How to write the mapping file

ragarwal · **Joined:** Fri Apr 07, 2006 7:16 pm **Posts:** 3

I have the following class heirarchy (getter/setter excluded)

class Question {
String text;
}

class Long extends Question {
Integer maxLength;
}

class Short extends Question {
List choices;
}

class ShortWithAnswer extends Short { }

class Choice {
String choiceText;
}

class ChoiceWithAnswer extends Choice {
Boolean correct;
}

Now the list 'choices' will contain Choice objects when the questions type is Short and will contain ChoiceWithAnswer objects when the question type is ShortWithAnswer.

The table structure is as follows:

QUESTION
- qid
- text
- maxLength
- qtype (used as a discriminator)

CHOICE
- qid
- choicetext
- correct

Any help is appreciated. Thanks

Hibernate version:

2.1

Name and version of the database you are using:

Oracle 9i

kgignatyev · **Posted:** Mon Apr 10, 2006 6:32 pm

I would suggest flattening class hierarchy (just getting rid of all the inheritance), and then the mapping will be trivial.

ragarwal · **Joined:** Fri Apr 07, 2006 7:16 pm **Posts:** 3

kgignatyev wrote:

I would suggest flattening class hierarchy (just getting rid of all the inheritance), and then the mapping will be trivial.

yes but I have actually posted a simplyfied version of an existing program that I am supporting. I have added to the heirarchy and just need some help updating the mapping file. Thanks

ragarwal · **Joined:** Fri Apr 07, 2006 7:16 pm **Posts:** 3

Here is my attempt. The error I get is "Found shared references to a collection: Short.choices" at run time. I basically need some way to override the definition of the List choices.

Code:

<hibernate-mapping>
  <class name="Question" table="QUESTION" discriminator-value="null"
      dynamic-update="true" polymorphism="explicit">

  <!-- Discriminator -->
  <discriminator column="QUESTION_TYPE" type="character" not-null="true"/>
  
  <!-- Base class -->
  <property name="text" column="LONG_TEXT" not-null="true"/>
      
  <!-- Subclass QuestionLong -->
  <subclass name="Long" discriminator-value="L">
     <property name="maxLength" column="MAX_RESPONSE_LENGTH"/>
  </subclass>

  <!-- Subclass QuestionShort -->
     <subclass name="Short" discriminator-value="S">
   <list name="choices" lazy="false" table="CHOICE" outer-join="true" cascade="all">
            <key>
      <column name="QUESTION_NUMBER"/>
            </key>
                <index column="CHOICE_NUMBER"/>
   <composite-element class="Choice">
          <property name="choiceText" />         </composite-element>
                </list>
         
     <!-- Subclass QuestionWithAnswer -->
     <subclass name="QuestionWithAnswer" discriminator-value="A">
                  <list name="choices" lazy="false" table="CHOICE" outer-join="true" cascade="all">
            <key>
               <column name="QUESTION_NUMBER"/>
            </key>
                <index column="CHOICE_NUMBER"/>
            <composite-element class="ChoiceWithAnswer">
   <property name="choiceText" />               <property name="correct" column="CORRECT"/>
                  
            </composite-element>
         </list>
     </subclass>
               
  </subclass>
</class>
</hibernate-mapping>

mpeter22 · **Joined:** Tue Apr 11, 2006 4:57 am **Posts:** 17

I have exactly the same problem. We have big class hierarchy with multiple level of inheritance, and our mapping strategie will be with Table per subclass (<joined-subclass>).

How to create a mapping file?

this is probabbly a stupid question, but is this possible?
<joined-subclass>
<key ...>
<property...>
<joined-subclass>
<key ...>
<property...>
</joined-subclass>.
</joined-subclass>.

It may describe 3 level of inheritance.

This is very important guys, I need help asap !