Custom Scenario requiring table Lock - Please Suggest

Question

Hi ,
Custom usecase :
There exist a table with following column :
FileName, LastUpdatedBy, ApprovedBy, DisapprovedBy, LogicallyDeleted, FileDescription, Col2
Primary Key - ( FileName, LastUpdatedBy,ApprovedBy)
Constraint : FileName,lastUpdatedBy,ApprovedBy cannot be null. Default values for LastUpdatedBy, ApprovedBy, DisapprovedBy is NONE, and LogicallyDeleted is N.
Note : User should not be allowed to create more that two records for same fileName.
Edit functionality required on UI : On editing a record, a copy of the row should be created with same fileName , LastUpdatedBy with userId of logged in User.
How should I restrict user from doing the following :
Two users open the UI. Selected same record to edit. At time of commit only record for one should get commited, while for other it should not happen as 2 records gets created for same file name as soon as commit is done for one user.
Do i need to have table lock, then count row with a particular file name and if count >2 then commit else throw some exception. And if this is needs to be done than which method should be overridden to do that.
Thanks,
Rajdeep

Answer 1

Hi
To Shay : ( You can define a new method validation at the entity level to do the check for you. http://docs.oracle.com/cd/E16162_01/web.1112/e16182/bcvalidation.htm#CACGFEDC )
From my post : - Where should that logic can be implemented in ADF BC and what logic ( anything different from what I mentioned in post ) ?
If I am going to write validation in custom method at entity level, I think it is not handling the scenario properly. For example : Query for Count on fileName records is fired in validator method for two entities before the commit is happening for any of the two.
Also What logic : do you agree with table lock logic requirement here ?
To Santosh,
I think you didn't got the scenario. It does not talk about two user doing normal edit on same record. Notice two facts mentioned in post :
1. When a user selects a record to edit... he is not actually editing it. We create a copy of the row ( with FileName , LastUpdatedBy,ApprovedBy,LogicallyDeleted as readOnly and prepopulated with sameFileName as original record, UserId in LastUpdatedBy, NONE defaults for Approved by and Disapproved By , N default for LogicallyDeleted) launched in popup. Popup has two buttons ... save and cancel. On cancel we rollback transaction ( i.e. deletes the newly created copy ) and Save ... eventually commits the row.
2. Not more two records should get created in table for same fileName. So two users trying to edit same record will eventually try to create the 3 records in database table. It should fail for 3rd one...
What logic should be written ... Does it really need the table lock ? Etc
Thanks,
Rajdeep