Beta Question: unlock

[Tybon Wu]

This is the method defined in the DBAccess interface:

public void unlock(long recNo, long cookie)
    throws RecordNotFoundException, RecordNotLockedException;

So what happens if the cookie passed in does not match the cookie of the locked record? Shouldn't this method also throw RecordLockedException? Right now I just do nothing if that's the case. What do you think?

[Mark Spritzler]

long cookie?
Where did you get that, in my interface it is just unlock(int record)
Mark

[Tybon Wu]

Interesting... I guess we get different versions fo the project. In my instructions it says "Version bfkq"

[Valentin Crettaz]

I have version aejb and the signature of the unlock method is like yours. I guess you are right, a RecordLockedException should be thrown in the case the record is locked but the cookie does not match...I'm not sure whether I am going to change the interface or do something else... I'll keep you posted...
And shouldn't the update (and delete) method throw RecordNotLockedException if an update is attempted without first locking it? Or should we automatically lock the record if the latter is unlocked when invoking update (or delete) and then automatically unlock it when the update (or delete) method has been performed?
[ September 06, 2002: Message edited by: Valentin Crettaz ]

[Mark Spritzler]

I have Version bfkq
and here is the interface I got.

 package suncertify.db;
public interface DBMain {
// read an entire record from a given record number
public String [] read(int recNo) throws RecordNotFoundException;
// attempt to modify the fields of a record.
// throws RecordNotFoundException if record recNo does not exist
// or is marked deleted
public void update(int recNo, String [] data)
throws RecordNotFoundException;
// delete the record, make the record number and associated disk
// storage available for reuse
// throws RecordNotFoundException if record recNo does not exist
// or is already marked deleted
public void delete(int recNo) throws RecordNotFoundException;
// determine the record number that contains a given key. Lock
// the record if lock is true.
// throws RecordNotFoundException if the key cannot be matched
// exactly
// throws RecordLockedException if lock is true, but the found
// record is already locked 
public int find(String key, boolean lock)
throws RecordNotFoundException, RecordLockedException;
// determine the record numbers that match any non-null element
// of the criteria array.
// null fields are treated as wild cards, and matches are
// performed from the start of the field up to the end of the
// criteria string. For example, Fred matches Fred or Freddy.
// returns all matching record numbers at once.
// throws RecordNotFoundException if nothing matches the
// criteria
public int [] find(String [] criteria)
throws RecordNotFoundException;
// create a new record in the database (possibly reuse a deleted
// entry). Insert the given data, and return the record number
// of the new record.
public int create(String [] data) throws DuplicateKeyException
// lock a record so that the record is only accessible to this
// client.
// throws RecordNotFoundException if record recNo does not exist
// or is marked deleted
// throws RecordLockedException if the found record is already
// locked 
public void lock(int recNo)
throws RecordNotFoundException, RecordLockedException;
// release the lock on a record.
// throws RecordNotFoundException if record recNo does not exist
// or is marked deleted
// throws RecordNotLockedException if the found record is not
// locked 
public void unlock(int recNo)
throws RecordNotFoundException, RecordNotLockedException;
// determine if a record is currenly locked. returns true if the
// record is locked, false otherwise
// throws RecordNotFoundException if record recNo does not exist
// or is marked deleted
public boolean isLocked(int recNo)
throws RecordNotFoundException;
}
 

What I found weird in the following text is

The exceptions used in this interface must all be created as member classes of the suncertify.data package

suncertify.data, yet the interface is suncertify.db. Is there something wrong here?
Mark
[ September 06, 2002: Message edited by: Mark Spritzler ]

[Tybon Wu]

This is my interface. Notice it's called DBAccess.

package suncertify.db;
public interface DBAccess {
// read an entire record from a given record number
public String [] readRecord(long recNo)
throws RecordNotFoundException;
// attempt to modify the fields of a record.
// throws RecordNotFoundException if record recNo does not exist
// or is marked deleted
// throws RecordLockedException if the record is locked and
// lockCookie does not match the specified cookie
public void updateRecord(long recNo, String [] data,
long lockCookie)
throws RecordNotFoundException, RecordLockedException;
// delete the record, make the record number and associated disk
// storage available for reuse
// throws RecordNotFoundException if record recNo does not exist
// or is already marked deleted
// throws RecordLockedException if the record is locked and
// lockCookie does not match the specified cookie
public void deleteRecord(long recNo, long lockCookie)
throws RecordNotFoundException, RecordLockedException;
// determine the record number that contains a given key. Lock
// the record if lock is true.
// throws RecordNotFoundException if the key cannot be matched
// exactly
// throws RecordLockedException if lock is true, but the found
// record is already locked 
// returns an instance of the nested class DB.Found. This nested
// class serves to carry two return values out of the same
// method. The values are the matching record number, and the
// lock cookie if a lock was requested.  public Found findByKey(String key, boolean lock)
throws RecordNotFoundException, RecordLockedException;
// determine the record numbers that match any non-null element
// of the criteria array.
// null fields are treated as wild cards, and matches are
// performed from the start of the field up to the end of the
// criteria string. For example, Fred matches Fred or Freddy.
// returns all matching record numbers at once. This method
// ignores locks, returning the record numbers regardless.
// throws RecordNotFoundException if nothing matches the criteria
public long [] findByCriteria(String [] criteria)
throws RecordNotFoundException;
// create a new record in the database (possibly reuse a deleted
// entry). Insert the given data, and return the record number
// of the new record.
public long createRecord(String [] data)
throws DuplicateKeyException
// lock a record so that the record is only accessible to this
// client.
// Returned value is a cookie that must be used to unlock the
// record
public long lockRecord(long recNo)
throws RecordNotFoundException, RecordLockedException;
// release the lock on a record. cookie must be the cookie
// returned when the record was locked
public void unlock(long recNo, long cookie)
throws RecordNotFoundException, RecordNotLockedException;
// structure used to allow the locking find method to return two
// results together
public class Found implements java.io.Serializable {
public long recordNumber;
public long lockCookie;
}
}

My interface requires a matching lock cookie to write or unlock the record. Looks like your interface has more freedom in terms of how the access control is implemented. I also have to create the exceptions in the suncertify.data package. I just did what it says and import the exceptions I need.