locking and cookies

[Keith Jones]

Hi all,

I wonder if someone can explain to me what I have to store in the Map object in the update method. The Map obviously maps a key to a value.

Either the value or the key will be the recNo parameter but what about the other variable? I have seen the word cookie being bandied around? What's this for and how is it generated?

Any help regarding this will be appreciated.

[Smith Jone]

Hi,Keith Jones

I don't have the Cookie in my UrlyBird version.you too
But, other versions have the cookie.

  public void lock(int recNo,int cookie) throws RecordNotFoundException  

We don`t need to make a cookie beacuse of aother version.

If you want to make cookie,Look at the following code.

  cookieNumber = Thread.currentThread().hashCode();
lockedRecords.put(record,cookieNumber);  

Cheer up Jones


[ November 21, 2006: Message edited by: Smith Jone ]

[Keith Jones]

Hi there,

Thanks for the reply. Yes I guess I should smile more.

Ok so let me get this straight since we both don't have a signature which requires a cookie that means

1. we don't need to store a cookie
2. we don't need to have a datastructure that stores key value pairs (we can use an arraylist instead for example)
3. we can put a cookie in if we want to in the way you described

Cheers, and still smiling

[Smith Jone]

1. we don't need to store a cookie
2. we don't need to have a datastructure that stores key value pairs (we can use an arraylist instead for example)
3. we can put a cookie in if we want to in the way you described

OK,I understood that you said.
Of course,You should use arraylist or vector in Locking method.
But, You&I may have a datastructure that stores key value paris.
Because Anything will do. (in this case - Locking mechanism)


By the way,You applied Object Adapter Pattern in Database,too ??


http://www.coderanch.com/t/188772/java-developer-SCJD/certification/Adapter-Pattern
[ November 21, 2006: Message edited by: Smith Jone ]

[Keith Jones]

Hi,

No I'm not using the Adapter pattern or anything fancy like that. I read your post and unfortunately I don't understand what's going on there. It seems a bit complicated. All I'm doing is catching IOExceptions etc inside my methods. That's one way of getting around it.

As for cookies - are you personally storing them? If so what use are they to us?

[Smith Jone]

Yes, I use Cookie,just in case.As following code...
How do you implement Locking?

public class LockManager extends Data {
    private final Map<Integer,Long> lockedRecords =  Collections.synchronizedMap(new HashMap());
 
.....
 
public synchronized void lock(int recNo) throws RecordNotFoundException {
 
Integer record = new Integer(recNo);
Integer lockDB = new Integer(DATABASE_LOCK);
long cookieNumber = 0L;
 
if(recNo < 1) throw new RecordNotFoundException();

try 
{
    if( recNo == DATABASE_LOCK )
{
while( lockedRecords.containsKey(lockDB))
{
wait();
}
} else {
    while(isLocked(recNo))
{
wait();
}
}    
 
cookieNumber = Thread.currentThread().hashCode();
lockedRecords.put(record,cookieNumber);
 
} catch (InterruptedException ie) {
System.out.println("Locking Fail : " + recNo);
System.out.println(ie.getMessage());
}
}

But,Cookie is a good-for-nothing so far.
[ November 21, 2006: Message edited by: Smith Jone ]

[Keith Jones]

wow that looks very complicated. I've not got to this stage yet I'm still working on the update method