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From Poitras Christian <Christian.Poit...@ircm.qc.ca>
Subject RE: iBATIS 3.0 selectOne SessionException if no data found
Date Thu, 27 Aug 2009 14:05:34 GMT
How about subclassing SessionException with something like NoResultFoundException?
That way, it would be easy to catch the exception (the user mispelled his email, probably)
and show a simple error to the user.

Christian

-----Original Message-----
From: Thomas G. Schuessler [mailto:tgs@arasoft.de]
Sent: Thursday, August 27, 2009 9:43 AM
To: user-java@ibatis.apache.org
Subject: Re: iBATIS 3.0 selectOne SessionException if no data found

1. @Rick: Thank you for your solution, I will use it.
2. @Clinton: No, I don't want NULL, an exception is the right approach. But the exception
needs to have reliable information about the specific cause, just like the SqlState field
in SqlException, so that one can differentiate between an expected situation (no data for
the given key) and other ("real") errors (database disappeared...).

BTW, I love the 3.0 version so far...



At 08:12 2009-08-27, Clinton Begin wrote:
>Rick's suggestion is correct.  That was the idea.
>
>Honestly, we don't have to throw the exception, but it is a good in
>practice IMHO...
>
>But you all tell me, do you really want to return null?
>
>Clinton
>
>On Wed, Aug 26, 2009 at 11:07 AM, Rick
><<mailto:rickcr@gmail.com>rickcr@gmail.com> wrote:
>Maybe a bit of a hack but ...
>
>public interface UserMapper {
>  public List<Long> getUserIds(String email); }
>
>Keep the dao method the same...
>
>public long getUserId(String email) {
>
>but just do a quick check in there on the size of the List returned,
>and do what you want with it (throw you own exception if over size 1?)
>
>and then just always return list.get(0)
>
>
>On Wed, Aug 26, 2009 at 11:21 AM, Thomas G.
>Schuessler <<mailto:tgs@arasoft.de>tgs@arasoft.de> wrote:
>
>In my MySQL db, I have a table 'users' with (amongst others) these fields:
>
>  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,  `email` varchar(120)
> NOT NULL,
>
>In UserMapper.java I have the following method
>
>public interface UserMapper {
>  public long getUserId(String email);
>}
>
>In UserMapper.xml I have this:
>
><select id="getUserId" parameterType="string" resultType="long"> SELECT
>id FROM users WHERE email = #{email} </select>
>
>My DAO client code looks like this
>
>public long getUserId(String email) throws SQLException {
>        SqlSession session = sqlSessionFactory.openSession(true);
>        try {
>                UserMapper mapper = session.getMapper(UserMapper.class);
>                long userId = mapper.getUserId(email.toLowerCase());
>                return userId;
>        } catch (SessionException sex) {
>                throw new SQLException("No data found.", "02000");
>        } finally {
>                session.close();
>        }
>}
>
>What I am unhappy about is that in order to differentiate between the
>"no data found"
>situation and other cases, I  would have to check the SessionException
>for the string "Expected one result to be returned by selectOne(), but
>found: 0".
>This is somehow unsatisfactory (at least to me) since I do not like to
>trust that string to never change...
>
>Is there another way to deal with the situation (without an additional
>SELECT COUNT...)? Maybe I have not found the optimal way to solve the
>issue?
>Otherwise, I´d like either a specific exception for this (and similar)
>cases, or a field with an error code in SessionException.
>
>Thank you for any input on this,
>Thomas
>
>
>
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>
>
>
>--
>Rick R
>


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