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the read() method

Julio Cesar Marques
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Joined: Mar 21, 2009
Posts: 67
Hi guys!

in DBMain i have to implement the method:
public String[] read(int recNo) throws RecordNotFoundException;
but it expects a int recNo. How i can get this value?
In File Description don't have a field named idRec. What do i?


Julio Cesar Lopes Marques
Sun Certified Java Developer 5, Sun Certified Java Programmer 5
Roberto Perillo
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Joined: Dec 28, 2007
Posts: 2267
    
    3

The "recNo" is the record's primary key. You can use the position of the record in the database file


Cheers, Bob "John Lennon" Perillo
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Julio Cesar Marques
Ranch Hand

Joined: Mar 21, 2009
Posts: 67
hmmm ok.
One more thing i need to use headers and schema from db file to recovery data or i can jump to data section (pos 71 in my case) directly and slice parts to get data? I think that using the entire file is the right, but i think i don't need write a generic .db file reader but a db-2x1.db reader in this case i'll lost my time parsing headers and schema.
Roberto Perillo
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Joined: Dec 28, 2007
Posts: 2267
    
    3

You can decide that. For instance, you can decide to read the db schema "on the fly", or you can hardcode it. I myself hardcoded it. I know others created a way to read it dynamically. Just remember to justify your decision in the end!
Roel De Nijs
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Joined: Jul 19, 2004
Posts: 5545
    
  13

I'm one of those that created a way to read it dynamically and that's not that hard. main advantage of this approach: you could use the data-class for other files having a similar data-structure but of course this isn't a requirement for the assignment, so you don't have to do it.

whatever you choose, justify in choices.txt because for many things there is no right or wrong if you have a valid argumentation for doing it that particular way


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Julio Cesar Marques
Ranch Hand

Joined: Mar 21, 2009
Posts: 67
Hi Roel!

I'm never think by this point of view, maybe have one robust class able to understand *.db is not too bad!

[]'s
Roel De Nijs
Bartender

Joined: Jul 19, 2004
Posts: 5545
    
  13

if you have a dynamic db-schema you can handle e.g. changes in field lengths without changing your data-class (if header info is updated appropriately of course). you could even handle a file where a column is added or removed without altering your Data-class (the business logic should be changed of course)
 
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