Re: [Springframework-developer] Forcing dependencies between singleton beans without one actually being a property of another

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

Colin,
=20
I guess a "depends-on" attribute is clearer. <ref> is currently just =
used wherever objects can get passed in, i.e. in <property>, =
<constructor-arg>, <list>, etc. As dependencies can just be express to =
beans and not to values, the explicit <ref> element could be misleading. =
Furthermore, <bean>'s "parent" attribute also references another bean =
but not via <ref>. A dependency attribute with bean names as values =
would be similar.
=20
I've just added "depends-on" as attribute for <bean>, managed via =
RootBeanDefinitions's new "dependsOn" property. The value can be one or =
more bean names, separated by any number of spaces or commas. =
AbstractBeanFactory will simply call getBean for each of those names =
before creating the bean instance.
=20
Note that I do not recommend this for general usage but just for special =
cases like depending on prepared statics (*ugh*) or database preparation =
on startup. There could be the case of existing classes that work with =
statics. And for database preparation, it's hard to see why DAOs should =
have to reference that preparator as a bean property - they still depend =
on it being initialized and executed first, though.
=20
Juergen
=20

________________________________

Von: spr...@li... im Auftrag =
von Colin Sampaleanu
Gesendet: Di 11.11.2003 00:11
An: spr...@li...
Betreff: [[W3-SPAM]] - Re: [Springframework-developer] Forcing =
dependencies between singleton beans without one actually being a =
property of another - Email found in subject



As opposed to an attribute, you could re-use the 'ref' element, directly
under the 'bean' element to state a dependency. In fact, my colleage
didn't look too carefully at the dtd and tried to do that directly, to
get what he wanted. Having a 'dependency' attribute is probably clearer
though...


j=FCrgen h=F6ller [werk3AT] wrote:

>I've been asked that by co-workers too. In all our cases, we managed to =
solve the issue by redesigning the application objects so that such =
side-effects that other beans depend on are avoided. Nevertheless, I've =
repeatedly considered adding Ant-style "depends" support, possibly via a =
"depends-on" attribute of the "bean" tag, with a comma-separated list of =
bean names as value.
>
>On bean creation, the bean factory would simply have to call getBean =
for those bean names first, before actually creating the bean instance. =
That would be easy enough to add (compared to constructor resolution or =
such stuff), so I might do this alongside breakfast tomorrow ;-) Are =
there any objections to such an option? If not, I suggest to add this =
already for 1.0 M3.
>
>Juergen
>
>________________________________
>
>Von: spr...@li... im Auftrag =
von Colin Sampaleanu
>Gesendet: Mo 10.11.2003 23:26
>An: spr...@li...
>Betreff: [[W3-SPAM]] - [Springframework-developer] Forcing dependencies =
between singleton beans without one actually being a property of another =
- Email found in subject
>
>
>
>I had a co-worker ask me if there was a way to force the creation/usage
>of a singleton bean B to first create another bean, A, without A
>actually needing to be a property of B. He needs this because A has =
some
>side-effects which B depends on, to work properly.
>
>Of course there are some artificial ways to cause this to happen, but I
>can't think of anything too clean. Is this worth adding as a built-in
>capability?
>=20
>




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