👀 Views: 178 💬 Answers: 1 📅 Created: 2025-06-02

java completablefuture executorservice exception-handling

I've been banging my head against this for hours... I'm experiencing an issue with handling exceptions thrown within a `CompletableFuture` when using a custom `ExecutorService`. In my application, I have a method that performs asynchronous tasks and returns a `CompletableFuture`. However, when an exception occurs in the task, I'm not able to catch it in the way I expect. Here's a simplified version of my code: ```java import java.util.concurrent.CompletableFuture; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class AsyncExample { private final ExecutorService executorService; public AsyncExample() { this.executorService = Executors.newFixedThreadPool(2); } public CompletableFuture<String> fetchData() { return CompletableFuture.supplyAsync(() -> { throw new RuntimeException("Data fetch failed!"); }, executorService); } public void handleData() { fetchData().handle((result, ex) -> { if (ex != null) { System.out.println("Exception occurred: " + ex.getMessage()); } else { System.out.println("Received data: " + result); } return null; }); } public static void main(String[] args) { AsyncExample example = new AsyncExample(); example.handleData(); example.executorService.shutdown(); } } ``` When I run this code, I see the console output for the exception, but it doesn't appear to propagate as I expect. The exception handling part in `handle` is effectively invoked, but it doesn't seem to affect control flow. I also tried using `exceptionally` instead of `handle`, but it behaves similarly. Is there a best practice for handling exceptions in this context, especially when using a custom `ExecutorService`? Should I configure the `CompletableFuture` differently or handle exceptions in another way to ensure my application behaves as intended? Any guidance or examples would be greatly appreciated! Is there a better approach?