The wrong design is using db constraint to manage rules which should be located in the business tier. That's to say not coding a rule because you know that a constraint has been set within the db.
But coding a business tier which is able to manage all rules without using constraint seems to be difficult and i don't know if following this theorical principle is possible. Especially in a multithreading environment.
I guess that if i have problem to check the unicity of a field, i will have some problems in coding more complex rules.
What is your mind about that? How do you check that something is unique?
Jean-Philippe
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[EMAIL PROTECTED] wrote:
Hi, Whatever you do at the other tiers, I wouldn't call defining a PK a wrong design. That is ENFORCING a rule, it does not mean you have to let the DB handle the detection of a duplicated value, it just means that the DB won't allow you to introduce a duplicate value, in case you have bug or something similar, not unlikely to happen at the beginning in multithreaded environments. Another advantage is that if someday you introduce data in your DB through another tier, like a batch job with a bunch of SQL commands or a native application, the contraint is still enforced. IMHO, unless you put a lot of access restrictions on your DB, if you check all of that only at the upper tiers you cannot guarantee the data is consistent at the DB. Just my 2ec, D.Yes, but my name is no defined as a PK and i don't want to use unicity constraint (in fact i don't know if the default jboss database manages it, the @pk-constaint tag has no effect. Moreover, if your name is defined as a PK, you don't need any more to check the unicity and you have a wrong design with some rules managed by the db tier. At least, i've been said that the ejb server can delay the call to ejbstore. In this case you get your exception after the call (at the end of the transaction i guess) of the create function which can be difficult to manage.-- This message was sent using Sake Mail, a web-based email tool from Endymion Corporation. http://www.endymion.com/products/sake
Yes, but my name is no defined as a PK and i don't want to use unicity constraint (in fact i don't know if the default jboss database manages it, the @pk-constaint tag has no effect.
Moreover, if your name is defined as a PK, you don't need any more to check the unicity and you have a wrong design with some rules managed by the db tier.
At least, i've been said that the ejb server can delay the call to ejbstore. In this case you get your ?exception after the call (at the end of the transaction i guess) of the create function which can be difficult to manage.
[EMAIL PROTECTED] wrote:
If the name is defined as a PK I think you shouldn't have any problem... On Tue, 2003-07-29 at 03:46, Jean-philippe VIGNIEL wrote:What appens if two persons create the same object at the same time. With the default transaction mode, i think (but i can be wrong) that the object can be created twice. By example; User1: select * from object where name="bob"->nothing so it's ok User2: select * from object where name="bob"->nothing so it's ok User1: create "bob" User2: create "bob" User1: close transaction User2: Close transaction And there are two bob objects within the database. Before EJB tomanage this case we did a select for update. Perhaps it's possible to set the transaction mode to serialized for the create method??? Thanks for your advice about with subject?
