Description Andrew Clement 2008-02-25 16:51:23 EST

There is a need sometimes to determine statically (at weave time) whether an annotation has a particular value.  If it can be determined at weave time rather than using reflection code within the advice, certain scenarios can be optimized.  For example, this trace annotation

enum Level { NONE, LEVEL1, LEVEL2 }
@interface Trace { 
  Level level() default Level.Level1;
}

Without the ability to match on annotation values statically, if we came across this method and advice

@Trace(Level.NONE) public void criticalMethod() {}

before(): execution(@Trace * *(..)) {}

we would have to do reflection in the advice just to discover we shouldn't be tracing.  If that scenario could be matched entirely statically:

before(): execution(@Trace !@Trace(Level.NONE) * *(..)) {}

then we can avoid weaving the criticalMethod() in the first place.