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Posted to dev@felix.apache.org by Stefan Seifert <ss...@pro-vision.de> on 2016/08/19 22:16:30 UTC
[Converter] Flexible Adpater Rule convert A to X and vice versa
we want to use the converter service as part of the sling context-aware configuration, and started with a first implementation. [1]
in sling we have a special form of map (a ValueMap) which supports additional features like typed access (with a resource provider-specific conversion magic under the hood), and support for nested maps. we want to map such valuemaps to annotation classes. this is working fine, but it does not use the special valuemap typed methods, and nested classes are not supported either because the child resources are not represented as nested maps in the valuemap.
what we need is a custom rule to provide some code to the converter how to handle the valuemap specifics. but neither the current converter implementation nor the API defined in [2] seems to support this currently.
what is supported are rules von converting class A to B and vice versa, but A and B have to be well-known. what we need is A to X and vice versa, where A is well-known, but X can by any class (e.g. any project-specific annotation class). details what we want to do described in [3].
is it planned to add such a more flexible rule to the specification (and implementation)? in the current implementation only one of the rule-related methods are implemented.
stefan
[1] https://svn.apache.org/repos/asf/sling/trunk/contrib/extensions/contextaware-config
[2] https://github.com/osgi/design/raw/master/rfcs/rfc0215/rfc-0215-object-conversion.pdf
[3] https://issues.apache.org/jira/browse/SLING-5982
RE: [Converter] Flexible Adpater Rule convert A to X and vice versa
Posted by Stefan Seifert <ss...@pro-vision.de>.
hello david.
thanks a lot for the quick prototype - that was exactly what i thought of.
unfortunately further experimenting with this enhanced functionality it still does not work fort solving the "nested configuration" usecase - i currently cannot think of an elegant way to bring it together with the converter concept, because always the underlying resource hierarchy is involved as well. see this comment [1] and svn ref [2] for details.
stefan
[1] https://issues.apache.org/jira/browse/SLING-5982?focusedCommentId=15433697#comment-15433697
[2] http://svn.apache.org/viewvc/sling/trunk/contrib/extensions/contextaware-config/impl/src/main/java/org/apache/sling/contextaware/config/impl/ConfigurationBuilderImpl.java?r1=1757438&r2=1757437&pathrev=1757438
>-----Original Message-----
>From: David Bosschaert [mailto:david.bosschaert@gmail.com]
>Sent: Tuesday, August 23, 2016 5:12 PM
>To: dev@felix.apache.org
>Subject: Re: [Converter] Flexible Adpater Rule convert A to X and vice
>versa
>
>Hi Stefan,
>
>I have prototyped more flexible adapter rules a little bit and committed
>the current state to the Converter codebase.
>
>The adapter now tries to find the most specific adaptation rule available
>for a given conversion, but it walks up the class hierarchy. So you could
>specify that you want to convert from ValueMap.class to Object.class where
>object will behave as a full wildcard.
>
>Then, if you use the Rule class [1] to specify the adapter rule, you
>receive a callback to the following functional interface method [2]:
> T convert(F obj, Type targetType)
>
>which gives you access to the target type that the object needs to be
>converted to. You can also return the special value CANNOT_CONVERT
>indicating that the adapter rule cannot handle a given conversion.
>
>You can see some examples in the following testWildcardAdapter() test case
>[3].
>
>Would this help you with your use-case?
>
>Best regards,
>
>David
>
>[1]
>https://svn.apache.org/viewvc/felix/trunk/converter/src/main/java/org/osgi/
>service/converter/Rule.java?view=markup
>[2]
>https://svn.apache.org/viewvc/felix/trunk/converter/src/main/java/org/osgi/
>service/converter/ConvertFunction.java?view=markup
>[3]
>https://svn.apache.org/viewvc/felix/trunk/converter/src/test/java/org/apach
>e/felix/converter/impl/AdapterTest.java?view=markup#l71
>
>
>On 22 August 2016 at 10:43, David Bosschaert <da...@gmail.com>
>wrote:
>
>> Hi Stefan,
>>
>> I see the use-case and in a different context I also came across a
>> use-case for 'wildcards' in the rules. I think this would be a good
>> feature. I'll try to prototype something for that over the coming few
>days
>> and ping back here once I have something to try out.
>>
>> Cheers,
>>
>> David
>>
>> On 19 August 2016 at 23:16, Stefan Seifert <ss...@pro-vision.de>
>wrote:
>>
>>> we want to use the converter service as part of the sling context-aware
>>> configuration, and started with a first implementation. [1]
>>>
>>> in sling we have a special form of map (a ValueMap) which supports
>>> additional features like typed access (with a resource provider-specific
>>> conversion magic under the hood), and support for nested maps. we want
>to
>>> map such valuemaps to annotation classes. this is working fine, but it
>does
>>> not use the special valuemap typed methods, and nested classes are not
>>> supported either because the child resources are not represented as
>nested
>>> maps in the valuemap.
>>>
>>> what we need is a custom rule to provide some code to the converter how
>>> to handle the valuemap specifics. but neither the current converter
>>> implementation nor the API defined in [2] seems to support this
>currently.
>>>
>>> what is supported are rules von converting class A to B and vice versa,
>>> but A and B have to be well-known. what we need is A to X and vice
>versa,
>>> where A is well-known, but X can by any class (e.g. any project-specific
>>> annotation class). details what we want to do described in [3].
>>>
>>> is it planned to add such a more flexible rule to the specification (and
>>> implementation)? in the current implementation only one of the rule-
>related
>>> methods are implemented.
