The onRetryWriteException method receives control when a
retryable exception is thrown from an ItemWriter writeItems
method. This method receives the exception and the list of items
being written as inputs.
This method receives control in same checkpoint scope as the
ItemWriter. If this method throws a an exception, the job ends
in the FAILED state.
items - specify the items passed to an item writer.
ex - specifies the exception thrown by an item
java.lang.Exception - is thrown if an error occurs.