Santiago Gala wrote:
<snip>
>
> What I'm doing is:
>
> Create a findGreatestId() method for each CMP bean. the where clause would be
> something like:
>
> WHERE id = (SELECT max(id) FROM table)
>
> Call it inside the ejbCreate method to get the biggest used id, increment it and
> assign it before returning. Warning: it will raise and exception, that must be
> caught, if the table is empty. In this case, set id to 1.
>
> It should work well, it is completely portable and it uses all the connection
> pooling and similar characteristics in Jonas.
>
> It is not very elegant, but we have seen no problems using it. If you require
> permanent unique ids, and you are removing objects, it is not for you, as the same
> id can be reused if the last object is created and then removed.
Are you sure this is thread safe? What if two threads tries to create a
new bean, and
the server is switching out one for the other while the first sent the
sql to get the
current max, while not yet incremented the number.
In a busy environment, these things happen every so often. On a perl
system a friend
was working on, new users got someone elses account number about twice a
week.
<snip>
Regards,
Anders Bolager
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