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From "Matthew T. Adams (JIRA)" <j...@apache.org>
Subject [jira] [Created] (JDO-683) Allow version field/property to be visible to application
Date Fri, 26 Aug 2011 17:13:29 GMT
Allow version field/property to be visible to application
---------------------------------------------------------

                 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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