discriminator from other class??

angela · **Posted:** Thu Jun 01, 2006 6:01 am

hi all

i would like to to a subclass mapping and was wondering if a can use a discriminator from another class??

I have a mapping of table TKURS which has several columns, and a foreign key to table TANGEBOT. There are different types of KURS which i want to define in my subclass mapping.

The type of the KURS/ANGEBOT is defined in table TANGEBOT. This type i would like to use as discriminator in my TKURS hibernate-mapping file.

How does this discriminator tag look like?? I mean how can i define it to refer to the table TANGEBOT. is it possible?

Kind regards
Angela

damnhandy · **Posted:** Thu Jun 01, 2006 8:04 am

Since your discriminator values are spread out accross multiple tables, you may want to use a formula on your discriminator element. If you look at the tests folder of the Hibernate distribution, there is a folder called discriminator. This test uses a formula-based discriminator to define the subclasses. Your formula will be slightly different as you will need to join 2 tables, but it's the same basic idea.

When you encounter KURS/ANGEBOT, you'll want to use the <join> element to pull in data from the TANGEBOT table. You'll be mixing the table per class hierarchy with table per subclass as defined here:

http://www.hibernate.org/hib_docs/v3/re ... ersubclass

I've done a bit more exotic inheritence mappings before and I think this should do the trick.

Ryan-

P.S. Don't forget to rate! :)

angela · **Posted:** Thu Jun 01, 2006 10:54 am

Thanks!! That helped me a lot!! :-)

angela

sagimann · **Joined:** Sun Jun 11, 2006 10:41 am **Posts:** 164

could you please show your solution (map files) ? I'm having a similar problem and I'm not sure how to use the <join> correctly. thanks.

angela · **Posted:** Tue Jun 13, 2006 5:32 am

Hello!
this is my solution:

Code:

<hibernate-mapping>
    <class name="najsre7.model.Kurs" table="TKURS" schema="NAJSRE7_WEB" discriminator-value="0">
        <id name="id" type="java.lang.Integer">
            <meta attribute="use-in-tostring">true</meta>
            <meta attribute="use-in-equals">true</meta>
            <column name="ILAUFNUMMER" precision="9" scale="0" />
            <generator class="sequence">
                <param name="sequence">SEQ_TKURS</param>
            </generator>
        </id>
        
        <!-- <discriminator 
         type="java.lang.Integer"
         formula=" ( SELECT TAGB.INUTZERGRUPPE FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER) "/>
         -->
        
        <discriminator 
         type="java.lang.Integer"
         formula=" CASE  
                  WHEN (SELECT TAGB.INUTZERGRUPPE FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=1 THEN 1
                  WHEN (SELECT TAGB.INUTZERGRUPPE FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=2 AND (SELECT TAGB.FK_TAART_ILAUFNR FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=1 THEN 2
                  WHEN (SELECT TAGB.INUTZERGRUPPE FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=2 AND (SELECT TAGB.FK_TAART_ILAUFNR FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=2 THEN 21 
                  WHEN (SELECT TAGB.INUTZERGRUPPE FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=3 THEN 3
                  WHEN (SELECT TAGB.INUTZERGRUPPE FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=4 AND (SELECT TAGB.FK_TAART_ILAUFNR FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=3 THEN 4
                  WHEN (SELECT TAGB.INUTZERGRUPPE FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=4 AND (SELECT TAGB.FK_TAART_ILAUFNR FROM TANGEBOT TAGB WHERE FK_TANGE_ILAUFNR=TAGB.ILAUFNUMMER)=4 THEN 41 
                  ELSE 0
                  END "/>
        
