- The daos in previous versions did not catch any exception such as no
row found. This has been covered by catching the exceptions.
- Also refined some of the method of dao classes.
- Another feature added in this version is that tutor can not be added
with any arbitary subject_id as the inser method of tutorDao first
checks of the corresponding subject exists in the subject table. If not
it will log a warning saying subject does not exists.