So by null object, you mean an object which implements the LogService
interface but whose methods are no-ops?
BJ Hargrave
Senior Technical Staff Member, IBM
OSGi Fellow and CTO of the OSGi Alliance
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Marcel Offermans <[EMAIL PROTECTED]>
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2006-05-11 10:16 AM
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Re: [osgi-dev] Declarative Services implementation guidelines?
Kevin Riff wrote:
>Copying to a local variable first would also work, but only if the log
>field is volatile. Otherwise you risk having your threads see a stale
>copy of that field.
>
>
>-----Original Message-----
> // ...
> if(log != null) {
> log.log(LogService.INFO, "Did something");
> }
> // ...
>
>
In the dependency manager I've used the null object pattern to make this
a bit easier for the user. Instead of "nulling" the field when the
service is not available, I create a null object so you don't have to
check for null everywhere. Of course you should use this combined with
the volatile keyword, like Kevin suggested.
The null object implementation I've used should be pretty easy to re-use
(even if you don't use the dependency manager).
Greetings, Marcel
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