        <timestamp name="mutDatum" column="DMUTDAT" />    
        <many-to-one name="angebot" class="najsre7.model.Angebot" fetch="join">
            <column name="FK_TANGE_ILAUFNR" precision="9" scale="0" not-null="true" />
        </many-to-one>
         <many-to-one name="sportart" class="najsre7.model.Sportart" fetch="join">
            <column name="FK_TSPA_ILAUFNR" precision="9" scale="0" not-null="true" />
        </many-to-one>
        <property name="gruppenName" type="java.lang.String">
            <meta attribute="use-in-tostring">true</meta>
            <meta attribute="use-in-equals">true</meta>
            <column name="SGRUPPE" length="25" not-null="true" />
        </property>
        <property name="kursStatus" type="najsre7.dao.hibernate.userType.immutable.kurs.KursStatusUT" >
            <meta attribute="use-in-tostring">true</meta>
            <meta attribute="use-in-equals">true</meta>
            <column name="ISTATUS" length="3" not-null="true" />
        </property>

       //more common properties
        
        <subclass name="najsre7.model.KursNutzergruppe1" discriminator-value="1">
         <property name="kursArt" type="najsre7.dao.hibernate.userType.immutable.kurs.KursArtUT">
               <meta attribute="use-in-tostring">true</meta>
               <meta attribute="use-in-equals">true</meta>
               <column name="SIPAR1" precision="5" scale="0" not-null="true" />
           </property>
           <property name="unterrichtsDauer" type="najsre7.dao.hibernate.userType.immutable.kurs.UnterrichtsDauerExtendedUT">
               <meta attribute="use-in-tostring">true</meta>
               <meta attribute="use-in-equals">true</meta>
               <column name="SIPAR2" precision="5" scale="0" not-null="true" />
           </property>
           //more properties
       </subclass>
       
       <subclass name="najsre7.model.KursNutzergruppe2_Allgemein" discriminator-value="2">    
          <property name="kursArt" type="najsre7.dao.hibernate.userType.immutable.kurs.KursArtExtendedUT">
               <meta attribute="use-in-tostring">true</meta>
               <meta attribute="use-in-equals">true</meta>
               <column name="SIPAR1" precision="5" scale="0" not-null="true" />
           </property>
          //more properties and so on
       </subclass>
               
    </class>
</hibernate-mapping>

regards angela

damnhandy · **Posted:** Tue Jun 13, 2006 7:34 am

Nice work Angela! Glad it worked out.

Ryan-

sagimann · **Joined:** Sun Jun 11, 2006 10:41 am **Posts:** 164

Can the discriminator COLUMN be defined on a field from a <join> operation?

for example:
<class name="MyClass" table="MYTABLE">
<id name="id" column="ID"/>
<discriminator column="Type" type="long"/>
<join table="TYPES">
<key column="TypeID"/>
<property name="type" column="Type"/>
</join>
</class>

For some reason, this doesn't work, claiming the "Type" column does not exist (for the descriminator to use). If I move the <discriminator> tag below the <join> tag, I can a mapping exception, as if the syntax is incorrect.

sagimann · **Joined:** Sun Jun 11, 2006 10:41 am **Posts:** 164

(sorry, forgot the 'code' tag)

Can the discriminator COLUMN be defined on a field from a <join> operation?

for example:

Code:

    <class name="MyClass" table="MYTABLE">
        <id name="id" column="ID"/>
        <discriminator column="Type" type="long"/>
        <join table="TYPES">
            <key column="TypeID"/>
            <property name="type" column="Type"/>
        </join>
    </class>

For some reason, this doesn't work, claiming the "Type" column does not exist (for the descriminator to use). If I move the <discriminator> tag below the <join> tag, I can a mapping exception, as if the syntax is incorrect.

sagimann · **Joined:** Sun Jun 11, 2006 10:41 am **Posts:** 164

I've tested your solution and it does work, but there are several SQL statements created in order to do this, instead of the straightforward INNER JOIN that would have done the trick, no?
In addition, the formula is SQLServer-specific, which makes portability a problem.
Isn't there a way to do this and cause hibernate to use a simple INNER JOIN?