>>>
>>> stefan
>>>
>>> [1] https://svn.apache.org/repos/asf/sling/trunk/contrib/extensi
>>> ons/contextaware-config
>>> [2] https://github.com/osgi/design/raw/master/rfcs/rfc0215/rfc-
>>> 0215-object-conversion.pdf
>>> [3] https://issues.apache.org/jira/browse/SLING-5982
>>>
>>>
>>>
>>
Re: [Converter] Flexible Adpater Rule convert A to X and vice versa
Posted by David Bosschaert <da...@gmail.com>.
Hi Stefan,
I have prototyped more flexible adapter rules a little bit and committed
the current state to the Converter codebase.
The adapter now tries to find the most specific adaptation rule available
for a given conversion, but it walks up the class hierarchy. So you could
specify that you want to convert from ValueMap.class to Object.class where
object will behave as a full wildcard.
Then, if you use the Rule class [1] to specify the adapter rule, you
receive a callback to the following functional interface method [2]:
T convert(F obj, Type targetType)
which gives you access to the target type that the object needs to be
converted to. You can also return the special value CANNOT_CONVERT
indicating that the adapter rule cannot handle a given conversion.
You can see some examples in the following testWildcardAdapter() test case
[3].
Would this help you with your use-case?
Best regards,
David
[1]
https://svn.apache.org/viewvc/felix/trunk/converter/src/main/java/org/osgi/service/converter/Rule.java?view=markup
[2]
https://svn.apache.org/viewvc/felix/trunk/converter/src/main/java/org/osgi/service/converter/ConvertFunction.java?view=markup
[3]
https://svn.apache.org/viewvc/felix/trunk/converter/src/test/java/org/apache/felix/converter/impl/AdapterTest.java?view=markup#l71
On 22 August 2016 at 10:43, David Bosschaert <da...@gmail.com>
wrote:
> Hi Stefan,
>
> I see the use-case and in a different context I also came across a
> use-case for 'wildcards' in the rules. I think this would be a good
> feature. I'll try to prototype something for that over the coming few days
> and ping back here once I have something to try out.
>
> Cheers,
>
> David
>
> On 19 August 2016 at 23:16, Stefan Seifert <ss...@pro-vision.de> wrote:
>
>> we want to use the converter service as part of the sling context-aware
>> configuration, and started with a first implementation. [1]
>>
>> in sling we have a special form of map (a ValueMap) which supports
>> additional features like typed access (with a resource provider-specific
>> conversion magic under the hood), and support for nested maps. we want to
>> map such valuemaps to annotation classes. this is working fine, but it does
>> not use the special valuemap typed methods, and nested classes are not
>> supported either because the child resources are not represented as nested
>> maps in the valuemap.
>>
>> what we need is a custom rule to provide some code to the converter how
>> to handle the valuemap specifics. but neither the current converter
>> implementation nor the API defined in [2] seems to support this currently.
>>
>> what is supported are rules von converting class A to B and vice versa,
>> but A and B have to be well-known. what we need is A to X and vice versa,
>> where A is well-known, but X can by any class (e.g. any project-specific
>> annotation class). details what we want to do described in [3].
>>
>> is it planned to add such a more flexible rule to the specification (and
>> implementation)? in the current implementation only one of the rule-related
>> methods are implemented.
>>
>> stefan
>>
>> [1] https://svn.apache.org/repos/asf/sling/trunk/contrib/extensi
>> ons/contextaware-config
>> [2] https://github.com/osgi/design/raw/master/rfcs/rfc0215/rfc-
>> 0215-object-conversion.pdf
>> [3] https://issues.apache.org/jira/browse/SLING-5982
>>
>>
>>
>
Re: [Converter] Flexible Adpater Rule convert A to X and vice versa
Posted by David Bosschaert <da...@gmail.com>.
Hi Stefan,
I see the use-case and in a different context I also came across a use-case
for 'wildcards' in the rules. I think this would be a good feature. I'll
try to prototype something for that over the coming few days and ping back
here once I have something to try out.
Cheers,
David
On 19 August 2016 at 23:16, Stefan Seifert <ss...@pro-vision.de> wrote:
> we want to use the converter service as part of the sling context-aware
> configuration, and started with a first implementation. [1]
>
> in sling we have a special form of map (a ValueMap) which supports
> additional features like typed access (with a resource provider-specific
> conversion magic under the hood), and support for nested maps. we want to
> map such valuemaps to annotation classes. this is working fine, but it does
> not use the special valuemap typed methods, and nested classes are not
> supported either because the child resources are not represented as nested
> maps in the valuemap.
>
> what we need is a custom rule to provide some code to the converter how to
> handle the valuemap specifics. but neither the current converter
> implementation nor the API defined in [2] seems to support this currently.
>
> what is supported are rules von converting class A to B and vice versa,
> but A and B have to be well-known. what we need is A to X and vice versa,
> where A is well-known, but X can by any class (e.g. any project-specific
> annotation class). details what we want to do described in [3].
>
> is it planned to add such a more flexible rule to the specification (and
> implementation)? in the current implementation only one of the rule-related
> methods are implemented.
>
> stefan
>
> [1] https://svn.apache.org/repos/asf/sling/trunk/contrib/
> extensions/contextaware-config
> [2] https://github.com/osgi/design/raw/master/rfcs/
> rfc0215/rfc-0215-object-conversion.pdf
> [3] https://issues.apache.org/jira/browse/SLING-5982
>
>
>