How to customize TaskInstance?

[lisaanm]

Hi.,
I want to customize TaskInstance by extending it. I read the doc and forum discussions about it: I had done like
- create a subclass of TaskInstance (did)
- update the property jbpm.task.instance.class to specify the name of custom class (did)

- create a mapping file for the subclass, for mapping the extra properties you want to save

I tried to extend TaskInstance in my custom subclass mapping file, but I'm getting exception "No discriminator found for [subclass]. Discriminator is needed when 'single-table-per-hiearchy' is used and a class has subclasses"


Any help is greatly appreciated.
(sample code, if possible)

Thanks.

[coby]

I struggled with this a while, and couldn't ever get my new mapping file to play nice with the existing (umodified) TaskInstance.hbm.xml mapping file.

I'm not very familiar with hibernate, but the info at this http://ndpsoftware.com/HibernateMappingCheatSheet.html helped me figure out what needed to be done (see the Subclasses section).

It seems that when you want to use a 'single-table-per-hierarchy' that you need to add a discrimintor to the superclass mapping file (as well as the subclass mapping file). So, I ended up creating a new hibernate mapping file (MyTaskInstance.hbm.xml) that looks something like this...

<?xml version="1.0"?>

<!DOCTYPE hibernate-mapping PUBLIC
 "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
 "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping default-access="field">

 <!-- this class mapping is an exact copy of the stock
 TaskInstance.hbm.xml mapping, except a discrimintor
 column (and value) have been added to support
 a subclass that can share the same table -->
 <class name="org.jbpm.taskmgmt.exe.TaskInstance"
 table="JBPM_TASKINSTANCE"
 discriminator-value="T"
 lazy="false">
 <id name="id" column="ID_"><generator class="native" /></id>

 <discriminator column="subclass" type="character"/>

 <property name="name" column="NAME_" />
 <property name="description" column="DESCRIPTION_" length="4000"/>
 <property name="actorId" column="ACTORID_" index="IDX_TASK_ACTORID"/>
 <property name="create" column="CREATE_" />
 <property name="start" column="START_" />
 <property name="end" column="END_" />
 <property name="dueDate" column="DUEDATE_" />
 <property name="priority" column="PRIORITY_" />
 <property name="isCancelled" column="ISCANCELLED_" />
 <property name="isSignalling" column="ISSIGNALLING_" />
 <property name="isBlocking" column="ISBLOCKING_" />

 <many-to-one name="task"
 column="TASK_"
 foreign-key="FK_TASKINST_TASK"/>
 <many-to-one name="token"
 column="TOKEN_"
 foreign-key="FK_TASKINST_TOKEN"/>
 <many-to-one name="swimlaneInstance"
 column="SWIMLANINSTANCE_"
 foreign-key="FK_TASKINST_SLINST"/>
 <many-to-one name="taskMgmtInstance"
 column="TASKMGMTINSTANCE_"
 foreign-key="FK_TASKINST_TMINST"/>

 <set name="pooledActors"
 cascade="all"
 table="JBPM_TASKACTORPOOL">
 <key column="TASKINSTANCE_" foreign-key="FK_TASKACTPL_TSKI"/>
 <many-to-many class="org.jbpm.taskmgmt.exe.PooledActor" column="POOLEDACTOR_" />
 </set>
 <list name="comments" cascade="all" >
 <key column="TASKINSTANCE_" />
 <index column="TASKINSTANCEINDEX_" />
 <one-to-many class="org.jbpm.graph.exe.Comment" />
 </list>


 <!-- This is the new subclass, it has one additional
 field (customKey) that needs to be persisted too -->
 <subclass name="myapp.MyTaskInstance"
 extends="org.jbpm.taskmgmt.exe.TaskInstance"
 discriminator-value="M"
 lazy="false">
 <property name="customKey" column="CUSTOMKEY_" />
 </subclass>

 </class>

</hibernate-mapping>

Then, I removed the entry in hibernate.cfg.xml that said...

<mapping resource="org/jbpm/taskmgmt/exe/TaskInstance.hbm.xml"/>

And replaced it with a line that says...

<mapping resource="myapp/MyTaskInstance.hbm.xml"/>

I would have prefered to find a way of accomplishing the same results without having to muck with the superclass mapping file, but this seemed to work out ok.

[kukeltje]

it's not sample 'code' you need, it's a config example. This is a hibernate config issue. search the hibernate forums for this, I think you'll find something.

http://forums.hibernate.org/viewtopic.php?t=939394&view=next&sid=00ce4a4831ab25fb3e0f13afe878d5e0

[admin]

the mapping file of the task instance should be updated to this: (next 3.1 releases will include this update)

<class name="org.jbpm.taskmgmt.exe.TaskInstance"
 table="JBPM_TASKINSTANCE"
 discriminator-value="T">
 <id name="id" column="ID_"><generator class="native" /></id>
 <discriminator type="char" column="CLASS_"/>

now you just have to make sure that you include the discriminator-value attribute in your subclasses with a different value in then 'T'

i think that should solve it.

regards, tom.

[thats_jbpm]

Hi,

I also hope the same to change the discriminator-value attribute insteadof 'T' in the mapping file. This could be work then.

Regards

[lisaanm]

Thanks for your replies.

[B]Happy to know that the next jBPM release comes with discriminator value.

[lisaanm]

Thanks for your replies.

Happy to know that the next jBPM release comes with discriminator value.

Greetz.