[jpa-spec users] [jsr338-experts] Re: updated spec draft (converters)

From: michael keith <>
Date: Wed, 14 Mar 2012 15:09:31 -0400

That would certainly be consistent.
Not as convenient, but definitely consistent :-)

Another approach would be to go back to defining the annotation on an
entity (i.e. like named queries, id generators and many other global
things that we already define) and point to the converter class.


@Converter(class=MyConverter.class autoApply=true)
public class Employee { ... }

On 14/03/2012 2:36 PM, Linda DeMichiel wrote:
> Currently @Converter has only one attribute, autoApply, although
> we have open issues around scoping (extending to subclasses, etc).
> It occurs to me that we could approach autoApply converters as we
> do default entity listeners, and require them to be listed in the
> orm.xml. If we did this, we could dispense with the @Converter
> annotation until such time as we needed it to further refine the
> semantics.
> Opinions? Fire away :-)
> -Linda
> On 3/14/2012 10:37 AM, Gordon Yorke wrote:
>> On 14/03/2012 1:49 PM, michael keith wrote:
>>> On 14/03/2012 12:18 PM, Gordon Yorke wrote:
>>>> On 14/03/2012 1:11 PM, michael keith wrote:
>>>>>>>>>> I've uploaded a draft of the spec with the attribute
>>>>>>>>>> converter additions to the document
>>>>>>>>>> downloads area,
>>>>>>>>>> The converter changes can be found in sections 3.7, 10.5, and
>>>>>>>>>> 11.1.10-11.
>>>>>>>>>> The following open issues are pending:
>>>>>>>>>> * Conversion of @Id and @Version.
>>>>>>>>>> * Explicit listing of converters in persistence.xml file. I'm
>>>>>>>>>> not sure I understand what
>>>>>>>>>> was being proposed here.
>>>>>>>>> When the archive is not scanned (it's an option in
>>>>>>>>> persistence.xml), the provider has no way of finding the list
>>>>>>>>> of converters unless the user explicitly list them in
>>>>>>>>> persistence.xml like it does list classes.
>>>>>>>> OK, thanks -- so would you propose that they simply be listed
>>>>>>>> using the class element?
>>>>>>> These are O/R mapping classes. Why would they be listed in
>>>>>>> persistence.xml? The flag to not scan for annotations
>>>>>>> (the xml-mapping-metadata-complete option) is in the orm.xml
>>>>>>> mapping file, that is where I would expect to specify
>>>>>>> these when not using annotations, right?
>>>>>> but the flag that controls scanning for persistence related
>>>>>> classes is in the persistence.xml file as is the list
>>>>>> of persistence related classes. By default the provider is not
>>>>>> allowed to scan for classes. Many deployments occur
>>>>>> without any orm.xml.
>>>>> There is an exclude-unlisted-classes setting in the
>>>>> persistence.xml file that *disables* scanning for entities,
>>>>> embeddables and mapped superclasses, but by default the provider
>>>>> is supposed to scan (when running in a container -
>>>>> outside the container it is not defined). This option was only
>>>>> added to enable a persistence unit to disable some
>>>>> classes from being considered even though they were in the same JAR.
>>>>> In any case, my point was that this is an object-relational
>>>>> mapping class and by design we have always tried to keep
>>>>> the O/R mapping concepts in the orm.xml file (when we are talking
>>>>> about not relying upon the annotation sensing,
>>>>> which I believe was the point).
>>>> exclude-unlisted-classes is true by default
>>> No, by default it is false (but I hope that is what you mean?)
>> No, the default is true : "<xsd:element
>> name="exclude-unlisted-classes" type="xsd:boolean" default="true"
>> minOccurs="0">" and portable Java SE applications must list all
>> managed persistence classes (section .
>>>> and so by default scanning by the provider must be *enabled*.
>>> Correct.
>>>> The scanning the container performs is defined elsewhere.
>>> We're not talking about container scanning, just provider scanning.
>>>> The only thing being discussed here is the auto scanning and how
>>>> the provider should be notified of the converter
>>>> classes when scanning is not enabled.
>>> Yes. So far you have mostly just restated what I said above, so
>>> we're good up to this point :-)
>> No, we disagree on whether @Converter classes will always be
>> discovered. Emmanuel's point and my point is that by
>> default in Java SE there is no way for a provider to find the
>> *annotated* auto-apply Converter classes. Users should
>> have the option of listing the annotated Converter classes within the
>> list of managed classes in the persistence.xml file.
>>>> Requiring an orm.xml file just to list the converter classes seems
>>>> out of place.
>>> Putting mapping information in our mapping file is exactly the right
>>> place, and is the way we designed it from the
>>> beginning. Listing them in with the entities/embeddables and mapped
>>> superclasses is clearly more convenient, but not
>>> architecturally the correct place for them to be.
>> I do not believe anyone is proposing listing converter classes within
>> other managed classes (ie .entities/embeddables
>> and mapped superclasses). That seems out of place to me.
>>> I guess we need to decide whether we want to go with architectural
>>> consistency or convenience. Both have merits and
>>> are valid arguments.
>> If it is architecturally inconsistent then why have the list of
>> annotated managed classes at all in the persistence.xml
>> file ? There is nothing inconsistent about continuing a configuration
>> pattern that is already defined in the specification.
>> For clarity, an element for converters should still be added to the
>> persistence-unit element in orm.xml for un-annotated
>> classes but I assumed that would be added later when the xsds are
>> updated.