequisites and it seems to work too.

Well, sure. Sorta. Kinda. :-) We can do the same in Squeak with projects 
and change sets and it seems to work, too. Sorta. Kinda. :-)

Cheers,
   - Andreas




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