failsafe: Fallback success and failure policy listeners

Hi,

I’ve a question on using policy listeners with Fallback policy. I understand that onSuccess() is executed when the fallback is executed successfully.

However I’m observing something I didn’t quite expect. For e.g., with the below Fallback policy configured to execute on null result, I would not expect Got from fallback to be printed because the main call returns non-null and so fallback logic itself should not be executed.

        Fallback<String> fallback = Fallback.of("hello")
                .handleResult(null)
                .onSuccess(e -> System.out.println("Got from fallback"))
                .onFailure(e -> System.out.println("Failed to get from fallback"));

        String result = Failsafe.with(fallback)
                .get(() -> "world");

        System.out.println("Result is " + result);

But I get the below output -

Got from fallback
Result is world

Why did the onSuccess() listener get executed?

And if I change the main call to return null, then the onFailure() listener is getting executed even though the fallback executes successfully and returns the fallback value.

        Fallback<String> fallback = Fallback.of("hello")
                .handleResult(null)
                .onSuccess(e -> System.out.println("Got from fallback"))
                .onFailure(e -> System.out.println("Failed to get from fallback"));

        String result = Failsafe.with(fallback)
                .get(() -> null);

        System.out.println("Result is " + result);

Output -

Failed to get from fallback
Result is hello

Perhaps my understanding is incorrect or I’m being daft. 😅