Re: DAO design pattern

Lim

Create an interface which defines the data related operations 
independantly of any particular representation/access method (i.e., 
file/JDBC, etc)

public interface SomeObjectDAO {

        public void create(SomeObject object)
                throws DAOException;

        public void delete(Integer objectID)
                throws DAOException;

        public SomeObject findByID(Integer objectID)
                throws DAOException;

        public List findByKeyword(String keyword)
                throws DAOException;
}

Then write an implementation of this interface using the JT/400 API:

public class JT400SomeObjectDAO {

        public SomeObject findByID(Integer objectID) {
 
                AS400File file = ....

                SomeObject someObject = new someObject();

                someObject.setFoo(file.readInteger());
 
                return someObject;
        }

        // ...
}

And finally write a factory to create instances of SomeObjectDAO:

public class SomeObjectDAOFactory {

        private static instance = new SomeObjectDAOFactory();

        public static SomeObjectDAOFactory getInstance() {
                return instance;
        }

        public SomeObjectDAO newInstance() {
                return new JT400SomeObjectDAO();
        }

}

You don't gave to use checked exceptions.   A framework like spring can 
obviate the need for trivial factory objects.




"Lim Hock-Chai" <Lim.Hock-Chai@xxxxxxxxxxxxxxx> 
Sent by: java400-l-bounces+niall.smart=friendsfirst.ie@xxxxxxxxxxxx
03/01/2005 18:40
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Subject
DAO design pattern






Anybody has a good example on how should I design my web application for 
any file access related transaction?
 
I'm using struts to create this web apps.  I just wonder when I'm in the 
Action Form and I need to do some edit/insert/update on a record in a 
file, what is the correct way to design this.  I've read some article 
about DAO design pattern.  If this is a good approach, can anybody provide 
some example.  (Note: I'm using Tomcat4.1 and plan to use DBCP for 
connection pooling.) 
 
thanks.
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