Bridging the world of namespace-aware XML and not namespace-aware object models
like Java, where an object can only have one field (attribute) with the same
name,
is quite difficult. In other words if we allow for multiple namespaces for XML
attributes (which at the moment is the case according to the spec) then we must
also adopt
that concept of namespaces in the Java object model.
And as a note, (namespace) prefixes by them self are meaningless. They only
convey meaning if they are associated with a namespace.
So we need a solution which is namespace-aware and not limited to, but
compatible to XML. In the light of this I suggest the
following interface, where "namespace" is now a generic concept (abstraction)
and does not necessarily stand for XML-namespaces per se.
public interface ExtraAttributes {
/**
* List the names of extra attributes for a given namespace.
*
* @param namespace the namespace for which to retrieve the names of
available attribute.
*
* @return an {@link Iterator} producing the {@link String}s of the
extra attribute names.
* for the given namespace.
*/
public Iterator<String> getExtraAttributeNames(String namespace);
/**
* Retrieve the value of an extra attribute.
*
* @param namespace the namespace from which to retrieve the attribute
value.
* @param name name of the extra attribute, whose value should be
retrieved.
* @return the value of the extra attribute or <code>null</code> if no
attribute with
* that name exists.
*/
public String getExtraAttributeValue(String namespace, String name);
}
What do you think.
Regards
Alex
--
finnova AG Bankware
Alexander Berger
Software Architect
Merkurstrasse 6
CH-5600 Lenzburg
Tel: +41 (0)62 886 48 07 (direkt)
Tel: +41 (0)62 886 47 47 (zentrale)
Fax: +41 (0)62 886 48 88
mailto:alexander.ber...@finnova.ch
http://www.finnova.ch
-----Ursprüngliche Nachricht-----
Von: Felix Meschberger [mailto:fmesc...@adobe.com]
Gesendet: Montag, 14. Januar 2013 10:39
An: dev@felix.apache.org
Betreff: Re: Metatype Service - OptionalAttributes - extra XML attributes with
namespace support
Hi
QNAme is an XML-ism and the API is XML-free (as I said, use of XML is just one
way to back the API). So I am extremely reluctant to using QName (regardless of
whether we use javax.xml.QName or define our own QName class). Always consider
the case where an QbjectClassDefinition might be backed by a MetaTypeProvider
service and not XML.
As for the interface (except QName question), I am fine.
However, I could assume we could have the name, if it comes from XML, to be
something like
{url}localname
or
prefix:localname
And, of course, the {url} or prefix: prefix would be omitted for the default
namespace (empty string) or the namespace of the metatype descriptor.
Regards
Felix
Am 14.01.2013 um 07:43 schrieb <alexander.ber...@finnova.ch>
<alexander.ber...@finnova.ch>:
> O.K. I see.
>
> Then I would suggest to add something like the following interface to
> AttributeDefinition and ObjectClassDefinition:
>
> public interface ExtraAttributes {
>
> /**
> * List the {@link QName}s of extra XML attributes.
> *
> * @return an {@link Iterator} producing the {@link QName}s of the
> extra attributes.
> */
> public Iterator<QName> getExtraAttributeNames();
>
> /**
> * Retrieve the value of an extra XML attribute.
> *
> * @param name {@link QName} of the extra attribute, whose value should
> be retrieved.
> * @return the value of the extra attribute or <code>null</code> if no
> attribute with
> * that name exists.
> */
> public String getExtraAttributeValue(QName name); }
>
> However, my initial question about QName and XML API support arises
> again as we are using QName here. Note, using just a String as
> argument to getExtraAttributeValue will not work, as several
> attributes with the same name but different Namespaces (prefixes) might exist
> on the same Element.
>
> Regards
> Alex
>
> --
> finnova AG Bankware
> Alexander Berger
> Software Architect
> Merkurstrasse 6
> CH-5600 Lenzburg
> Tel: +41 (0)62 886 48 07 (direkt)
> Tel: +41 (0)62 886 47 47 (zentrale)
> Fax: +41 (0)62 886 48 88
> mailto:alexander.ber...@finnova.ch
> http://www.finnova.ch
>
> -----Ursprüngliche Nachricht-----
> Von: Felix Meschberger [mailto:fmesc...@adobe.com]
> Gesendet: Samstag, 12. Januar 2013 22:15
> An: dev@felix.apache.org
> Betreff: Re: Metatype Service - OptionalAttributes - extra XML
> attributes with namespace support
>
>
> Am 10.01.2013 um 17:14 schrieb <alexander.ber...@finnova.ch>
> <alexander.ber...@finnova.ch>:
>
>> That's a good question.
>>
>> I think in terms of an API for accessing extra XML attributes,
>> chances are good that such an API could be standardized (at least
>> technically). But in terms of the specific "extra XML attributes" I
>> see no way to get them standardized. And I guess that is the reason
>> why the XSD (XML Schema) for the metatype descriptions allows for extra
>> attributes (which reside in another XML namespace). Maybe someone that has
>> worked on the specification might clarify what the intention about allowing
>> the extra attributes was.
>
> Originally the idea was, that the same XML files would be used for metatype
> descriptors and other applications. Which is why it is lenient to other data.
