[jboss-as7-dev] jax-rs deployments have incomplete module imports

[Jason Greene]

On Sep 12, 2012, at 2:52 PM, "David M. Lloyd" <david.lloyd at redhat.com> wrote:

> On 09/12/2012 02:37 PM, Bill Burke wrote:
>> 
>> 
>> On 9/12/2012 2:39 PM, Jason Greene wrote:
>>> 
>>> On Sep 12, 2012, at 1:13 PM, Bill Burke <bburke at redhat.com> wrote:
>>> 
>>>> I'm sending this here before I submit a JIRA.
>>>> 
>>>> JAX-RS deployments need to import more dependencies, specifically:
>>>> 
>>>> * the jackson libraries
>>>> * Apache Http Client 4 libraries
>>>> 
>>>> Jackson and HC4 are often used within jax-rs deployments because users
>>>> need to add additional configuration and initialization that can only be
>>>> done programmatically.
>>> 
>>> OK but are you sure you want to support direct usage of those libraries? Part of the reason why we don't re-export third party libs we use is because we want the flexibility to upgrade/drop/replace, and we don't want to support a user using say google collections, just because we made use of it in our code base.
>>> 
>>> (In case it sounds that way, I'm not arguing against you, I am just legitimately asking if you want to worry about maintenance of those items. If so no problem)
>> 
>> Yes, we have to expose and support direct usage.  They are both
>> intricate in developing JAX-RS applications.  Resteasy client framework
>> is just a layer on top of Apache HC.  For example, we rely on HC4 APIs
>> to set up user/password and other authentication settings.  Jackson
>> annotations are used a lot as well as creating
>> ObjectMapper's(JAXBContext equivalent) directly that are plugged in
>> through JAX-RS apis (ContextResolver).
>> 
>> I want to really apologize for not checking up on this months and months
>> ago.  I incorrectly assumed that things would just work and be exposed
>> as they were in AS6.  A lot of this is related to my lack of
>> understanding of the module system too.
>> 
>>>> 
>>>> Another thing:
>>>> 
>>>> Can modules be declared with empty <resources>?  It would be cool if we
>>>> could have a resteasy module with which all it did was define what
>>>> modules it would export to a deployment.  Right now this metadata is
>>>> hardcoded, correct?  This sucks for multiple reasons.  One: users will
>>>> have to manually define a lot of module dependencies, or they will end
>>>> up including resteasy and thirdparty libraries that may conflict and
>>>> cause CCEs.  Two:  Its very hard for me to provide a patch to AS7 if I
>>>> want to provide *ALL* features that come with the resteasy distribution.
>>>>   Sure I could include and export everything within the current resteasy
>>>> default module, but I would rather have separate modules for these features.
>>> 
>>> Sure we do that for javaee for example (aggregation modules). If you would like to make an aggregate for JAX-RS thats fine, the only problem is you will prevent people from being able to exclude anything in that list. So to use an example if you add apache http client 4.1, and a user decides they want 3.0 or 5.0, they would have to exclude the aggregate module, and then include everything in it except http client. You could also do various different common combinations.
>> 
>> I just don't see a way around it.  Couldn't they also just modify the
>> aggregation module?  Maybe you need to add a feature to JBoss Modules
>> that allows a deployment to override the version of an exported dependency?
> 
> No, overriding won't work.  In this case I think the best approach is to 
> include these constituent APIs in with the aggregate and pull it in to 
> the deployment when they use JAX-RS.  If JAX-RS uses a specific HC 
> version then the user simply doesn't have the option of using any other 
> version when using JAX-RS - there's no getting around that.  But it 
> might be good to only import these libraries into the deployment if 
> they're actually using JAX-RS.

I just realized they could class filter the import though which would solve it. They can also take advantage of ordering.