[jboss-as7-dev] JBoss Modules: can I dynamically add dependency?

[ssilvert at redhat.com]

On 9/24/2012 12:18 PM, Jason Greene wrote:
> There are two solutions to this problem.
>
> 1) Switch the interaction to use plugable constructs (common SPI (interfaces & superclasses), dynamically loaded implementation which depends on the common SPI)
Unfortunately, we don't control that part.  It's defined by the JSF impl.
>
> 2) Dynamically generate a module with an extra resource root to the same jar
That's what I wanted to do, but David says dynamic generation of modules
is not possible given our performance constraints.

The only other thing I can think of is to have a tool that installs and
configures the modules for you.  Then the user or admin wouldn't have to
do it by hand.  But such a tool would get rather complex in a domain
configuration.

>
>
> On Sep 24, 2012, at 10:29 AM, ssilvert at redhat.com wrote:
>
>> OK.  Thanks.
>>
>> This is alright for now because we only have two JSF impls.  But we want
>> to allow users to install additional impls.  So it's a little ugly to
>> tell them that they have to make another copy of the jsf-injection
>> module for each one.
>>
>>
>> On 9/24/2012 9:47 AM, David M. Lloyd wrote:
>>> On 09/24/2012 07:49 AM, ssilvert at redhat.com wrote:
>>>> On 9/24/2012 8:15 AM, David M. Lloyd wrote:
>>>>> Unfortunately this premise is flawed from the start: if you had two
>>>>> apps, each requiring a different JSF implementation, this idea could
>>>>> never work.
>>>> I'm not sure what you mean here.  This is already working.
>>>>> In any case you cannot change the dependencies of a static module at
>>>>> runtime.  Normally when multiple implementations are available you would
>>>>> use reflection to instantiate the implementation you need.  If this is
>>>>> not possible then you'll need a separate module for each implementation
>>>>> type.
>>>> That's the problem.  It's not that I need to instantiate something.
>>>> Rather, I need to put jsf-injection in a position where the JSF impl
>>>> will find my service and instantiate it.   So the way things are now I
>>>> have to statically define a new jsf-injection module for each JSF impl.
>>>> Those modules are exactly the same except for one dependency declaration.
>>> If JSF is instantiating your module via SPI or similar then yes, you 
>>> will need to clone your classes for each implementation because you're 
>>> statically linking to the Mojarra API (meaning at run time your modules 
>>> are no longer exactly the same as classes have different supertypes and 
>>> so on).
>>>
>>>> If I could programatically define the module then I wouldn't have to
>>>> repeat myself.
>>>>
>>>> Maybe JBoss Modules was never meant to be used that way?
>>> If every Mojarra implementation is statically defined as a module, then 
>>> you will have to create separate static modules for each one.  If you're 
>>> loading them in from a deployment then you should use the deployers' API 
>>> for defining module dependencies to automatically tack on a copy of your 
>>> integration classes.
>>>
>>> The reason this is so is that in order to have the very fast startup we 
>>> have today, the initial module loader runs in a purely static environment.
>>>
>>>>> On 09/24/2012 07:06 AM, ssilvert at redhat.com wrote:
>>>>>> I have a module defined like this (currently in master with main and
>>>>>> slot="1.2):
>>>>>> <module xmlns="urn:jboss:module:1.1" name="org.jboss.as.jsf-injection">
>>>>>>      <resources>
>>>>>>          <resource-root
>>>>>> path="jboss-as-jsf-injection-7.2.0.Alpha1-SNAPSHOT.jar"/>
>>>>>>      </resources>
>>>>>>
>>>>>>      <dependencies>
>>>>>>          <module name="com.sun.jsf-impl"/>   <----- this needs to be dynamic
>>>>>>          <module name="javax.api"/>
>>>>>>          <module name="org.jboss.as.web"/>
>>>>>>          <module name="javax.servlet.api"/>
>>>>>>      </dependencies>
>>>>>> </module>
>>>>>>
>>>>>> Inside a DeploymentUnitProcessor, the module above is added to the
>>>>>> ModuleSpecification along with the module for the selected JSF
>>>>>> implementation.  The problem I have is that the JSF Injection code is
>>>>>> the same for any Mojarra implementation.  But to support multiple
>>>>>> implementations I need to declare a separate jsf-injection module with a
>>>>>> hard-coded dependency on each implementation installed.
>>>>>>
>>>>>> If I could create a module dynamically and dynamically add its
>>>>>> dependencies then there would be no need to create more and more modules
>>>>>> containing the same jsf-injection jar.
>>>>>>
>>>>>> I've been looking at the JBoss Modules API and I don't see how to do
>>>>>> this.  Is it possible?
>>>>>>
>>>>>> Stan
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