Allow version field/property to be visible to application
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Key: JDO-683
URL: https://issues.apache.org/jira/browse/JDO-683
Project: JDO
Issue Type: Improvement
Components: api
Affects Versions: JDO 3 maintenance release 1
Reporter: Matthew T. Adams
Currently, it requires a vendor extension to make the version attribute (field
or property) of a PC visible to the application. Some knowledgeable
applications may need not only read access to the version field, but also write
access to it.
I propose that we allow version metadata to specify that a version attribute be
application-visible. For annotation-based metadata, I recommend that it be
allowed to be placed on fields & methods. For XML metadata, add XML attributes
"attribute-name" to the "version" element that allows the user to specify which
field or property is to hold the application-visible version value.
Along with this change would be verbiage in the spec noting that applications
really shouldn't change this value, but a knowledgeable application may change
it, based on a new PMF & PM property called something like
"javax.jdo.option.OnVersionChangeByApplication" with the following specified
values.
THROW: (default) the implementation will throw JDOUserVersionChangeException
(extends JDOUserException) as early as the time the value is set, at the next
flush, or at commit.
IGNORE: the implementation ignores the value the user set for the object's
version
ALLOW: the implementation allows and uses the value the user set for the
object's version
This allows users to who know how their implementation behaves on user-modified
version values to take advantage of such behavior.
All names proposed are up for discussion.
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