CAF Entity locking HELP

Question

hello
I am doing some tests in WebDynpro and CAF Core services.
I have a piece of code as below that retrieves an entity from CAF Core for update. I need this entity to be locked during the update but the two methods lock() and unlock() do nothing. I can still access for update the same entity instance from another user.
This probably works if the transaction is happening within CAF service but I also need to lock entities from webdynpro when doing complex updates. In other words I am not willing to create a custom method in CAF service for each update I need to implement in webdynpro.
Any advice ? How are we supposed to use the class com.sap.tc.col.client.generic.api.LockStrategy ? I did not find much about this api.
Thanks in advance
Vitaliano
  public void UpdateKAMInTransaction( )
    //@@begin UpdateKAMInTransaction()
     IServiceFacade serviceFacade = CAFServiceFactory.getServiceFacade(cplxmdlDefinition.class);
    String guid = wdContext.currentAKamElement().getGuid();
     AKam akam = MyAppProxy.readKam(guid);
     //locking is not working at all. concurrent changes are lost
     akam.lock(LockStrategy.EXCLUSIVE);
     //update a value here
     akam.setVersion(akam.getVersion() + 1);
     akam.getAspect().sendChanges();
     serviceFacade.save();
     //locking is not working at all. concurrent changes are lost
     akam.unlock();
     wdThis.wdGetAPI().getMessageManager().reportSuccess("done update AKAM=" + akam);
    //@@end

Answer 1

Now I feel lost. Please keep helping a newby.
I have implemented my custom method in CAF Services. Here I lock the entity, make all my chanegs, then update and return. I call this custom CAF Application Service method from WebDynpro.
Nevertheless I noticed that concurrency can still happen. If more than one user updates the same entity at the same time, and exception is thrown in the log files but no exception is thrown. I.e. I cannot intercept the collision.
in the log file a huge stacktrace is written, while the most interesting message is "javax.jdo.JDOUserException: optimistic transaction failed".
So... what am I doing wrong here? Should'nt new locking just hold until the existing one is released?
HELP!
Vitaliano
     public java.lang.String myUpdateKam(java.lang.String guid, long newVersion) throws com.sap.caf.rt.exception.ServiceException
          // logging
          java.lang.String CAF_user = sessionContext.getCallerPrincipal().getName();
          java.lang.String CAF_methodHeader = MyAppBean.JARM_REQUEST + ":" + "myUpdateKam(java.lang.String, long)";
          Object[] CAF_parameters = new Object[] { guid, new java.lang.Long(newVersion)};
          com.sap.caf.rt.util.CAFPublicLogger.entering(CAF_user, MyAppBean.JARM_REQUEST, CAF_methodHeader, MyAppBean.location, CAF_parameters);
          java.lang.String retValue;
          try
               //@@custom code start - myUpdateKam(java.lang.String, long)
               //Read the BO and prepare for changes
               retValue = "";
               Kam kam = getKamService().read(guid);
               char modeLock = IBusinessEntityService.MODE_WRITE;
               try
                    //Lock BO before updating
                    try
                         getKamService().lock(kam.getKey(), modeLock, 3000);
                         retValue += "-lock-";
                    catch (CAFLockException e)
                         retValue += e.getMessage();
                    //Now do the update and commit
                    // =====> NOTE: regardelss if there is another update in progress,
                    // a concurrent update still gets down to here. WHY ?
                    long counter = kam.getVersion();
                    kam.setVersion(++counter);
                    getKamService().update(kam);
                    retValue += "-update-";
               catch (CAFUpdateException e)
                    //This case is when concurrent update occurs
                    retValue += e.getMessage();
               catch (Exception e)
                    //any other exception thrown?
                    retValue += e.getMessage();
               finally
                    //Make sure we always leave our BO unlocked
                    try
                         getKamService().unlock(kam.getKey(), modeLock);
                         retValue += "-unlock-";
                    catch (CAFLockException e)
                         retValue += e.getMessage();
               //@@custom code end - myUpdateKam(java.lang.String, long)
               return retValue;
          finally
               com.sap.caf.rt.util.CAFPublicLogger.exiting(CAF_user, MyAppBean.JARM_REQUEST, CAF_methodHeader, MyAppBean.location, CAF_parameters);
This is the code in WebDynpro to invoke CAF custom method.
  public void UpdateKAMRemotely( )
    //@@begin UpdateKAMRemotely()
     IServiceFacade serviceFacade = CAFServiceFactory.getServiceFacade(cplxmdlDefinition.class);
     IAspect retValue = null;
     for (int i = 1; i < 101; i++)
          long newLong = wdContext.currentAKamElement().getVersion() +i;
          retValue = MyAppProxy.myUpdateKam(wdContext.currentAKamElement().getGuid(),newLong);
          IAspectRow row = retValue.getAspectRow(0);
          String retMsg = row.getAttributeAsString("value");
          wdThis.wdGetAPI().getMessageManager().reportSuccess("IAspectRow=" + row + "index="+i);
          serviceFacade.save();
    //@@end
Message was edited by:
        Vitaliano Trecca