>
>>
>> Unless I know more about the matter I long for the following:
>>
>> 1. Anybody can enrich the metatype descriptions with his own
>> (specific/individual) metadata.
>> The current specification supports this by allowing extra XML attributes
>> that reside in another namespace (##other).
>>
>> 2. An API to list respectively retrieve those extra attributes. And ideally
>> such an API could become part of the
>> metatype specification (new methods on the already existing interfaces or
>> on new sub-interfaces).
>
> Please also consider that XML files are only one source for metatype
> descriptors. Access is always through API which can also be implemented
> without having XML.
>
> One option I could conceive, though, would be that we extend the
> AttributeDefinition interface with a new method:
>
> String getExtraAttribute(String name);
>
> which returns the named attribute.
>
> WDYT ?
>
> Regards
> Felix
>
>
>>
>> Regards
>> Alex
>>
>>
>> -----Ursprüngliche Nachricht-----
>> Von: Felix Meschberger [mailto:fmesc...@adobe.com]
>> Gesendet: Donnerstag, 10. Januar 2013 15:58
>> An: dev@felix.apache.org
>> Betreff: Re: Metatype Service - OptionalAttributes - extra XML
>> attributes with namespace support
>>
>> Hi Alex,
>>
>> Sorry, I missed your message from last week.
>>
>> Am 10.01.2013 um 13:34 schrieb <alexander.ber...@finnova.ch>
>> <alexander.ber...@finnova.ch>:
>>
>>> I want to add some extra attributes to the metadata (XML) which will then
>>> be used by a (special) administration console which knows about that extra
>>> attributes. These extra attributes will be used to allow a more concise
>>> representation of Configurations in the Graphical User Interface (GUI). For
>>> example to show a value from a certain configuration property instead of
>>> its PID in the GUI, as PIDs are quite meaningless to the average User.
>>
>> Thanks. The reason for asking is, whether your use case is in fact something
>> that could be generalized to properly enhance the API. And thus to try to
>> get it into the specification.
>>
>> Do you think such a generalization might be possible ?
>>
>> Regards
>> Felix
>>
>>>
>>> Regards
>>> Alex
>>>
>>> --
>>> finnova AG Bankware
>>> Alexander Berger
>>> Interface Development
>>> Merkurstrasse 6
>>> CH-5600 Lenzburg
>>> Tel: +41 (0)62 886 48 07 (direkt)
>>> Tel: +41 (0)62 886 47 47 (zentrale)
>>> Fax: +41 (0)62 886 48 88
>>> mailto:alexander.ber...@finnova.ch
>>> http://www.finnova.ch
>>>
>>> -----Ursprüngliche Nachricht-----
>>> Von: Felix Meschberger [mailto:fmesc...@adobe.com]
>>> Gesendet: Freitag, 4. Januar 2013 14:41
>>> An: dev@felix.apache.org
>>> Betreff: Re: Metatype Service - OptionalAttributes - extra XML
>>> attributes with namespace support
>>>
>>> Hi,
>>>
>>> Am 04.01.2013 um 08:23 schrieb <alexander.ber...@finnova.ch>
>>> <alexander.ber...@finnova.ch>:
>>>
>>>> Hi
>>>>
>>>> I intend to use extra (optional) XML attributes with the Metatype Service.
>>>
>>> Before commenting in detail, I would be interested to know what exactly you
>>> want to achieve by using additional attributes on object class and
>>> attribute definitions.
>>>
>>> Regards
>>> Felix
>>>
>>>
>>>> For this purpose I examined the
>>>> Felix metatype service implementation and found the class
>>>> org.apache.felix.metatype.OptionalAttributes,
>>>> which is extended by AD, OCD, ... . But unluckily this class is
>>>> neither inherited by LocalizedObjectClassDefinition nor by
>>>> LocalizedAttributeDefinition, which makes it quite useless for the moment.
>>>>
>>>> Another Problem is that OptionalAttributes does not support XML namespaces
>>>> for the attribute names.
>>>> The underlying Map should use something like
>>>> javax.xml.namespace.QName as key and not just the name of the
>>>> attribute (String). Note, XML namespace support is crucial as extra XML
>>>> attribute have to be in a different (##other) namespace (see "Metatype
>>>> Service Specifiaction" (Version 1.2), section 105.9 "XML Schema").
>>>>
>>>> The above observations lead me to the following question:
>>>>
>>>> 1. Is it still a requirement for Felix subprojects to avoid
>>>> dependencies on packages like java.xml.** and rely on kxml2 instead?
>>>> a. If so, then I could try create a patch for metatype service which
>>>> will add support for extra XML attributes (including XML namespace support
>>>> but not using javax.xml.namespace.QName),
>>>> so that extra XML attributes could be retrieved from AD, OCD, ...,
>>>> LocalizedObjectClassDefinition and LocalizedAttributeDefinition instances.
>>>> b. If not, then I could try to create a similar patch as described
>>>> above (a) but using javax.xml.namespace.QName instead.
>>>>
>>>> Note, the class javax.xml.namespace.QName is part of JavaSE since version
>>>> 1.5 older versions as well as JavaME do not contain that class.
>>>>
>>>> Alex
>>>>
>>>>
>>>
>>
>
