Spring AOP AfterThrowing vs. Around Advice

Question

when trying to implement an Aspect, that is responsible for catching and logging a certain type of error, I initially thought this would be possible using the AfterThrowing advi

Answer 1

Actually, it is possible to catch exception within AfterThrowing advice as well. I know it is a convoluted example, but it works.

@Aspect
@Component
class MyAspect {

    @Autowired
    public Worker worker;

    @Pointcut(value = "execution(public * com.ex*..*.*(..))")
    public void matchingAll(){}

    @AfterThrowing(pointcut = "matchingAll()", throwing = "e")
    public void myAdvice(RuntimeException e){
        Thread.setDefaultUncaughtExceptionHandler((t, e1) -> 
                System.out.println("Caught " + e1.getMessage()));
        System.out.println("Worker returned " + worker.print());
    }
}

@Component
class Worker {

    public static int value = 0;

    public int print() {
        if (value++ == 0) {
            System.out.println("Throwing exception");
            throw new RuntimeException("Hello world");
        } else {
            return value;
        }
    }
}

@SpringBootApplication
@EnableAspectJAutoProxy
public class AdvicesDemo {

    public static void main(String[] args) {
        final ConfigurableApplicationContext applicationContext = SpringApplication.run(AdvicesDemo.class);
        final Worker worker = applicationContext.getBean(Worker.class);
        System.out.println("Worker returned " + worker.print());
        System.out.println("All done");
    }
}

As you can see it is more about how to catch originally thrown exception and thus prevent its propagation back to the caller.

Working example on GitHub (check com.example.advices package)

Answer 2

The Spring reference doc says:

"After throwing advice runs when a matched method execution exits by throwing an exception"

By then it's too late to catch the exception as it has already been thrown and the method has exited. The approach you've taken with the @Around advice is the only way to actually catch the exception and deal with it before the method exits.