Preventing access of DAO layer from Service layer.

[chets patel]

Hi
I have question regarding DAO design pattern.
Generally we separate service layer from database layer by interface like DAO.
e.g

    public interface xxxDAO {
    public void getData(int id);
}

public class xxxDAOImpl impelements xxxDAO {
     public void getData(int id) {
      // code for retriving data from db.
    }
}

Now I will acccess the DAO class from the service layer as follows.

    
  public class Service {
    public void method() {
      xxxDAO var = new xxxDAOImpl();
      var.getData(id);
   }
}

My question is as all of my DAO classes are public I can even access it from VIEW layer also.
How can I prevent the DAO access from Viwe layer.
Please help. I am very much confused.

[David Newton]

Just don't use them on the view layer. Or don't expose them to the view layer: not knowing what your view layer is makes it harder to help.

[chets patel]

Hi David
Thanks for your fast response..
How can I prevent them from exposing to View layer?

[David Newton]

Depends on the view layer. You may not be able to, if the view layer can instantiate arbitrary classes, at least not without some trickery. Which cannot possibly be worth it in almost all situations. What are you so afraid of that you must absolutely restrict access to your app's classes?

[chets patel]

one solution I found is if I use the Factory design pattern for DAO layer....I can prevent the access to DAO classes...
is that ok?

[David Newton]

How does that prevent access to the DAO classes? Couldn't I just instantiate one in the JSP using a scriptlet or tag?

What *specifically* are you trying to accomplish?