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From "Ninck Blok, Jeroen" <jeroen.ninck.b...@logica.com>
Subject Circular Relationships Mapping
Date Thu, 15 May 2008 12:40:00 GMT
Hi All,

 

I am relative new to iBatis and want to use it to map a circular relationship. However I am
experiencing some problems doing this.

I have two entities in Java: Set and Scenario. A Set can have zero or more scenarios and a
set can have zero or more sets. I have created the following structure in the database: A
table sets (with primary key set_id), a table scenarios (with primary key scenario_id) and
a linking table scenario_sets (with a foreign key to scenario_id and twice to set_id: one
for the parent set and for the child set).

 

I use the following mapping structure:

      <resultMap id="set" class="Set">

            <result property="setId" column="set_id"/>

            <result property="name" column="name"/>

            <result property="scenarios" column="set_id" select="getChildScenariosForSet"/>

            <result property="sets" column="set_id" select="getChildSetsForSet"/>

      </resultMap>

      <resultMap id="scenario-simple" class="Scenario">

            <result property="scenarioId" column="scenario_id"/>

            <result property="name" column="name"/>

            <result property="count" column="count"/>

            <result property="displayId" column="display_id"/>

            <result property="description" column="description"/>

      </resultMap>

 

With the following select queries:

      <select id="getScenario" parameterClass="Scenario" resultMap="scenario">

            select *

            from scenarios

            where scenario_id = #scenarioId#

      </select>

      <select id="getAllSets" resultMap="set">

            select s.*

            from sets s

            where not exists (

                  select 1

                  from scenario_sets ss

                  where ss.set_id = s.set_id

            )

      </select>

      <select id="getChildScenariosForSet" parameterClass="int" resultMap="scenario-simple">

            select s.*

            from scenarios s,

                   scenario_sets ss

            where ss.parent_set_id = #value#

            and s.scenario_id = ss.scenario_id

      </select>

      <select id="getChildSetsForSet" parameterClass="int" resultMap="set">

            select s.*

            from sets s,

                   scenario_sets ss

            where ss.parent_set_id = #value#

            and s.set_id = ss.set_id

      </select>

 

The Set class has got two lists. One for Set instances and one for Scenario instances.

When I fill the database like this:

-          Set 1

o   Set 2

§  Set 3

§  Set 4

o   Set 5

-          Set 6

 

Now when I call getAllSets it does not fully populate the child sets. Set 4 is not added to
the list of Set 2, though I would expect this to happen. On page 39 of the developer guide
I found a warning concerning circular relationships, however I did not find a (fitting) solution
for more problem, since the number of child sets (and the level of child sets) is unlimited.

Is it possible to do the above with iBatis and I am doing it correctly?

 

Thanks!

 

Jeroen Ninck Blok



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