[hibernate-issues] [Hibernate-JIRA] Commented: (HSEARCH-618) BridgeFactory should pass along the field type to the field bridge constructor (if an appropriate constructor exists)

[Emmanuel Bernard (JIRA)]

    [ http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=39047#action_39047 ] 

Emmanuel Bernard commented on HSEARCH-618:
------------------------------------------

I'd favor an interface.

interface ReturnTypeAwareBridge {
  void setReturnType(Class<?> returnType);
}

But maybe the class is not enough and the generic metadata API would be preferable (though extremely non intuitive).

Anybody up for a contribution (for the Class<?> version)?

> BridgeFactory should pass along the field type to the field bridge constructor (if an appropriate constructor exists)
> ---------------------------------------------------------------------------------------------------------------------
>
>                 Key: HSEARCH-618
>                 URL: http://opensource.atlassian.com/projects/hibernate/browse/HSEARCH-618
>             Project: Hibernate Search
>          Issue Type: Improvement
>    Affects Versions: 3.3.0.Beta2
>         Environment: Hibernate Core 3.6.0
>            Reporter: I D
>            Priority: Minor
>
> Currently, only the built in EnumBridge is getting access to the field type via its constructor.
> That's a shame, since the field type is very useful information, and may be necessary for certainy types of bridges, plus it's readily available to the BridgeFactory.
> Here's one use case:
> Suppose I want to create a bridge named EnumOrdinalBridge, similar to EnumBridge but saving the constants' ordinals to the index (instead of their names/values). This bridge would need to know the Enum type, so the only way this could be done presently is to make it a ParameterizedBridge and then to pass the enum's class name via the "params" param of the @FieldBridge annotation.
> Here is how an invokation of such a bridge would look:
> {code}
> public enum Gender {MALE,FEMALE}
> {code}
> {code}
> @Field(index = Index.UN_TOKENIZED)
> @FieldBridge(impl = EnumOrdinalBridge.class, params = {@Parameter(name="class", value="package.name.Gender")})
> public Gender getGender() {
> 	return gender;
> }
> {code}
> Note the problematic use of qualified class name as a string literal - this is neither portable nor refactoring-proof. What if I wanted to change the name of the enum or move it to another package (or what if I simply misspell the qualified class name)? These will all lead to runtime (rather than compile-time) errors. Also, repetition's bad (m'kay?), so there's no reason to have to explicitly pass along information to the bridge when that information is already implicitly available to the BridgeFactory.
> I suggest you use reflection in BridgeFactory to detect whether the constructed FieldBridge has a constructor with one argument of type Class. If so - that constructor will be used (instead of the no-args constructor, currently used for all non-built-in field bridges), and the type of the field will be passed as its argument.
> With this behavior implemented, the above example can be nicely reduced to the following, and we'll have achieved code portability and enhanced compile-time safety:
> {code}
> public enum Gender {MALE,FEMALE}
> {code}
> {code}
> @Field(index = Index.UN_TOKENIZED)
> @FieldBridge(impl = EnumOrdinalBridge.class)
> public Gender getGender() {
> 	return gender;
> }
> {code}

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