Seam promote bad design?

[guanwh]

I know it is a small problem, but when i go through the seam document (all documents,articles in the internet), I found all the action code actually has mixed responsibility: page navigation and business logic. See the following code from book demo:
@Stateless (1)
@Name("register")
public class RegisterAction implements Register
{

@In (2)
private User user;

@PersistenceContext (3)
private EntityManager em;

@Logger (4)
private Log log;

public String register() (5)
{
List existing = em.createQuery("select username from User where username=:username")
.setParameter("username", user.getUsername())
.getResultList();

if (existing.size()==0)
{
em.persist(user);
log.info("Registered new user #{user.username}"); (6)
return "/registered.jsp"; (7)
}
else
{
FacesMessages.instance().add("User #{user.username} already exists"); (8)
return null;
}
}

}

the register function actually has dual resonsibility which broke a fundametal OO design principle:Single-Resonsibility-Principle. and all the generated seam code is same.

Would it be better that an official tutorial providing better sample code?

No offense. I do like SEAM.

Thanks

[pbakker]

To my opinion this is a pretty standard way of using JSF, so it's quite logical to map the same examples to Seam.
I do agree that it's not the best seperation of concerns, but on the other hand it works pretty well like this.
Specially for smaller applications I see no good reasons to do differently.

[pmuir]

You can provide more separation by returning a logical outcome from the action method and mapping that to a view from a naviation rule in faces-config.xml. IMO this provides the necessary split between business logic and navigation.

I guess the Seam examples return view-ids directly as it makes the example more readable (one less place to look).

[evdelst]

I use pageflows for the navigation, the beans don't contain any navigation and I call the action methods using expressions in the flow.
In the views, the buttons return the transitions to use.
It is a pretty clean seperation I think.

[ellenzhao]

Seam + jpdl pageflow really separate concerns very cleanly. You may want to have a look at the number guess example. There's pure business logic in the action class. Another example is DVD store, the newuser flow and the checkout flow.

[guanwh]

"ellenzhao" wrote:
Seam + jpdl pageflow really separate concerns very cleanly. You may want to have a look at the number guess example. There's pure business logic in the action class. Another example is DVD store, the newuser flow and the checkout flow.

Thanks, I will look at the examples you mentioned. Another newbie question, can the statefull action or stateless action's interface be remote, so that all the ejb module located on a separate physical machine? does anyone manage to do this?