[jbosscache-dev] Re: Cache Loaders and Non-String Fqns - Was: 2.0.0.BETA2

Manik Surtani wrote: > On 15 Mar 2007, at 18:24, Brian Stansberry wrote: >> Manik Surtani wrote: >>> I think we're going to need to support non-String Fqns. We're >>> not going away from that anytime soon. :S >> >> Good. I'm not positive, but I think the only place non-String >> Fqns are irreparably broken is with a preload call to a cache >> loader. > Well, any config file element that uses Fqns. Eviction policies, > for example. But that's a limitation on the config file, nothing > else. We should think about improving handling this for configurations built by a DI framework. >> With other cache loader calls, the real fqn is available as a >> call parameter, so the string-based representation used for the >> persistent store doesn't have to leave the cache loader. > Yeah, that can be worked around. What do you reckon the best > approach for "encoding" Fqns are, for CLs that only use Strings? > For each Fqn element, "Type:" + element.getClass() + ":value:" + > element.toString() ? Not sure why what we do now isn't sufficient (confession - haven't really looked).

> Could barf with user objects that don't override toString() and > you have object hash codes... > Yeah, if element.toString() doesn't provide a stable, unique id for element, then element's type is not appropriate for use in an Fqn with a cache loader. This is a bit complex, but can be summarized in a prominent doc page (and javadoc) on Fqn: 1) If cache is LOCAL with no cache loader, any Object will do. 2) If cache is replicated with no cache loader, any Serializable will do.

3) If a cache loader is used, for each type 'element' in the Fqn element.toString() must provide a stable, unique id for element. Default Object.toString() is no good; most (if not all) java.lang.Number classes are fine. A toString() impl that lists the class and the field name-value pairs for all the fields that go into an equals() evaluation is good. 4) If a cache loader is used and you want to use preload, the type must be String.