Error codes within exception vs exceptions hierarchy

From my experience exception codes are used mostly as information message for user.

I didn't saw even once that somebody try to parse general exception message in order to react differently depends on error code, usually it's done via exception hierarchy.

From another hand it could be hard to create new exception subclass for every particular case and then exception codes are used.
For example, if for user code it doesn't meter why transaction failed, it should rollback it any way, but for end user it's important why it happened (wrong params, database connection or else).

So, to summarize, if you'r expecting different ways to handle different situations it's better to use different exception types, but if you should handle few problems in the same way but only notify user about particular cause it's easier to use exception codes.

Error codes are useful when

• you can't display a complete error message (dish washer display)
• the code has to be processed internally (some logic is triggered if a certain code appears or a server sends an error code to the client while the client is responsible for the message)
• we have a great manual and the user can use the code to get comprehensive information
• The user does not need to know, what happend, but has to contact the vendor

So, most time, I don't see any added value in error codes. I prefer an exception hierarchy or at least clear error message that are really useful, when found in a logfile (even 2 years after the programmer has left the company).

If you have requirements for error codes - the solution is not bad. Consider collecting all error codes in a central repository (a properties file) so that you can exchange the complete set easily:

myexception.ERROR_CODE_INVALID_NAME=text or number
myexception.ERROR_CODE_INVALID_ID=text or number