[ http://issues.apache.org/jira/browse/JDO-204?page=comments#action_12357824 ]
Craig Russell commented on JDO-204: ----------------------------------- I understand that some implementations have the ability to store completely different classes in a persistent field. But there is currently no standard way to describe how this is done. For example, in JDO1 TCK we had a field of Object and stored String and Long in the field in different instances. And if you serialize the contents of the field, there is no issue. But now we allow the user to specify the mapping for embedded and referenced storage. And there is no standard way for the user to tell the implementation how to store these. You would at least need some discriminator column to store the class of the instance. Without having a standard way to describe the storage of heterogeneous instances, I'm reluctant to go too far in standardizing the classes that can be stored in the field. But this is different from the proposal, which is to allow overriding of the compiled field type at deployment time, for example to specify that even though the object model says that there is an Object stored in a field, the only class that can be stored there is a SimpleClass. That said, I don't object to using the field-type to name a list of classes that can be stored, and using the <extension> metadata to describe in more detail how the storage is to be done. > Need attribute on field element for type > ---------------------------------------- > > Key: JDO-204 > URL: http://issues.apache.org/jira/browse/JDO-204 > Project: JDO > Type: Bug > Components: api20 > Reporter: Michelle Caisse > Assignee: Craig Russell > > Need to supply instantiated type information for Object & Interface fields. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira
