Java 17: scenarios Handling in CompletableFuture with Nested Callbacks - implementing handling Propagation
I'm working with an scenario with handling exceptions in a nested `CompletableFuture` setup in Java 17. When an exception is thrown in the inner callback, it seems to be swallowed, and I'm not able to propagate the behavior properly. Here's the structure I'm using: ```java CompletableFuture.supplyAsync(() -> { // Some long-running task return "Result"; }).thenApply(result -> { return CompletableFuture.supplyAsync(() -> { // Simulate an behavior if (result.equals("Result")) { throw new RuntimeException("Inner exception"); } return "Processed " + result; }); }).handle((res, ex) -> { if (ex != null) { System.out.println("behavior occurred: " + ex.getMessage()); return "Fallback Result"; } return res; }).join(); ``` The output I get when running this code is `behavior occurred: null`, which is misleading since the exception is happening in the inner `supplyAsync`. I've tried wrapping the inner `supplyAsync` in a try-catch block but that didn't seem to work either. What is the correct way to handle exceptions in such a nested `CompletableFuture` scenario? Ideally, I want to catch the exception from the inner future and have it propagate to the outer handler without losing the original stack trace.