What is the best practice to avoid

sjhyam · **Joined:** Fri Jun 01, 2007 12:41 pm **Posts:** 121

We have a Customer bean as:

Code:

public class Customer{
  private Set roles = new HashSet();
  public Set getRoles() { return roles;}
}

In business controller,

Code:

Customer c = ...//getCustomer() from database
Set roles = c.getRoles(); //this works fine
Set roles = (Set)c.getRoles(); //this works fine
Set roles = (HashSet)c.getRoles(); //throws an exception java.lang.ClassCastException: org.hibernate.collection.PersistentSet

What is the best practice If I want pass Set roles to UI layer as HashSet. My two options are:

a. return getRoles as HashSet in Customer class

Code:

public class Customer{
  private Set roles = new HashSet();
  public Set getRoles() { return new HashSet(roles);}
}

b. Return a new HashSet for c.getRoles() wherever required.

Code:

Set roles = new HashSet(c.getRoles());

I don't want to call c.getRoles() as it is from UI layer as it returns implementation of org.hibernate.collection.PersistentSet and I have to include hibernate.jar in UI layer.

Let me know the best practice.

gonzao_diaz · **Joined:** Mon Nov 26, 2007 2:29 pm **Posts:** 443

Both look bad to me, but the least bad would be b).

However: why do you need to use a concrete implementation (HashSet) at all as a left-side member in your code?
That suggests me you want to directly manipulate that hashSet somehow, and I would strongly advice you against that.
Hibernate, for the most part, doesn't know what you do to that hashSet once you "disconnected" it from its parent object!

I hate providing one of those smug answers that divert your question instead of answer it specifically, but I really advise you to consider

1) why you need such "disconnected" collection at all
2) If you really have to use it, why does it need to be a concrete implementation, instead of just a Set.