does it will lead to automatic failure if i don't implement the cookie function?

[joe lin]

hi,alll
i decide not to send the cookie value to the client side,and hide the lock/create/delete functions from client.so i don't know what the cookie value can be use for?what do you think about? does it will lead to automatic failure?thanks for any response!

[Paul Truckle]

Hi Jo. In my assignment there is one cookie value at the beginning of the file and I think (from what I've read) that this is used to verify that the file being read (i.e. the database) is actually the correct format file. Basically U take the cookie value make it into a hard coded constant within your java app and then make sure that when you read the initial header of the database file it matches your hard coded constant.


Paul.

[Andy Zhu]

I think Joe talks about the cookie used in locking mechanism not the very first bytes on the data file.

It doesn't matter how the mechanism you use to get this cookie value, it got to be some value to uniquely identify a client which is doing the critical process on the server. Some mechanism is easier than others. Search the forum you will find one. I have a specific posting on this issue and get 80 over locking using the mechanism I proposed and proved it correct.

[joe lin]

hi all,
I think Andy has got my point,but not all.because i don't want to know what mechanism can be used to get a cookie value.i mean i needn't cookie value at all.this sequence : lock record -> update/create/delete record -> unlock record is done in the server side and surely done by the same client.because the client only invoke one method like book(...).so ,the cookie value needn't be used at all.what do you think?

[Jason Ford]

Joe,

It sounds like you have hidden the complexity of the locking mechanism from the client. I have done the same thing in my assignment. However, this doesn't free you from the need to use the cookie.

When doing the lock -> update -> unlock on the server side, you should probably use the cookie. If you don't, you probably won't fail automatically, but the grader would have a good reason for taking off points you'd rather keep.

[Andrew Monkhouse]

Hi Joe,

You are correct - in your implementation the lock cookie makes no sense at all (there is a separate argument that the lock cookie makes no sense in any circumstances, but we won't go into that ).

I would still recommend that you spend some time in ensuring that lock cookies are used correctly as specified in the interface comments. The reason for this is that in theory some other class could use your Data class, and would expect it to behave in a certain way, as specified in the instructions. If you ignore the cookie value then another programmer can no longer rely on your Data class.

Regards, Andrew

[joe lin]

hi all,
first,thanks for your reply!
original posted by Jason:

It sounds like you have hidden the complexity of the locking mechanism from the client. I have done the same thing in my assignment. However, this doesn't free you from the need to use the cookie.

Jason,could you explain more detail about that why it doesn't free me from the need to use the cookie?in my implementation i really don't rely on the cookie value.many thanks!

[Jason Ford]

Joe,

As Andrew mentioned, you should implement the cookie as specified in the interface comments. I agree that it isn't technically necessary. However, it is one of the easier requirements to implement, so why not do it?

Have you ever heard of the Halo effect? You know, where you've convinced somebody that everything you do is great and that you can do no wrong? Well, by doing little things like locking with cookies, you make it a little easier for the grader to think, "Oh, man, this Joe is a great guy."

Now, imagine that you don't implement the cookie. The grader will be inclined to think, "Oh, there's sloppy Joe again. He's always cutting corners."

So, even if you can't think of a good technical reason for implementing the functionality, you should implement it anyway. After all, that's what the interface expects.

[joe lin]

Jason,i think you are right.i will implement the cookie function in my project.i think the grader will smile for this.thanks!