FactoryBean support

[Martin Ellis]

Hi,

I'm looking at the support for FactoryBean beans in Spring ME.

As far as I can tell, FactoryBeans aren't supported when they are
defined as a top-level bean (i.e. they only seem to work when the
definition is nested inside another bean definition).

My understanding of the implementation is as follows:
* Nested (i.e. non-public or not 'top-level') instances are created in
a method named 'createXXX'.
* The 'create' method for FactoryBean beans always returns java.lang.Object.
* The results of all 'create' methods (FactoryBean or otherwise) are
cast to the type of the source when used.

I've been thinking about how to support FactoryBeans as top-level
beans. I don't think it makes sense to use the same approach of just
casting source values when they are used. Because an InstanceReference
doesn't contain a reference to the source bean, every single
constructor argument and setter argument would need to be cast (in
case it is a FactoryBean), which would make the generated code very
difficult to follow.

The solution I'd like to propose is to add a third pass (augmentation)
in the processing, that augments each 'sink' (constructor or setter
arg) to indicate whether a cast is required in the generated code.
Then, getXXX methods for top-level FactoryBean instances can declare a
return type of java.lang.Object, and these values would be cast at the
use-site. Hopefully, it would also be possible to consolidate some of
the code template, reducing duplication between public and non-public
instances.

The reason that the extra pass would be required is that the decision
of whether or not to cast at a given sink depends on the source, and
the QDoxAugmentation does not necessarily process the bean graph in
topological order of dependencies.

Does this make sense? Any other ideas? Should I prepare a patch?

Thanks,
Martin

[Paul]

Hi Martin,

This is basically a post to say keep up the good work! I'm not
actively involved with my use of Spring ME at the moment, and so
unfortunately the rusty knowledge I did have of it is wearing off!

Nevertheless, I *am* following this group and I will try and support
the project if and when I get the chance.

Cheers,
Paul.

[Martin Ellis]

On Mon, Mar 28, 2011 at 10:55 PM, Paul <paul...@gmail.com> wrote:
> This is basically a post to say keep up the good work! I'm not
> actively involved with my use of Spring ME at the moment, and so
> unfortunately the rusty knowledge I did have of it is wearing off!

Thanks for the support! :o)

Martin

[Martin Ellis]

On Sun, Mar 27, 2011 at 9:59 PM, Martin Ellis <mar...@contemplateltd.com> wrote:
> I'm looking at the support for FactoryBean beans in Spring ME.

I've now prepared a patch for this issue, based on the approach I described.

The last two commits of my topic/factory-beans branch are relevant:
https://github.com/mart/spring-me/commits/topic%2Ffactory-beans

The branch is based on my earlier pull request for alias support. If
that gets merged, then I'll tidy up and create another pull request
for the factory bean stuff.

Martin

[Wilfred Springer]

Hi Martin,

Sorry for not getting back to you on this. Awfully busy in my day job. (Did I say day job? It actually is starting to get a night job as well.) I *will* take a look at the changes you made. Perhaps tonight, but I will aim to look at it at least before the end of the week.

Wilfred

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[Martin Ellis]

Hi Wilfred,

On Wed, Mar 30, 2011 at 4:31 PM, Wilfred Springer <wil...@flotsam.nl> wrote:
> Sorry for not getting back to you on this. Awfully busy in my day job. (Did I say day job? It actually is starting to get a night job as well.) I *will* take a look at the changes you made. Perhaps tonight, but I will aim to look at it at least before the end of the week.

There's no hurry. I'm actually off on holiday from this Friday until
11th April, so whenever's convenient for you.

What's the easiest way to work? Do you want to review just the 'alias'
stuff as it is in master first?
Or would it be easier if I fix up the factory bean work and merge it
all into the same branch?

Martin

[Wilfred Springer]

Feel free to do a stab at it. I think it's fair to say that currently you are way more into it than I am. (Don't have too much muscle memory.) And it works out for you, there is a fair chance it works out for others as well. You are right about the limitations in FactoryBean support. And it would be awesome to have that fixed.

Martin

[Martin Ellis]

Here's what I've got:
https://github.com/wspringer/spring-me/pull/3

Works for me.™ :)

Martin