I would suggest keeping proxies regardless of scope incompatibilities. In Wicket, we use proxies for injected references because of serialization issues (the pages/components are serialized out to disk). Most things that you're injecting aren't truly serializable (like DAOs and stuff). Now, we could re-inject dependencies upon deserialization, but that doesn't solve the problem either. Suppose a component passes its directly-injected, non-proxied reference to some other object that maintains that reference (a reference to a DAO for instance). Now, that object can't be serialized.
On Thu, Apr 2, 2009 at 11:56 AM, Mark Struberg <[email protected]> wrote: > > Hi! > > I'd like to write down a general idea about scopes and their interaction > which (after a talk with Pete) I think is 'implicitely' defined in the > JSR-299 spec. > > 1) If I inject a bean of a 'shorter' ranged scope into a bean with a 'longer' > ranged scope, then we have to use a proxy object. > > An example: We do need a proxy if an @SessionScoped bean has an > @RequestScoped bean as a member, because for every request, the > @RequestScoped bean member is different to the one from the previous request. > > We do _not_ need to use a proxy if the scope of the injected member bean is > 'equal' or 'longer' as the bean where it's a member of. > > 2.) Since the spec requires SessionScoped and ConversationScoped beans to be > Serializable, those 2 have to be injected via proxies only. > > Since JSR-299 gives anyone the possibility to write own Scopes, a simple > hardcoded scope comparison matrix is not sufficient. > To work around this, we may introduce a simple list of metrics in our > configuration, 1 for each known scope. Where a higher number means a longer > lifetime of beans of a scope. > > e.g. > scope.metric.RequestScoped=1 > scope.metric.ConversationScoped=2 > scope.metric.ApplicationScoped=3 > > If someone e.g. likes to introduce a WorkflowScoped (which typically is even > longer than applications since they may be persisted into a database and last > for years (kafkaesk indeed but possible)) it would get a metric of 4. > Another example: JSF has a 'FlashScoped' which would fit between > RequestScoped and ConversationScoped ... > > Open questions: > a.) can there be 2 scopes which are 'equally' ? > b.) is a simple ordered (comma separated) list sufficient? > > WDYT? May we get this plugable enough? > > LieGrue, > strub > > > > >
