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From "Chris Lamey" <cla...@localmatters.com>
Subject RE: How to custom database exception?
Date Mon, 31 Dec 2007 16:29:33 GMT
That's exactly why it was a hack and is easily broken.

Like I said before, a test in the catch looked for a specific string in the SQLException's
message and threw a new custom exception that was handled appropriately elsewhere.


-----Original Message-----
From: Kezerashvili, Denis [mailto:Denis.Kezerashvili@gs.com]
Sent: Mon 12/31/2007 6:47 AM
To: user-java@ibatis.apache.org
Subject: RE: How to custom database exception?
 
You code won't be broken unless you are relying on that generated custom
exception to be caught and acted upon. If the Oracle exception has
changed for some reason it will just fall through your custom handling
piece of code. I am guessing you are rethrowing other types of
exceptions that you did not write special handling for, so you should be
fine:)
 
 
Denis


________________________________

	From: Chris Lamey [mailto:clamey@localmatters.com] 
	Sent: Saturday, December 29, 2007 9:47 AM
	To: "<user-java"@ibatis.apache.org
	Subject: RE: How to custom database exception?
	
	

	Hello, my name is Chris and I've committed this most egregious
hack.
	
	Many years ago when I was young and easily led down the dark
side, a requirement came down from on high that required a custom user
message for a specific Oracle error message.  The project was already
through the development and test phase.  Someone with an impressive
title had seen that exception in production and it had to be taken care
of.  The requirement came at me late at night and had to be implemented
immediately - there was no time to think!
	
	So in the catch block of SQLException, I tested for the specific
Oracle error ID in the exception mesage.  If it was there, I threw one
of our custom exceptions that produced the desired effect in the
application.
	
	At the time, I commented that code as something that was a hack
and had to be changed.  I promised myself I would go back and fix it.
But alas, this did not come to pass and that code is still running.
	
	It was to easy to get done at the time...it haunts me to this
day.
	
	If they switch DBs, even versions of Oracle, that code is easily
broken.  Trying to map DB specific error codes to an Exception hierarchy
is madness.  Instead, it is better to test for those conditions and
constraints up front and not to let it be an error condition.
	
	It's also good to read Josh Bloch's Effective Java for the
section on Exception handling.  He makes a pretty strong case for not
using custom Exceptions as what amounts to return codes for commonly
expected cases.
	
	Cheers,
	Chris
	
	-----Original Message-----
	From: larry.meadors@gmail.com on behalf of Larry Meadors
	Sent: Sat 12/29/2007 6:35 AM
	To: user-java@ibatis.apache.org
	Subject: Re: How to custom database exception?
	
	That's a SQL/JDBC problem, really - a unique constraint doesn't
give
	you much in terms of customizing the message. I guess if you
wanted
	to, you could look at the message and try to map it to a nicer
	message...but iBATIS isn't going to do that for you. It would be
	infeasible to map any database error message to custom
exceptions.
	
	Larry
	
	
	On Dec 28, 2007 10:59 PM, yuan gogo <gogoyuan@gmail.com> wrote:
	> Hi, all.
	>     I'm new to iBatis, and wonder how to get custom data
exception in the
	> web application.
	>
	>    Say, I have a database table Users (id, username,
password), the username
	> is UNIQUE.
	>    While insert new user data with a duplicated username , a
data exception
	> will be thrown from jdbc indicate constraint conflict on some
datafileds.
	> But I personally think throw a custom exception like
	> UsernameExistedException will be a better way for other layer
to log or
	> notify user.
	>
	>    How can I do it?
	>
	> Ps : I use Tapestry 5 + spring 2.5M + iBatis 2 + postgresql
8.3 beta +
	> tomcat 6.0.14 for evaluation.
	>
	> Thanks!
	>
	> gogoyuan [_at_] gmail.com
	>
	
	





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