[hibernate-dev] [HSEARCH] Autodiscoverable field bridges next steps

[Emmanuel Bernard]

Please everyone and especially Sanne, read this branch of the exchange Hardy and I have. We need another pair of eyes to make sure we don’t mess things up as it is an important departure compared to how things are done today (and in my prototype).

Hardy, I am starting to come along your side on this discussion. They key things that made me swing is that if a user needs a special annotation to customize the bridge, then it’s equivalent to a @FieldBridge. So a feature like CDI stereotypes or BV’s composition (by annotating a custom annotation with a @FieldBridge) would solve that problem more elegantly.

I am still a bit sceptical to move the bridge discovery to AMP - at least when explicit annotations are at play because:
- AMP is complex
- BridgeFactory seems a nice focal point to everything bridge related
- a few common rules must be applied to bridges (like the IterableBridges / MapBridges and ArrayBridges wrappers)

Nevertheless the idea of inferring types via @FieldBridge, @TikeBridge, @DateBridge, @Spatial in a separate method than guessType has merits.

BUT

In practice for Date related add-ons like JodaTime and Java 8 date, I am wondering if we should ensure that someone can use @DateBridge. After all a resolution is likely conceptually needed and forcing another annotation seems wrong.
Likewise for "Hibernate Spatial” types, it will probably make sense to support them as annotated with @Spatial like we do for Coordinates.

So what do we do about there?

- are they legit use cases (I think they are)
- is that supposed to be supported by some other features unrelated to BridgeProvider?
- should we design BridgeProvider in a way that let them react to these built in annotations? (via explicit methods I suppose).

Emmanuel

PS: I’ve spend around 20hrs on that feature so if we could converge, that would be good :)

On 02 Apr 2014, at 21:18, Hardy Ferentschik <hardy at hibernate.org> wrote:

> 
> On 2 Jan 2014, at 17:37, Emmanuel Bernard <emmanuel at hibernate.org> wrote:
> 
>> Yes your analysis is correct.
> 
> Cool, so we seem to be on the same page then.
> 
>> I do think 3 is the most valuable but that 2c is a relatively close second.
> 
> +1 for case #3 being the most important one. I would even go so far to say that this is the only one we should address with the BridgeProvider.
> 
>> Now the @Spatial and @TikaBridge annotations do have attributes which will influence how the underlying bridge is created.
>> I don’t think you are proposing to move the spatial and Tika bridge creation up on AnnotationMetadataProvider.
> 
> That’s what I am proposing. Also the processing of the @Bridge annotation (standalone or as part of @Field) should move. Really 
> what happens in BridgeFactory#findExplicitFieldBridge (which is funny enough called by something like BridgeFactory#guessType)
> is annotation and hence AnnotationMetadataProvider specific. BridgeFactory#guessType could really just become the handler of the described scenario 3.
> 
>> That would AFAIU duplicate the bridge creation logic between the AMP and some ProgrammaticMetadataProvider.
> 
> No, not really or at most temporarily. Remember, using commons annotations and pseudo annotations are just a crutch. It would be much easier to
> instantiate the right metadata and bridges directly. After all the user does explicitly something like .property( "name", ElementType.FIELD ).spatial()
> There is not need to guess, you could create the appropriate bridge directly. 
> 
>> Also I have a hard time navigating and understanding AnnotationMetadataProvider, so I’m not sure we should make it more complex.
> 
> Sure AnnotationMetadataProvider is a lot of code, but it is actually still very similar to the code you originally wrote for DocumentBuilder. It just has moved.
> An indexed class is processed by creating the class hierarchy for this class and then iterating the class hierarchy finding indexed properties. You should
> be able to follow the  flow quite easily from AnnotationMetadataProvider#initializeClass. Also have a look at the call sites for BridgeFactory#guessType.
> 
>> So somehow, the AMP should convert @Spatial, @NumericField, @TikaBridge, and @DateBridge into some non annotation based representation and pass that information to the bridgeFactory.
> 
> Somehow you would create the bridge directly. Either from the AnnotationMetadataProvider or we need some additional methods on BridgeFactory.
> 
>> Your approach would be to call explicitly buildXxxBridge() - like buildDateBridge() - methods form AMP.
> 
> That would be one way of doing it. If these methods would be in BridgeFactory they could even be called from the programmatic config
> 
>> These would be hosted on the BridgeFactory. Is that correct?
> 
> Right
> 
>> And the same explicit call logic would be done on a programmatic API equivalent.
> 
> Right
> 
>> Now how would you pass and to these kind of explicit calls in the 2c case when the annotation is unknown a priori?
> 
> A couple of things here.  buildXxxBridge() are specific to our internal bridges (date, spatial, tika). There is no equivalent for custom (user provided) bridges. They are either 
> explicitly configured or go via the BridgeProvider contract. If we truly want to support 2c, we need something like the AnnoatedElement in the contract of BridgeProvider.
> On the other hand, 2c can also be solved by the user by specifying his bridge directly. 
> 
> If we just think about case #3 BridgeProvider could almost become:
> 
> FieldBridge returnFieldBridgeIfMatching(Class<?> returnType, ServiceManager serviceManager);
> 
> For me it has many benefits:
> 
> 1)  It separates completely the annotation processing from the bridge creation, something which is currently in the way for a refactoring of the programmatic config and probably a problem
>     for non entity based indexing
> 2) Probably future proof for non entity based indexing
> 3) From a development point it treats case #1, #2a and #2b the same way - as explicitly known bridges (which is really the case)
> 4) There is no major loss in functionality
> 
> —Hardy
> 
>