Facade interface

Question

Hey,
I have SWT client that communicate with the server via facade.
The facade layer is a group of stateless session beans.
I want to get advices from you about handling exceptions.
1.     As I mentioned above the fa�ade is stateless session bean (ejb3) and the transaction is CMT, which means that the transaction is closed and committed after my method ended. The problem with this is that the client gets unclear exceptions like DB vendor exception or hibernate exception in case of commit failure. I want to hear what are you doing?
2.     If inner component in the server throw an exception the above layer wrap this exception and throw it to the layer above in case it catch the exception. In the fa�ade I cant wrap the exception I get and throw it to the client, because the client doesn�t know the inner server exception or third-party exception, so it will get class not found.. in order to solve this I have catch(Exception) in the fa�ade that throw new ServerClientException , but in this way I lose a lot of information regarded to the underline reasons to the exception. I be happy to hear your opinion about this.
Thank you

Answer 1

Lets take an example the client try to delete user , in the server i call to manager.delete ...
This user cant be deleted because that another object has reference to this user.You should look at the requirements. If the client is initiating an operation that goes against the referential integrity (RI) of the database, you should change the client code, change your server facade, or loosen the RI by making a bidirectional relationship unidirectional.
I'd change the server facade; make the EJB go through the proper sequence of steps to remove the related entities. For example, "deleteUser" doesn't just call em.remove(user). It checks for dependent objects and throw a proper exception.
public void deleteUser(Integer _userId) throws TransactionsPendingException {
User user = em.find(User.class, _userId);
if( user.getPendingTransactions().size() > 0 ) {
  throw new TransactionsPendingException();
em.remove(user);
another issue is the chain issue:
in some cases the client need to dispaly information on the exception to the user , so i throw the excpetion to the client , but the excpetion contain inner server exception. is not good that the client will be depend in server package, so i get there classnotfound.In addition to the server package and the client package, create a common package of exceptions that is compiled, JAR-ed, and deployed with both the server and the client.