Jonathan,
Sorry to bicker but is "The only time that this would be benefical....would
be when you were assured that the primary key did exist in the database at
the time of transactional work" the same as "entities are well known and
stable...findByPrimaryKey("France")".
<note-to-jonathan>
stop bickering on this mailing list and back to working on our next release
</note-to-jonathan>
William
-----Original Message-----
From: A mailing list for Enterprise JavaBeans development
[mailto:[EMAIL PROTECTED]]On Behalf Of Jonathan Weedon
Sent: Wednesday, November 22, 2000 12:05 PM
To: [EMAIL PROTECTED]
Subject: Re: findByPrimaryKey spec. question
William Louth wrote:
>
> Option 'None'. OK. So you would not have any problems with a container
> returning a remote reference to an entity bean that does not exist in the
> database. Only when you call a business method on the remote will you
client
> detect the error. This will result in confusing client exception handling
> code. Would it not be easier to have already captured this exception and
> reported it prior to normal business method invocations. The only time
that
> this would be benefical (optimization i.e. no verification sql statement)
> would be when you were assured that the primary key did exist in the
> database at the time of transactional work. Unless the primary key was
> obtained in the same transaciton there really is no assurance since many
> transactions could be executing simulatenously in any number of processes
> both ejb and 'non-ejb' based.
William,
Sorry to bicker, but I think there are quite a few situations where having
the findByPrimaryKey method simply return an object reference without
attempting
to verify the existence of the object is useful. (That's why I added this
feature to our product.)
Consider two cases:
1) The entities are well known and stable. For example, if you have
entities
representing geographical locations, these tend to be fairly stable.
Therefore,
having your call to:
Country france = CountryHome.findByPrimaryKey("France");
not actually verify that Russia is a country is pretty reasonable IMO. Note
that
if for some reason France is no longer a country, then your first usage of
the
entity will throw an exception.
2) You have heavy concurrency. In this case, it is very possible that
between
your findByPrimaryKey and your use of the entity, that the entity be
removed.
Of course, if you are running against a database that provides true
serializability,
then this cannot happen, but:
a) The major databases have "trouble" providing true serialization, and
b) True serialization is computationally expensive, and probably not needed
in
many applications (which provides some rationale for (a)).
-jkw
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