That is correct, and makes perfect sense if you think about it at the SQL level.
If you run that SQL statement in a SQL tool, and do not alias that
field, how would you look at the results and know which was which?
Larry
On 1/23/07, Carlos Cajina <[EMAIL PROTECTED]> wrote:
Hi!
I have a question regarding the implementation of the N+1 solution. Couldn't
find any reference in the mailing list/docs, so here's the thing:
Preconditions:
1. Using iBATIS version 2.3.0.677
2. Applied the N+1 solution to a One-to-Many tables relationship
Problem details:
1. table_b references table_a with a FK
2. table_a and table_b both have a 'name' field
3. Java classes representing those tables also have a 'name' property
Problem:
Since both tables have a 'name' field, when doing a queryForList and
traversing the resulting list of A objects that contain a list of B objects,
and calling getName() for both the parent and children objects, the returned
value is always the 'name' property value of the children objects.
I aliased the 'name' field of table_b in my query (and in the appropiate
SqlMap) and the traversing and calling of getName() in parents and children
worked as expected.
I'm guessing -from the behaviour I see- that when mapping tables that share
field names (i.e. id, name, description) the query in the SqlMap must alias
those fields so that the SqlMaps/Java objects don't "get confused". Sorry I
can't describe this in a more technical way but Is this behaviour correct?
Below is a mapping that mimics what I'm doing/using:
<resultMap class="some.package.ClassA" id="resultA" groupBy="aId">
<result column="a_id" jdbcType="INTEGER" property="aId" />
<result column="name" jdbcType="VARCHAR" property="name" />
<!-- 1:N solution -->
<result property="bList" resultMap="someNameSpace.resultB" />
</resultMap>
<resultMap class="some.package.ClassB" id="resultB">
<result column="b_id" jdbcType="INTEGER" property="bId" />
<result column="b_name" jdbcType="VARCHAR" property="name" />
<result column="componentType" jdbcType="INTEGER"
property="component_type" />
<result column="a_id" jdbcType="INTEGER" property="aId" />
</resultMap>
<select id="selectAB" parameterClass="int" resultMap="resultA">
SELECT a.a_id, a.name, b.b_id, b.nname, b.component_type, b.a_id
FROM table_a a INNER JOIN table_b b
ON (a.a_id = b.a_id)
WHERE b.component_type = #value#
ORDER BY a.name, b.name
</select>
Any comments, thoughts, ideas will be appreciated.
Regards,
Carlos
