On Castor's web site you can read about long transactions:
http://castor.exolab.org/long-transact.html
It says
"Since the time interval between the first and the second transaction is relatively
big, it is desirable to perform dirty checking, i.e. to check that the object has not
been modified in the database during the long transaction. For that the object must
hold a timestamp: it is set by Castor during the first Castor transaction and is
checked during the second one. In order to enable the dirty checking for long
transactions, the object should implement the interface
org.exolab.castor.jdo.TimeStampable having two methods:
long jdoGetTimeStamp()and
void jdoSetTimeStamp(long timeStamp)"
I don't quite get this: It doesn't say that you should put the timestamp on the
database, so how does it work? If someone else updates the db while I'm in a long
transaction, how should I be able to recognize this if I only check a timestamp set in
my local instance of the class???
The well-known timestamp check as I know it works if you put a timestamp on the
database, and it works like this:
1. read a record from the db, keep the data including the "last modified" timestamp
2. think.......
3. now we're ready to update the db:
4. read the record once more.
5. check if the current timestamp is the same as the one we read long a go.
6. if identical, update the record
7. if not identical tell the user that he has to redo his update (since someone else
updated the record while he was thinking......)
I'd also appreciate if anyone could tell me if I need to add anything to the mapping
file to make long transactions work.
Thanks a lot for any help......
/Keld
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