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Re: [riena-dev] Riena-Singletons
Hi Stefan,

I dont think Services are Singleton. For example you can have multiple service instances for the same interface. I think OSGi Services are something like the way we use stateless remote services. Remote Services on the server are also used by many many users and are written so that they are thread-safe.

If we have OSGi Services in Riena they need to be stateless services (which might not be true today). I believe it would be the wrong approach to change the service model for the purpose of using RAP.....

just my 2 cent

christian

Am 16.09.2010 um 10:51 schrieb Liebig, Stefan:

Hi Rienars,
 
Aren´t OSGi services not some other kind of singletons?
I know they have a much nicer name but like a singleton a service exists only once in a JVM and can be shared from multiple clients.
If such a service has session dependent state we have to take care of it.
 
Does RAP provide any patterns for dealing with session dependent services?
 
Tschüß,
Stefan
 
Von: riena-dev-bounces@xxxxxxxxxxx [mailto:riena-dev-bounces@xxxxxxxxxxx] Im Auftrag von Liebig, Stefan
Gesendet: Montag, 6. September 2010 14:58
An: Riena Developers list
Betreff: [riena-dev] Riena-Singletons
 
Hi Rienaers,
 
While working thru our code base I have detected several kinds of "singletons" (some of them I would not call them a singleton):
1.       the classical singelton - a single instance of class (maybe created lazily or not) with the typical static getInstance() method (sometimes it has a different name) with fields (state)
2.       the static singleton - this a class with only static methods and static fields carrrying some state
3.       the pseudo classical singleton - a single instance of a class with getInstance() but without fields (state)
4.       the utility singleton - a class with only static methods without fields (state)
 
1. and 2. are "real" singletons (they have some state). At these singletons we need to look a little bit closer when we also want to use them within RAP. For them we can use SessionSingletonProvider and SingletonProvider.
 
How about 3. and 4., especially 3. ?
Should we transform 3 to 4 (no more getInstance(), just static methods)?
Or …
Should the getInstance() method always be named getInstance()?
 
 
Opinions, feedback, ..
 
Tschüß,
Stefan
 
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