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From "Hoss Man (JIRA)" <>
Subject [jira] Updated: (SOLR-367) RFC: use contrete return types in analysis factory declarations
Date Thu, 27 Sep 2007 23:13:50 GMT


Hoss Man updated SOLR-367:

    Attachment: concrete.declared.returntype.factories.diff

my main motivation for this is a little project i'm working on in some spare time to try and
build a reflection based tool that will help us autogenerate Factories whenever we upgrade
the Lucene jar.  step one is identifying which TokenFilter and Tokenizer factories already
exist (even though the names might be inconsistent).  for that specific use case i could also
introduce some new annotations, but it got me thinking about this and i think it's a good
idea in general.  It makes the API of each factory self documenting about what that factory
produces, and makes hte javadocs a lot easier to follow.

no functionality is changed, and it is 100% backwards compatible.

i'm seeking comments before commiting however because it does violate the typical philosophy
of an API: declare that you return an interface/abstract class, not a concrete implementation.
 I'm not sure that is as important in the case of these factories.  it also (in theory) could
cause problems down the road if we start optimizing the factories.  ie: if we decide that
for certain input options, SynonymFilterFactory isn't going to return a SynonymFilter and
instead will return some new AliasFilter then in theory we have painted ourselves into a corner
unless this AliasFilter is a subclass of SynonymFilter because people might have written code
that directly calls the create method on the factory and expects a specific return type. 
likewise we might run into similar problems if we promote some of our own filters up into
lucene (and the packages change)

these seem like minor concerns however, given the intended usecase of these factories, and
the "self documentation" benefits of the API.

...but that's just my opinion, which is why i wanted to put it out there and see what people

> RFC: use contrete return types in analysis factory declarations
> ---------------------------------------------------------------
>                 Key: SOLR-367
>                 URL:
>             Project: Solr
>          Issue Type: Improvement
>            Reporter: Hoss Man
>         Attachments: concrete.declared.returntype.factories.diff
> will attach patch for comments: the main idea is to change most of the Tokenizer and
TokenFilterFactories to be explicit about what their "create" method returns instead of just
using "TokenStream"

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