Rafal,
It seems that the code below doesn't work as it was meant to. As
newInstance() is static, bootstrap() will not call the subclassed version of
it but the local one. Sorry to bother you so much with my small problem, but
a working solution would be to simply let the static instance member to be
protected either at the BaseServiceBroker level or at the TurbineServices
level. Then it's the task of the extending subclass to implement a safe
bootstrap() assigning the customized broker.
-- Ilkka
--
Nokia Networks
http://www.nokia.com/networks
mail: [EMAIL PROTECTED]
> -----Original Message-----
> From: ext Rafal Krzewski [mailto:[EMAIL PROTECTED]]
> Sent: 31. January 2001 13:17
> To: Turbine
> Subject: Re: [WISH] Services
>
>
> [EMAIL PROTECTED] wrote:
>
> > Something like this:
>
> > if (instance == null)
> > {
> > synchronized(TurbineServices.class)
> > {
> > if (instance == null)
> > instance = new TurbineServices();
> > }
> > }
> > return instance;
>
> > Would allow subclasses to assign their own service broker
> implementation to
> > the static instance member before getInstance() is called.
>
> This was done exactly this way until revision 1.14 of the Broker. Jon
> changed
> that to fix doble locking pattern. He posted an URL to an article that
> gives
> rationale for that.
>
> I think that right now TurbineServices should be the only
> real singleton
> in
> the system (correct me if I'm wrong). It is not instantiated
> spontaneously
> (on first use by the application code) but in precisely controled
> conditions.
> It is instantiated in Turbine.init() method which is internally
> synchronized,
> then it is bootstraped with essential services, then real
> configuration
> is
> loaded and finally all services are initialzed (in so called
> early init
> phase).
>
> I think that it would be justifable to lift the double locking pattern
> from
> the BaseServiceBroker class in the following way:
>
> public class BaseServiceBroker
> extends BaseInitableBroker
> implements ServiceBroker
> {
> protected static ServiceBroker instance = null;
>
> public static ServiceBroker getInstance()
> {
> return instance;
> }
>
> protected static ServiceBroker newInstance()
> {
> return (ServiceBroker)BaseServiceBroker();
> }
>
> /**
> * This method creates new ServiceBroker instance for the system.
> *
> * If there is an instance of ServiceBroker running, it will be
> * shut down.
> *
> * @param data The implementation dependent data used to create
> * the essential services.
> */
> public static synchronized ServiceBroker bootstrap(Object data)
> {
> if(instance != null)
> {
> instance.shutdown();
> }
> instance = newInstance();
> instance.initPrimaryServices(data);
> return instance;
> }
>
> public void abstract initPrimaryServices(Object data);
>
> //...
> }
>
> Implementations would have to override newInstance() and
> initPrimaryServices(Object)
> methods. Does this solution adress your concenrs Ilkka?
>
> Rafal
>
> PS. Thank you for the information concerning JMX. What paricular
> services in Turine
> did you chose to instrument as MBeans? I'm also interested in what
> adapters/connectors
> are you using, and if threre are any JMX enabled management
> applications
> available,
> other than Sun's RI?
>
> Rafal
>
> --
> Rafal Krzewski
> Senior Internet Developer
> mailto:[EMAIL PROTECTED]
> +48 22 8534830 http://e-point.pl
>
>
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