Re: Recommendations for working with LookupCache

Hi Mark

> ServiceItem is the data container for the service proxy and its meta
> data (lookup attributes and ServiceID). The lookup attributes might
> change while time progresses so there is no stable notion of a
> ServiceItem. In case you would pass in ServiceItem the lookup cache
> could only use the stable parts to determine the service (and its
> associated meta data) to discard. That would either be the ServiceID or
> the service proxy [1].
>
> In my experience in most cases, once obtained, you pass around the
> service proxy for computations and you don't remember the ServiceItem so
> it is more likely you have the service proxy object to discard than
> access to the ServiceItem.

Thank you, the clarification is helpful. In our case, the LookupCache
is conceptually "far away" from the clients of the service reference.
Thus I reasoned that the ServiceItem was more central to the cache
than the reference (as our factory is more interested in items than
references).

>
> BTW was the API for LookupCache not completely clear to you? In case
> ServiceItem was expected I would have also assumed the
> LookupCache.discard() method to take a ServiceItem object. Always be
> extremely cautious when a method takes an object as an argument ;-)

Unfortunately, the API threw me for a bit. I remember asking myself
some months ago what discard() actually applied to. We hadn't been
testing failure scenarios until now so I had never actually tested it.
You're right about the Object argument. I just assumed that because
the lookup() always returned a ServiceItem, the cache was based on
ServiceItems, not service references. Not thinking of equals(), I
wasn't sure how the LookupCache would perform a reverse lookup in its
cache (so to speak). I thought the Object argument was possibly there
to handle some Jini oddity. Oh well!  But in that sense I personally
find the API for discard() a little out of place compared to the other
methods in the class.


> [1] this assumes that in case of a specialized proxy a proper equals has
> been implemented or in case you have a pure Jini ERI proxy (or JRMP
> stub) this is taken care of automatically.

...and thanks for reminding me as well to take care of equals().


Regards
Patrick

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