Using JPA Entity-Objects defined in other EJB-Development Component

Question

Hello Community,
I'm working on a Java-Application on NW CE 7.1, using JEE5 Beans in the Business-Logic-Layer and WebDynpro/Java in the UI-Layer.
I designed a Bean for working with data, stored in a database-table of the system-database.
For that addtionally i created a class, representing the Entity-Object, in the same Development-Component of Type EJB 3.0.
It looks like this:
@NamedQueries ({
     @NamedQuery (name="findAllSdCust", query="SELECT c from SdCust c ORDER BY c.kdnr"),
     @NamedQuery (name="findSdCustByKdnr", query="SELECT c from SdCust c WHERE c.kdnr = :kdnr"),
     @NamedQuery (name="findSdCustByIlnnr", query="SELECT c from SdCust c WHERE c.ilnnr = :ilnnr")
@Entity
@Table(name="ZKALL_SD_CUST")
public class SdCust implements Serializable {
     @Id
     @TableGenerator (name="idGenerator", table="ZKALL_ID_GEN", pkColumnName="GEN_KEY", valueColumnName="GEN_VALUE", initialValue=100)
     @GeneratedValue (strategy=GenerationType.TABLE, generator="idGenerator")
     private long id;
     private String name;
     private String lname;
     private String kdnr;
     private String ilnnr;
     private long connid;
     private long cnt;
     @Version
     private long version;
      Constructor, Getter and Setter methods follow here
The corresponding bean looks like this
@Stateless(name="SdCustBean")
public class SdCustBean implements SdCustLocal {
     @PersistenceContext (unitName="xyz")
     private EntityManager em;
     public SdCust getSdCustByKdnr (String kdnr)
          SdCust result = new SdCust();
          // List<Manufacturer> resultList = new ArrayList<Manufacturer>();
          Query  myQuery = em.createNamedQuery("findSdCustByKdnr");
          myQuery.setParameter("kdnr", kdnr);
          result = (SdCust) myQuery.getSingleResult();
          return result;
     public void setEM (EntityManager iem)
          em = iem;
       // other methods .....
After that i created a new Development-Component of Enterprise Application-Type and added above DC to this EAR-DC. I also supplied the nessecary descriptor-files/Enries in EJB-DC and EAR-DC.
When now using this bean from WebDynpro with the Web-Dypro EJB-Model-Import everything works fine.
The bean returns the desired object(s).
But now i created a new DC of type EBJ 3.0
This DC contains a Message Driven Bean. That MDB is a Job-Bean which i want to schedule. That  Bean uses JRA to connect to an SAP-Abap-System to read some Data and should use JPA to insert/upate/delete the read data in the Database. This should work as a simple replication for my application.
I assigned that EJB-DC containing the MDB to a new EAR-DC together with job-definition-xml and the neccessary entries in deployment-descriptors.
After deploying i see the corresponding job-defition in the NW scheduler using the administrator-views.
I'm also able to schedule the job and it executes fine. Connecting to SAP-Abap System also works fine using JRA.
But JPA does not work!!!!!
I created an dependency from my EAR-DC containing the Job EJB-DC and to the EJB-DC containing the Entity-Class.
I tried three diferent things to get i running, but all of them failed.
1.)
The part  looks like:
public class MasterDataReplicateJobBean extends MDBJobImplementation implements MessageListener
  @EJB SdCustBean mybean;
   public void onJob(JobContext ctx) throws Exception {
        SdCust sdCust = mybean.getSdCustByKdnr (mykdnr);
Compiles fine. But this fails because the Data is stored in the system-database. The exception says, that i have to use a datasource which supports 2-Phase commit. I know, that i could possibly solve this problem by annotation the Method getSdCustByKdnr with the Annotation for the Transaction-Manager to use REQUIRES_NEW Transaction. But i dont want to generally annotate my methods this way.
2.)
This part looks like this
public class MasterDataReplicateJobBean extends MDBJobImplementation implements MessageListener
@PersistenceContext (unitName="xyz")
private EntityManager em;
   public void onJob(JobContext ctx) throws Exception {
     SdCust cust = new SdCust();
     Query  myQuery = em.createQuery("SELECT c from SdCust c WHERE c.kdnr = :kdnr");
     myQuery.setParameter("kdnr", dbkdnr);
     cust = (SdCust) myQuery.getSingleResult();
This also results in a runtime-exception because the entity-Manager cant resolve SdCust from the Query as an Object. The Exception is:
java.lang.IllegalArgumentException: line 1: Abstract Schema Type 'SdCust' doesn't exist
SELECT c from SdCust c WHERE c.kdnr = :kdnr
3.) and last try so far:
public class MasterDataReplicateJobBean extends MDBJobImplementation implements MessageListener
@PersistenceContext (unitName="xyz")
private EntityManager em;
   public void onJob(JobContext ctx) throws Exception {
     SdCustBean custBean = new SdCustBean();
     custBean.setEM(em);
     SdCust cust = custBean.getSdCustByKdnr(kdnr);
In this example i use the Bean from the beginning not as a bean itself but as a normal class. that class has an addtional Method setEM to set the Entity-Manager (which is injected when using the class as a bean)
In that way i got the exception, that the named Query "findSdCustByKdnr" cannot be found by the entity-manager.
It seems to me, that i can access the class, but that all annotations belonging to JPA for that class are not recognized.
Does anybody can give me a hint to solve this problem? Did i forgot something important?
best regards
matthias hayk
Edited by: Matthias Hayk on Feb 5, 2009 9:38 AM

Answer 1

I was already on wright trace.
My class "SdCust" was not recognized by the Entity-Manager as an Entity-Class.
This relies on the storage of the entity-class and where the Entity-Manager looks for entity-classes.
By default it seems to look for all classes in the same jar file. thats the reason why everything works fine when the using bean and the entity-class are in the same project.
In my last case, the using bean is in another  development-component and so also in anohter jar file. in this case the entity-manager must be told where to find entity-classes.
this is done in the persistence.xml file.
i added the line
<jar-file>xxx.yyy.com~mdata_beans.jar</jar-file>
underneath the <persistence-unit>-tag.
This works.
regards
Matthias Hayk