AspectJ advice on method of a class that has a field - aspectj

Question

I want to write an around advice to set a correlation-id into MDC before the invocation of proceed() and return the old value after it. Here is how far I got:
public aspect CorrelationIdAspect
{
private pointcut notPrivateMethod() :
execution(!private * *(..));
private pointcut methodWithContract(Contract contract) :
execution( * *.*(Contract, ..)) && args(contract, ..);
Object around(Contract contract) : methodWithContract(contract) && notPrivateMethod()
{
String oldCorrelationId = MDC.get(Constants.CORRELATION_ID);
try
{
String id = contract.getId().toString();
MDC.put(Constants.CORRELATION_ID, id);
Object result = proceed(contract);
return result;
}
finally
{
MDC.put(Constants.CORRELATION_ID, oldCorrelationId);
}
}
}
Now I want that this advice should only be applied to classes that have a field of type
org.apache.logging.log4j.Logger
because - obviously - a class that has no logger doesn't need to have the correlation id set and restored. Has anybody an idea how that can be accomplished?
Many thanks in advance!

Answer 1

You want to use compiler option -XhasMember (see also my other answer), to be found in Eclipse here:
Then you
add a marker interface to your aspect,
use ITD in order to declare that each class having a static Logger field ought to implement that interface and
match on the marker interface and all its implementing classes:
public aspect CorrelationIdAspect {
// 1. marker interface
private interface HasLogger {}
// 2. use ITD in order to declare that each class having a
// 'static Logger' field ought to implement that interface
declare parents :
hasfield(static Logger *) implements HasLogger;
private pointcut notPrivateMethod() :
execution(!private * *(..));
// 3. match on the marker interface and all its implementing classes
private pointcut hasLogger() :
within(HasLogger+);
private pointcut methodWithContract(Contract contract) :
execution(* *(Contract, ..)) && args(contract, ..);
Object around(Contract contract) :
methodWithContract(contract) && notPrivateMethod() && hasLogger()
{
System.out.println(thisJoinPoint);
return proceed(contract);
}
}