[#SPR-3509] better docs for "3.4.2. The prototype scope" wrt using them with singleton beans

Spring Framework

better docs for "3.4.2. The prototype scope" wrt using them with singleton beans

Created: 22/May/07 05:10 PM Updated: 23/May/07 10:39 AM

Component/s:

SpringCORE

Affects Version/s:

None

Fix Version/s:

2.1 M2

Time Tracking:

Not Specified

Description

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When you only read the contents of the chapter 3.4.2, you can get the impression that just defining prototype gets unique instances of a bean, in whatever context. Of course this is not true when using them within a singleton bean via method injection. It would be a time saver and a forum posts saver to make a hint to "3.3.8.1. Lookup method injection" directly in the description of what a prototype bean is.

Of course also some note that prototype has no effect when used by singleton beans in method injection mode would be nice.

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Rick Evans added a comment - 23/May/07 09:58 AM

Fixed. Thanks for raising this... I've added a small section to the end of the prototype section that explains the issue and has a link to the method injection section.

Cheers
Rick

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Taras Tielkes added a comment - 23/May/07 10:07 AM

What about the example used the manual to describe the "prototype" scope..

Does such a configuration (injecting prototypes into singletons using ctor/setter) actually *ever* make sense? I'm just curious if I'm missing some potential usage pattern.

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Rick Evans added a comment - 23/May/07 10:23 AM

Hi Taras

Good point... off the top of my head I can't think of a single really good use case.

Maybe Juergen knows some... in all my years of using Spring, I have never just injected a raw prototype in a raw singleton... so yeah, unless Juergen comments before this evening, I'll go add a note about that to the section that I just added.

Cheers
Rick

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Taras Tielkes added a comment - 23/May/07 10:39 AM

Hi Rick,

I haven't seen such usage either.
However, consider the example of a bean that implements a cache. Declaring one cache bean (with "prototype" scope) and injecting that dependency (using ctor/setter) into other beans will give each bean a unique, isolated cache instance.

For the sake of readability I would prefer multiple (inner) cache bean declarations, but above pattern might actually be valid (but confusing).