Why i can't catch ConstraintViolationException exception ?

[Nakataa Kokuyo]

Good day,

In order to avoid record insertion with same unique value, i try following but it seem doesn't catch the ConstraintViolationException at all but i got the error show below:

@Transactional(propagation = Propagation.REQUIRES_NEW)
		public void doInsertUser(User paramUser) {					
				try{						
					user.InsertRecord(paramUser);	

				}
				catch(ConstraintViolationException  e){														
					throw new MyOwnException("this is contraint Violation issue");	
				}
				
		}

Error that i experiencing:

ERROR org.hibernate.engine.jdbc.spi.SqlExceptionHelper - Duplicate entry 'user1name' for key 'name'

Appreciated your guidance!

[Greg Charles]

Are you sure that user.InsertRecord() throws a ConstraintViolationException? It seems that SQLException would be more likely. That log statement you're getting is definitely based on a SQLException.

(Note: Don't capitalize method names. user.insertRecord(paramUser) is in line with Java coding standards.)

[Nakataa Kokuyo]

Hi Greg, Thanks for reply!

in the debugger, it show me persistenceException and the cause is ConstraintViolationException, if i using SQLEXception, it doesn't allow to put try catch and prompt below message.

Unreachable catch block for SQLException. This exception is never thrown from the try statement body

p/s : using hibernate and JPA

[Greg Charles]

Well, that's confusing then. The JavaDoc for org.hibernate.engine.jdbc.spi.SqlExceptionHelper says:

Helper for handling SQLExceptions in various manners.

If it doesn't get thrown out of InsertRecord(), then the SQLException is being handled inside InsertRecord() or something that it calls. That handler might rethrow a ConstraintViolationException. I don't have Hibernate set up now, so I can't test that. When you say, you see it in the debugger, do you mean an actual debugger stopped at a break point, or are you seeing it in a log file? If it's a break point, then at which line is it?

I can only think of a couple of ways the catch clause at lines 7 - 9 could fail to catch the exception:

1. The exception is thrown from somewhere else other than the try block.
2. There are more than one class named ContraintViolationException, but in different packages, and your imports are set so that you are not catching the type that is being thrown.

Those are pretty much the only possibilities.

[Nakataa Kokuyo]

You could be right Greg, i observed the exception throw before the persistence exception, but how can we handle it ?

@Transactional(propagation = Propagation.REQUIRES_NEW)  
        public void doInsertUser(User paramUser) {                    
                try{                          
                    user.InsertRecord(paramUser);     
  
                }  
                catch(ConstraintViolationException  e){                                                       
                    throw new MyOwnException("this is contraint Violation issue");    
                } 
               catch(PersistenceException e){                                                       
                   logger.info("this is PersistenceException exception throw");    
                }  
                  
        }  

[Greg Charles]

I think I understand what's going on. When you said, "in the debugger, it show me persistenceException and the cause is ConstraintViolationException", you mean you saw a stack track (a series of class names and line numbers), and then a "Caused By", and another stack trace. That means the type of the exception is really PersistenceException. It wraps a ConstraintViolationException, but that's just to provide you with more information about where and why the exception occurred. It doesn't affect the program flow in any way. So, since the code in the try block throws a PersistenceException, the catch block must catch a PersistenceException (or one of its superclasses up to Throwable). The latest code posting you made should work.

[Nakataa Kokuyo]

Greg, what i plan is really throw the exception if it is ConstraintViolationException exception bacause some fields in database have been set as unique(ie:username) and to ensure no duplicate record, persistenceException seem very general in this case, how could we handle and throw if the PersistenceException exception wrapped with ConstraintViolationException ?

[Greg Charles]

If PersisitenceException is what's thrown by (I assume) code you can't control, then you have no choice but to catch and handle that. In the handler (i.e., catch block), if you absolutely have to, you can extract the wrapped ConstraintViolationException using the getCause() method, and from there you can proceed exactly as if that was the exception you caught. I don't exactly recommend that, but it is possible.

[mo ni]

Just came across a similar issue, and my "a-ha" moment was when (during debugging) I understood that the exception is not thrown in "user.InsertRecord(paramUser);", but on committing of the transaction. This is why the catch is not working, the exception is thrown later. If I wrap the place which is calling "doInsertUser", then everything works. Not sure if this is the correct way though, looks quite ugly.