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https://issues.apache.org/jira/browse/OPENJPA-477?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12592687#action_12592687
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Patrick Linskey commented on OPENJPA-477:
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> What about making org.openjpa.kernel.exp expressions public? It could be
> convenient for
> developer's ExpressionFactories or ExpressionVisitors to identify the
> expressions being
> processed, or subclassing them.
The challenges with making them public are:
1. currently, they do actual real work -- i.e., they dig into the object model
to perform in-memory query parsing. This work is probably not desirable in most
implementations. Overriding the appropriate methods might do the trick, but is
dangerous; extenders would need to take care to override everything necessary.
2. making them extensible would potentially make it that much more painful if
we changed anything there. Basically, that would make those classes into part
of the implicit SPI in OpenJPA.
3. making them public would potentially encourage developing an inefficient
query processing engine, in which OpenJPA generated the AST and then the
back-end walked that AST. By encouraging back-end developers to put together
their own implementations of the interfaces, I expect that it's more likely
that the implementations will eliminate one graph traversal more regularly. Of
course, providing an invisible hand to encourage "good design" is not really
our business, so this is a secondary concern.
I think it would be useful to move all those classes into a new 'inmem' package
to get them out of the way and reduce clutter in that package, though.
> making StoreManager more flexible and extensible.
> -------------------------------------------------
>
> Key: OPENJPA-477
> URL: https://issues.apache.org/jira/browse/OPENJPA-477
> Project: OpenJPA
> Issue Type: Improvement
> Components: kernel
> Affects Versions: 1.0.2
> Reporter: Daniel Lee
> Fix For: 1.1.0
>
> Attachments: OPENJPA-477-trunk612523.patch, OPENJPA-477.613332.patch
>
>
> The OpenJPA StoreManager needs some modifications to make it more flexible
> and extensible. For example, some private methods and attributes need to
> made either public or protected. The attached patch identifies the areas
> that have been identified thus far. Please let me know if there are any
> concerns. Many thanks in advance.
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