How can I have a generic doOnError after exception class specific ones in Reactor

Question

It feels like this should be simple, so I might be missing something obvious. I have a simple example case where I have an error Mono, and I would like to have exception class specific handling with a generic handler.

    Mono.error(new RuntimeException())
            .doOnError(RuntimeException.class, e -> System.out.println("Caught RuntimeException"))
            .doOnError(Throwable.class, e -> System.out.println("Caught Throwable"))
            .block();

output: Caught RuntimeException
        Caught Throwable

The problem is that both consumers will get called (the one with RuntimeException and the generic one with Throwable). Is there a (clean) way to avoid calling the generic one if a more specific one was already called?

Answer 1

If there is a way to recover from an error, use onErrorResume function instead.

Mono.error(new RuntimeException())
    .flatMap(k -> callExternalService(k)
        .onErrorResume(RuntimeException.class, this::recoverFromRuntimeExeption)
        .onErrorResume(Throwable.class, this::recoverFromThrowable)
    );

This way you'll change the execution path of your Mono from error to success and subsequent doOnError won't be called.