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[aspectj-users] Re: getting 'around' constructor execution
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Gijs, thanks, works like a charm :)
(I thought I attempted something like that, but apparently the
"something like" was not "alike enough" ;) - thanks again)
Danny
Gijs Peek wrote:
Not calling the super constructor is impossible, if A extends some class it
has to call one super constructor or the other.
Now, assuming that you want to call the parameterless super constructor
instead of the constructor with the Type parameter, you can use aspectj to do
that.
You are currently trying to use a constructor execution join point. This join
point, according to The AspectJTM Programming Guide, matches 'When the body
of code for an actual constructor executes, after its this or super
constructor call'. Thus, you cannot use this construction.
You can, however, match constructor call join points, and call another
constructor instead. You can define a new constructor in your aspect. Let me
illustrate this with an example:
public abstract class ASuper {
public ASuper() {
System.out.println("Goodness has occurred");
}
public ASuper(Type t) {
System.out.println("Badness has occurred");
}
}
public class A extends ASuper {
private Type var1;
public A(Type arg) {
super(arg);
System.out.println("1");
var1 = arg;
System.out.println("2");
}
public static void main(String[] args) {
new A(null);
}
}
public privileged aspect AAsp {
pointcut constructorCall(Type arg):
call(A.new(Type))
&& args(arg);
private A.new(Type arg, AAsp a) {
super();
var1 = arg;
}
A around(Type arg): constructorCall(arg) {
System.out.println("advice A constructor");
return new A(arg, this);
}
}
PS pre-initialization and initialization join points won't do you any good
either, they respectively match the code before and after the super call.
cheers,
- Gijs
On Tuesday 18 September 2007 11:12:54 danny wrote:
oops forgot the pointcut declaration :
pointcut constructor(A instance, Type arg):
execution (A.new (Type))
&& this(instance)
&& args(arg);
the class to be woven is something like
public class A {
private Type var1;
public A(Type arg) {
super(arg);
var1=arg;
}
}
the actual goal is to replace the constructor so that 'super(arg)' is
not called.
as before, all help much appreciated.
danny wrote:
the advice -I just want to see if I enter the advice for now- :
A around(A instance, Type arg): constructor(instance, arg) {
System.out.println("advice A constructor");
return instance ();
}
I get the following error when weaving :
[WeavingURLClassLoader] error at.......incompatible return type applying
to constructor-execution(void A.<init>(Type))
I've tried some other constructs, this is the only one I actually
trigger something, all other don't even try to weave :(
What do do ?
All help appreciated
Danny
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