Jdbc & locking

Question

I am creating a database that needs to lock users out of updating certain portions if another user is currently updating the same portion.
I currently have a "locked" column in table, which is set the the user i.d. of whichever user currently owns that lock. No other user is allowed to obtain that lock until the first user releases it.
I need to write a Java method that will obtain the lock if it is available, then return the name of the user that currently owns the lock. I could do something like:
"UPDATE lockTable set owner='User A' WHERE portion=12 and owner=null"
return "SELECT owner FROM lockTable WHERE portion = 12"But this suffers from a problem: another user could unlock portion 12 between running the two queries, and the method would return null.
Can anyone help me?
Thanks you!

Answer 1

I am using separate objects for each table in my
database. But havent used finally() to close the
connections. At the very least, this is something you must do.
When we are creating a connection pool manager, what
happens when the connection is closed? With a connection pool manager, connections should not be closed -- they should only be retrieved and returned from the connection pool.
Whether the
object is returned or waits for the garbage collector
to return the object to the pool?Generally, you need to explicitly return the connection to the pool. This implies that you need to correctly handle exceptions and such in order to guarantee that connections get returned (this means proper finally blocks with proper exception handling). Otherwise you will obtain a connection pool leak and run out of available connections.
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