[Springframework-developer] RE: Question about Bean Factories - the Singleton attribute/property

[<jue...@we...>]

Effectively, FactoryBean.isSingleton just gives a hint whether getObject =
will return a cached singleton or a new instance on each call. =
Currently, this is just evaluated for getBeansOfType checks. The =
singleton flag of the bean definition on the other hand determines how =
the bean factory treats the FactoryBean itself.

If the FactoryBean is not a singleton, each reference to it will create =
a new FactoryBean in the bean factory. That instance can in turn return =
an internally cached singleton on getObject or a new object on each =
call. Obviously, a non-singleton FactoryBean that returns a singleton =
object does not make much sense.

So if you implement FactoryBean.isSingleton =3D false and =
correspondingly create a new instance on each getObject call to your =
FactoryBean, bean references will always get a new object. Making the =
FactoryBean itself a singleton too is orthogonal to this; you will =
almost always have it as singleton.

So there are two independent singleton statuses involved:
- the one of the FactoryBean: Should the bean factory create a new =
FactoryBean on each reference?
- the one of the object created by the FactoryBean: Does the FactoryBean =
create a new object on each getObject call?

Juergen


-----Original Message-----
From: spr...@li...
[mailto:spr...@li...]On Behalf
Of Cameron Braid
Sent: Tuesday, November 04, 2003 4:06 PM
To: spr...@li...
Subject: [[W3-SPAM]] - [Springframework-developer] Question about Bean
Factories - the Singleton attribute/property - Email found in subject


I am implementing a bean factory that is not a singleton.

There are two places where I can specify this property :

1) in the <bean singleton=3D"true|false|"> tag
2) in the boolean FactoryBean.isSingleton()

The doco states :

  The singleton status of the FactoryBean itself will
     * generally be provided by the owning BeanFactory.

Please explain how this works.

If I implement isSingleton =3D false, then someone configures <bean ...=20
singleton=3D"true" >  what will happen ?

Thanks,

Cameron

--=20
Any damn fool can write code that a computer can understand...
The trick is to write code that humans can understand.
[Martin Fowler =
http://www.martinfowler.com/distributedComputing/refactoring.pdf]





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