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:ric...@gmail.com>ric...@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:t...@arasoft.de>t...@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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