invocation.resolveAnnotation(Timer.class) jumps into org.jboss.aop.joinpoint.MethodInvocation.resolveAnnotation(Class annotation). Here is that method:

public Object resolveAnnotation(Class annotation)
{
1 Object val = super.resolveAnnotation(annotation);
2 if (val != null) return val;
3 if (getAdvisor() != null)
4 {
5 val = getAdvisor().resolveAnnotation(getMethod(), annotation);
6 if (val != null) return val;
7 }
8 return null;
}

Line 1 returns null therefore line 2 does nothing
getAdvisor() in line 3 returns non null so that line 5 is executed
Here is the code for org.jboss.aop.Advisor.resolveAnnotation(Method m, Class annotation):

public Object resolveAnnotation(Method m, Class annotation)
{
01 if (metadataContext != null)
02 {
03 Object val = metadataContext.getAnnotation(m, annotation);
04 if (val != null) return val;
05 }
06
07 if (annotations.isDisabled(m,annotation))
08 return null;
09
10 Object value = annotations.resolveAnnotation(m, annotation);
11 if (value == null) value = AnnotationElement.getVisibleAnnotation(m, annotation);
12 return value;
}

Interesting note: the "annotations" property on the Method object "m" that is passed into this method is null
Line 01 doesn't do anything because the metadataContext is null
Line 07 doesn't do anything because no annotations are "disabled"
Line 10 doesn't do anything because the "annotations" property on "m" is null
Line 11 is interesting. Because I am using JDK 1.5 it doesn't actually invoke AnnotationElement.getVisibleAnnotation(m, annotation). Instead it invokes Method.getAnnotation(Class annotationClass) which tries to get the "declaredAnnotations" list, which is empty, so it does nothing
therefore null is returned to org.jboss.aop.joinpoint.MethodInvocation.resolveAnnotation(Class annotation) which in turn returns null to invocation.resolveAnnotation(Timer.class)