Hello, Muhammad!
On Sat, 28 Sep 2013 07:37:37 -0300, Muhammad Gelbana <m.gelb...@gmail.com>
wrote:
The last paragraph on that
page<http://tapestry.apache.org/service-advisors.html>,
states the following:
*If you do, decoration take precedence; all decorators will be in effect
before any advice (internally, they are two separate steps, with advice
being processed and the result of that used by the decorators).*
At first, it states that decoration take precedence, then it states that
internally, the advice is applied and the results is passed to the
decorator.
Is this paragraph contradicting it self ?
It's a hard to understand paragraph, maybe because the concept itself is a
little hard to understand at first. When I first read it, I thought there
was a contradiction, but then I thought again, a light bulb appeared over
my head and I realized it does make sense.
If you have a decorator D and an advice A on service D on method m (not
tested):
public interface S {
int a(int parameter);
}
public class Implementation implements S {
public int m(int parameter) {
System.out.println("S.m: " + parameter);
return parameter;
}
}
public class D implements S {
final private S delegate;
public D(S delegate) {
this.delegate = delegate;
}
public int m(int parameter) {
System.out.println("D.m");
int result = delegate.m(parameter);
System.out.println("D.m: result: " + result);
}
}
public class Advice implements MethodAdvice {
public void advice(MethodInvocation invocation) {
System.out.println("A.m");
// calls the advised method
invocation.proceed();
// let's change the result value
int result = invocation.getReturnValue();
System.out.println("A.m: result:" + result);
invocation.setReturnValue(result * 2);
}
}
If we call S.a(1), the output would be this:
D.m
A.m
S.m: 1
A.m: result: 1
D.m: result: 2
The key concept here is that both service decoration and advice allow you
to add code *both* before *and* after the decorated or advised original
method. So the decorator takes precedence and its code is run before the
advice *and* after the advice.
--
Thiago H. de Paula Figueiredo
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscr...@tapestry.apache.org
For additional commands, e-mail: users-h...@tapestry.apache.org
