How does JForum make sure there will be no two users with same name inserted into the database?

[adam cooper]

I'm reading the source code of JForum v2.x.x from http://jforum.net/.

I see that in the class UserAction, there is a call to dao.isUsernameRegistered(username) to check the name first before inserting a new user into the table. But, as far as I know, JForum runs in a multithread environment. What if when two different threads check if there is such a user with the name, say 'adam', in the table at the same time, and they both get false as the answer, and then they both insert a new user with 'adam' as name into the table JFORUM_USERS? How does JForum prevent this kind of thing from happening?

Thanks in advance!

[Jeanne Boyarsky]

Adam,
Welcome to CodeRanch!

I was all set to say that there is a database constraint on that column forcing uniqueness, but there doesn't appear to be one.

In which case, I think they are counting on the odds of two people registering with the same id within a few seconds of each other is pretty slim.

[adam cooper]

Jeanne,

Thank you very much for your welcome and prompt reply!

You are completely right, and I even successfuly added two users with the same name by setting an appropriate breakpoint in the code.

Thanks again! ^_^

[Jeanne Boyarsky]

I gave you a cow for actually trying it out and verifying.