NX: Questions about DB server

[David Chan]

My assignment URLyBird v1.2.2. I have some questions to develop the db server:
1. Is it necessary to validate the data when reading the db file?
2. Is it a good idea to use java class Vector to store the record? (By using this object, I can call wait() and notifyAll() method in my locking mechanism.)
3. In coding, need to set private to each instance variable in order to minimize the variable scope? (Cannot use default or protected modifier?)
4. In coding, in normal situation, no need explicitly to set final to the method, right?

Thank you
SCJP, SCWCD
David

[Andrew Monkhouse]

Hi David,

I don't think so.
In some ways this depends on whether you are developing a "database" server or a "hotel bookings" server. If the former, you could only validate the data against the schema (which has everything as Strings, so it should all validate). If the later, then you could validate against the data that you know is meant to be contained in the fields.

Well you can use wait() and notify() with any object. So the real question is what do you want to store and what are your requirements for storing it. This will lead you to the best object to store it in.

It is a good idea to minimize variable visability and scope. But whether you make variables private or use some other modifier (or use method variables instead of instance/class variables) is something that you will have to decide on a case by case basis. As you develop your solution, you will have to decide the correct scope and visibility for each variable / method.

Not only no need - why would you want to?

Regards, Andrew

[Ramses Tutoli]

In my Data() class I validate the db file by checking for the magic cookie at the beginning of the file. If it's not valid, I throw an exception. My Server and Client GUI's catch the exception and display an error message. I don't know if it's necessary, but it's not difficult.