O-R Relations in Sun J2EE SERVER/OC4j

Question

The O-R Mappings in Sun J2EE SERVER using Deployer Tool
Not working ...
I badly need help....

Answer 1

Raj -
You can use an old style (pfd 1 I think) of the ejb2.0 cmp/cmr with OC4J/Orion. The container will manage the relationships for you. I use it quite frequently in fact, though it is not advertised too heavily in the documentation. Once the ejb2.0 spec is incorporated fully into OC4J - you will have to make the odd change here-and-there.
For instance, create your abstract implementation classes -
Dept and Emp...
public abstract class DeptEJB implements EnityBean
//abstract getters/setters
public abstract void setDeptName(String deptName);
public abstract String getDeptName();
(etc)
// abstract 1-* relationship methods
public void addEmp(Emp emp) throws RemoteException,FinderException,NamingException,CreateException
this.getEmps().add(emp);
public abstract void setEmps(Collection emps);
public abstract Collection getEmps();
Create your abstract implementation class for Emp as well. While this relationship is certainly bi-directional (i.e. known to both) I am only doing a uni-directional relationship in this case.
After you have done this, you will need to put the relationship into the ejb-jar.xml file....You will need to create an ejb2.0 style descriptor.
For instance....
<?xml version = '1.0' encoding = 'windows-1252'?>
<!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar>
<enterprise-beans>
<entity>
<description>Dept Entity Bean</description>
<display-name>Department</display-name>
<ejb-name>Dept</ejb-name>
<home>mypackage.DeptHome</home>
<remote>mypackage.Dept</remote>
<ejb-class>mypackage.impl.DeptEJB</ejb-class>
<persistence-type>Container</persistence-type>
<prim-key-class>java.lang.String</prim-key-class>
<abstract-schema-name>Dept</abstract-schema-name>
<cmp-version>2.X</cmp-version>
<reentrant>False</reentrant>
... Put all of your cmp fields as usual...
... In that same list (different than current ejb2.0)...
... place your cmr field ...
<cmp-field>
<field-name>emps</field-name>
</cmp-field>
</entity>
<!-- Also do you Emp entity descriptor -->
<entity>
<description>Emp Entity Bean</description>
<display-name>Employee</display-name>
<ejb-name>Empejb-name>
<home>mypackage.EmpHome</home>
<remote>mypackage.Emp</remote>
<ejb-class>mypackage.impl.EmpEJB</ejb-class>
<persistence-type>Container</persistence-type>
<prim-key-class>java.lang.String</prim-key-class>
<abstract-schema-name>Emp</abstract-schema-name>
<cmp-version>2.X</cmp-version>
<reentrant>False</reentrant>
... Put all of your cmp fields as usual...
<cmp-field>
<field-name>some_field</field-name>
</cmp-field>
... etc ...
</entity>
... The rest of your enterprise bean information
</enterprise-beans>
..... Next comes the relationships section ...
<<<<<NOTE - this differs somewhat from the final EJB2.0 spec
<<<<and you will need to make any required changes once it
<<<becomes final in OC4J
<relationships>
<ejb-relation>
     <ejb-relation-name>dept-emps</ejb-relation-name>
     <ejb-relationship-role>
     <ejb-relationship-role-name>
          dept-has-emps
     </ejb-relationship-role-name>
          <multiplicity>one</multiplicity>
          <role-source>
          <ejb-name>Dept</ejb-name>
          </role-source>
          <cmr-field>
          <cmr-field-name>emps</cmr-field-name>
          <cmr-field-type>java.util.Collection</cmr-field-type>
          </cmr-field>
     </ejb-relationship-role>
     <ejb-relationship-role>
     <ejb-relationship-role-name>
          emps-belong-to-dept
     </ejb-relationship-role-name>
     <multiplicity>many</multiplicity>
     <role-source>
     <ejb-name>Emp</ejb-name>
     </role-source>
     </ejb-relationship-role>
</ejb-relation>
</relationships>
... Finish off your deployment descriptor as usual
When deployed successfully, OC4J will create your entity tables and your relationship tables (build off of the primary ids of you entity beans). You can add and remove employees from your dept.
Okay - that is a quick way to look at it from ejb2.0 (as it exists today in OC4J) container managed relationships. As stated, this will change somewhat when the spec is finalized in OC4J (they are quiet about when that will happen).
If you want to do container managed relationships in ejb1.1 - go to the Orion support site www.atlassian.com and go to this link:
http://kb.atlassian.com/content/orionsupport/articles/complex-or.html
Hope I have helped somewhat and haven't completely confused the issue!
Cheers
Ray
Thanx for the information...
I am Using J2EE RI Server ...
can i have an example Code like Dept-Emp with 1-* Relation Ship
i am trying the same...
Plz clarify...
* Shouls We Create the Relation ship fields and relation
in the DataBase itself
OR
The Container Will Manage for us
Cheers
Raj