[hibernate-dev] HSEARCH-3000 Pick Jigsaw Automatic Module names for all published modules

[Gunnar Morling]

2018-02-12 17:55 GMT+01:00 Sanne Grinovero <sanne at hibernate.org>:

> Picking automatic module names for Hibernate Search isn't going to be
> straight-forward as our two main jars (hibernate-search-engine &
> hibernate-search-orm) suffer from split package among them.
>
> We can't really fix the split package problem without breaking all
> users, so if we want to consider that, we can debate it but that will
> need to happen at another round as we're doing a minor release, so
> let's focus on:
>  # Which names to pick
>  # Should we pick the names at all
>  # Which modules should have a name
>
> For a great background on the possible strategies and pitfalls I
> recommend reading Stephen Colebourne's blog on this subject [1].
> He persuaded me there are good reasons to use the "reverse DNS, the
> top level package", however since we have the split package problem we
> can't simply go with that.
>
> Still, we can respect the principles he recommends with a small
> variation. It's fair to assume that the `org.hibernate.search` prefix
> is "ours"; since the nature of the suggestion is focused on making
> sure there are no misunderstandings in the community about which names
> you can choose - as there is no central authority making sure module
> names aren't clashing - we should be fine within Hibernate projects
> with any `org.hibernate.X` prefix, as long as we coordinate and reach
> an agreement on this list.
>
> So, I propose we use:
>
> Engine module:
>  - org.hibernate.search.engine
>
> ORM integration module:
>  - org.hibernate.search.orm
>
> Those names sound good to me.


> JGroups, JMS backends:
>   [ no automatic module name ? Excepting some "guidelines" in the JMS
> module, these are not public API so nobody would benefit from it -
> also we think we might want to phase out the name "backend" in the
> future ]

Elasticsearch integration module [hibernate-search-elasticsearch.jar]:
>  - org.hibernate.search.elasticsearch
>
> Elasticsearch / AWS security integration:
>  [ no automatic module name: no public API ]
>
> Serialization / Avro
>  [ no automatic module name: no public API ]
>
> WDYT?
>

The user may still need to reference those modules when launching a
modularized application. Also if they don't directly declare say the JMS
backend as a dependence of their own module, they'd still have to specify
it via --add-modules, so to resolve these additional modules and add them
to the module graph. Hence I'd declare automatic module names for these,
too.


>
> We could also pick names for the ones which I've listed as "no public
> API" but I see no point: as we're only assigning an "Automatic Module
> Name" we won't be able to explicitly state that the other modules
> depend on these. So nobody will use them, and things are a bit in flux
> anyway in this area because of Hibernate Search 6 plans.
>

I don't fully understand this paragraph.

>
> Another optional altogether: since we have split packages which we'll
> have to resolve before we can actually transform these into fully
> fledged modules, I think an acceptable position is also to say we
> won't be publishing any automatic module name yet. Personally I'm
> inclined to go with the names suggested above, at least some others
> can start making baby steps, even if it's not all there.
>

IMO automatic module names should only be declared after at least some
basic vetting that these modules will actually work when used as modules.
If that's not the case, I wouldn't add these headers, as users rightfully
may consider their presence as endorsement of using them as modules.

That said, I can't seem to find split packages between engine and orm. In
fact I can launch an application with both of them on the module path just
fine. So there may be no problem actually?


> # What I don't like:
> For one, that the typical application will need to import both
> `org.hibernate.search.engine` and `org.hibernate.search.orm`, and
> likely more as well (e.g. Elasticsearch API, Lucene API module is
> coming, ..).
>

I'm not exactly sure what you mean by "import" here. But if it's about the
user having to declare dependences in their module descriptor to
o.h.s.engine and o.h.s.orm modules, you may consider to make the former a
transitive dependence of the latter once you add actual module descriptors:

    module org.hibernate.search.orm {
        requires transitive org.hibernate.search.engine;
        ...
    }

That way the user just has to add declare the dependence to o.h.s.orm.
That's definitely suitable if APIs in o.h.s.orm use types from engine in
their public API signatures.


> Maybe similar to BOM's today we could publish a module which
> statically imports multiple of these, that could be nicer to use but
> we risk needing to publish (and document) one for each of a selection
> of combinations. So let's not start with such things yet.
>
> Thanks,
> Sanne
>
> [1] http://blog.joda.org/2017/05/java-se-9-jpms-automatic-modules.html
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