maninder batth wrote:
> 1. Customer goes to stamp counter and asks for stamp cost for a particular
> country.
> Counter person responds with cost. Customer hands the money and envelope and
> counter person hands back change if any.
This is an interesting example which can show the power of the Jini programming
model and mobile code used to implement smart proxies.
In a Jini solution to this problem, the client might contact the lookup
service,
asking for a "Postman" interface implementation. The returned Postman could be
a smart proxy which might include a local cache of popular country stamp costs.
To send a letter, the client would use the smart proxy to ask for the price of
the stamp for a particular country. Through the use of a smart proxy, the
costs
query would be a local method call, instead of a remote exchange. Once the
stamp cost was known, the appropriate payment transaction in concert with the
transport of the "letter" would take place as a single remote exchange. That
transaction might also encapsulate the chosen country so that the service could
increment the popular country counters to manage its caching of values sent
back
with the smart proxy.
The smart proxy might use a lease on the pricing so that expired prices would
be
refreshed automatically without the client having to account for that behavior
in the implementation details.
The mobile code model allows for such local vs remote optimizations to be made
independently of the client implementation and to change over time without the
client having to have implementation changes.
This model applies in many other situations, and is quite powerful for many
types of applications.
Gregg Wonderly
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