In the first case, the generated compare method is a generics bridge method - which merely acts as a bridge from the (Object,Object) variant to your (String,String). If you look at the bytecode for it, you will see it calls the other compare method.
AspectJ does not advise bridge methods, because they just delegate to the 'real' method. If we did then in this case your advice would run twice if you called the Object,Object version.
In your second case you provided your own compare(Object,Object) method and so it was advised.
cheers,
Andy.
2008/9/3 Alex Villazon
<alex.villazon@xxxxxxxxxxx>
Dear all,
I have a problem with the following aspect which can advice methods, depending on how it's compiled...
public class A implements java.util.Comparator <String> {
public int compare(String a, String b) {
return 0;
}
}
javac generated a compare(Object, Object) method corresponding to
public int compare(Object a, Object b) {
return compare((String)a, (String)b);
}
When weaving A.java with the following aspect, only the compare(String, String) method is adviced...
public aspect Foo {
before() : execution(* *(..)) && !within(Foo) {}
}
javac A.java
jar cvf a.jar A.class
ajc -showWeaveInfo -inpath a.jar -outjar woven.jar Foo.aj
Join point 'method-execution(int A.compare(java.lang.String, java.lang.String))' in Type 'A' (A.java:3) advised by before advice from 'Foo' (Foo.aj:2)
Now, if I add the compare(Object, Object) manually, the Foo aspect advice both compare(String, String) and compare(Object, Object) methods!!!!
public class A implements java.util.Comparator /*<String> */ {
public int compare(String a, String b) {
return 0;
}
public int compare(Object a, Object b) {
return compare((String)a, (String)b);
}
}
javac A.java
jar cvf a.jar A.class
ajc -showWeaveInfo -inpath a.jar -outjar woven.jar Foo.aj
Join point 'method-execution(int A.compare(java.lang.String, java.lang.String))' in Type 'A' (A.java:3) advised by before advice from 'Foo' (Foo.aj:2)
Join point 'method-execution(int A.compare(java.lang.Object, java.lang.Object))' in Type 'A' (A.java:6) advised by before advice from 'Foo' (Foo.aj:2)
Curiously, the bytecode for compare(Object, Object) is strictly the same.. in both cases..
public int compare(java.lang.Object, java.lang.Object);
Signature: (Ljava/lang/Object;Ljava/lang/Object;)I
Code:
Stack=3, Locals=3, Args_size=3
0: aload_0
1: aload_1
2: checkcast #2; //class java/lang/String
5: aload_2
6: checkcast #2; //class java/lang/String
9: invokevirtual #3; //Method compare:(Ljava/lang/String;Ljava/lang/String;)I
12: ireturn
LineNumberTable:
line 1: 0
Is this a bug of ajc? I tested it with 1.6.1 and 1.6.2 (development version)
Thanks a lot,
Alex
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