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From Clinton Begin <clinton.be...@gmail.com>
Subject Re: iBATIS 3.0 selectOne SessionException if no data found
Date Fri, 28 Aug 2009 13:30:19 GMT
Going once, going twice.... consider it done.

Clinton

On Fri, Aug 28, 2009 at 2:27 AM, Thanh PHAM <dev@pham.me> wrote:

> I agree with Zoran and would prefer to return null on 0 too.
>
> 2009/8/28 Zoran Avtarovski <zoran@sparecreative.com>
>
>>  Thanks Clinton,
>>
>> I agree with you, at least I think I do.
>>
>> I think only throwing an exception on only more than one object is a great
>> idea.
>>
>> In our standard approach we often see requests for objects that have been
>> deleted. All we do is test for null and then respond appropriately. What
>> concerns me is that the current approach will have us try, catch, test to
>> see what caused the error and then respond appropriately.
>>
>> Where I’d prefer to return null on 0, object for 1 and then throw a
>> TooManyObjects error – the name of the error is irrelevant :) This way a
>> simple null test is all that is needed in non exceptional circumstances.
>>
>> Z.
>>
>>
>> This is an interesting case... It's based on two best practices:
>>
>> 1)  You should not use try/catch for flow control.  So if you're catching
>> the exception to deal with a non-exceptional (i.e. normal) case, then you're
>> probably abusing the exception.
>>
>> 2)  It's not a good idea to return null when one was requested.
>>
>> The idea here is that if you don't know how many results will be returned
>> (e.g. 0, 1 or N), then you should use selectList().  However, if you do know
>> that the instance absolutely exists, then you should use selectOne().
>>
>> If this practice seems like a lot of arm waving and not terribly
>> practical, then that's what I'd like to hear from people.  Otherwise, does
>> anyone agree with the design?  I can easily eliminate the exception on 0 or
>> 1, and instead only throw an exception on many (which makes sense).
>>
>> I agree that the exception should be better... but I don't suggest using
>> it for flow control.
>>
>> Thoughts?
>>
>> Clinton
>>
>>
>>

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