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From "Douglas Bell" <DB...@boingo.com>
Subject RE: iBATIS 3.0 selectOne SessionException if no data found
Date Fri, 28 Aug 2009 17:26:35 GMT


From: Zoran Avtarovski [mailto:zoran@sparecreative.com] 
Sent: Thursday, August 27, 2009 4:25 PM
To: iBatis Java Mail List; Clinton Begin
Subject: Re: iBATIS 3.0 selectOne SessionException if no data found


I for one would prefer null. I like the idea of testing for null rather than using try catch


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?  


On Wed, Aug 26, 2009 at 11:07 AM, Rick <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 <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}
	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 {
	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,

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