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

Sanne Grinovero sanne at hibernate.org
Mon Feb 12 13:28:07 EST 2018

On 12 February 2018 at 18:00, Gunnar Morling <gunnar at hibernate.org> wrote:
> 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.

Good point, I had not thought that our modules wouldn't be able to
load other extensions from classpath.

>> 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.

You mostly invalidated it with the previous comment, but what I meant
is that we can't have the `org.hibernate.search.engine` declare a
dependency on any implementation module, as we're not adding a
module-info definition.

>> 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?

Interesting, I'm pretty sure we had some. We had several issues
resolved over time to resolve them, I never realized we might have
completed them all. The "line" defining what belongs where is still
blurry though, we should make sure this won't have future regressions.

I'll see if we can produce fully fledged module-info descriptors then :)

>> # 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.

+1 that's the better option.

My thought was about automatic module names though, but totally
irrelevant if we go for full modules.


>> 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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