Comments on: Exposing collections: paranoia vs trust approaches

By: Khalil

Khalil — Mon, 26 May 2008 22:14:13 +0000

Rather than providing a List getElements() kind of method you would have BGGA style http://www.javac.info

withElements( {Element=>void throws X} closure){
for(Element elt:elements) closure.invoke(element);
}

in client code you would write control invocation syntax
for withElements(Element elt){
System.out.println(elt);
}

By: Aviad

Aviad — Mon, 26 May 2008 19:49:28 +0000

@Khalil: while I agree that closures shine on many fields, I fail to see how they help with this specific case… Can you please elaborate?

By: Khalil

Khalil — Sun, 25 May 2008 12:36:21 +0000

This is an area where closures shine, they preserve encapsulation and would save memory, of course they don’t solve the issue with frameworks that need to muck with your collection

By: Aviad

Aviad — Thu, 22 May 2008 03:15:37 +0000

@Adrian: I actually like your approach better than James’, as it allows me to have the collection contained in some other support class (see my answer to James)

Still, I think it breaks encapsulation, and makes it harder to unit-test the code, as it would be impossible to test the “setCollection” method, it being private.

By: Adrian Smith

Adrian Smith — Wed, 21 May 2008 16:05:11 +0000

@James – Nice one, I hadn’t thought of doing that.

What I always do, to implement the paranoia approach with Hibernate, is to create “private” getters and setters for the actual List or whatever. That way noone can call them, but it works just fine with Hibernate. Then create other methods addItem or whatever, that I want other people to call.

By: Aviad

Aviad — Tue, 20 May 2008 19:05:30 +0000

@All: I’m sorry about the connection problems… I should really switch the current hosting plan to a better one.

@Paul: You’re right, but that still doesn’t give you the access required to write to the fields…

By: Paul

Paul — Tue, 20 May 2008 18:31:44 +0000

First comment gave me a connection error so sorry if this is a duplicate. The reflection api gives access to a classes private members via the getDeclaredFields method:

http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Class.html#getDeclaredFields()

… “This includes public, protected, default (package) access, and private fields,…”

By: Aviad

Aviad — Tue, 20 May 2008 17:27:19 +0000

@Brian: You’re right – but as I remember, and correct me if I’m wrong, it also requires special permissions (a specific flag in ReflectPermission?)

By: Brian Duff

Brian Duff — Tue, 20 May 2008 16:05:37 +0000

It probably uses the setAccessible() method on java.lang.reflect.Field. If you make a field accessible, you can set it using reflection even if it’s private. Breaks encapsulation for sure, but a useful trick for injection frameworks.

By: Adrian Smith

Adrian Smith — Tue, 20 May 2008 14:51:50 +0000

http://www.databasesandlife.com/encapsulation-or-public-attributes-but-nothing-inbetween/

(Oh if only things like pingback and trackback would just work!)