Re: Feature proposal for JDO 2.1 maintenance: current DB time

[Craig L Russell]

Hi Christiaan,

On Dec 22, 2006, at 5:17 AM, Christiaan des Bouvrie wrote:

Hi,

I just want to add my vote for such a feature. I currently use direct
sql in order to deal with the server date, so a JDO solution would be
nice.



Based on the previous discussions, my suggestions:

-          In order to avoid confusion why not stress more that the
server date is returned: serverDate();

-          I would prefer if it is accessible through a method call. I
have some doubt however whether JDOHelper is the right place, since
currently JDOHelper has methods for state interrogation of persistent

the datastore). To me it would make more sense to add it to
PersistenceManager. This is basically also the difference in
JDOHelper.getObjectID() and PersistenceManager.getObjectByID();

objects (from a user point of view this does not require a connection to

I think you are right. It belongs not in a JDOHelper but associated with the back end server, which means either the PersistenceManagerFactory or PersistenceManager. Since there is a requirement that you get the result from the back end, which means that you need to have a connection to it, the PersistenceManager would seem to be the right interface to use.

type is already supported by JDO.

- I think serverDate() should return java.util.Date since this

There are a lot of types that might make sense. The reason I don't like Date is that there is not a good representation of the time zone. There is some crosstalk between Date and Calendar but getting the server's time zone is problematic.

I think introducing serverTimeStamp()
could cause confusion since that would introduce dependency on the
java.sql.TimeStamp class, making JDO less datastore / sql independent.

Yes, I agree that Timestamp isn't ideal either.

I think that Calendar solves both of these problems. Something like java.util.Calendar PersistenceManager.getServerCalendar() would do it. The Calendar includes time zone, locale, and Date all wrapped up together. You can get a TimeZone by asking getTimeZone() and get the Date with getTime().

To do it similar like the System class, why not introduce
PersistenceManager.serverNanoTime()  which translates the datastore
TimeStamp to nano seconds;

-          It would be nice to use the serverDate() method in JDOQL as
well, though for me retrieving the server Date and using that instance
in JDOQL to perform queries would suffice as well;

Craig

I was thinking that this would not quite be sufficient for e.g. finding Employees whose hire date was within two days. I think that SQL supports this functionality but JDOQL does not.

Kind regards,

Christiaan

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

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