JavaCompletableFuture异常处理全攻略

CompletableFuture future = CompletableFuture
    .supplyAsync(() -> {
        if (true) throw new RuntimeException("Something went wrong");
        return "Hello";
    })
    .exceptionally(ex -> {
        System.out.println("Caught exception: " + ex.getMessage());
        return "Fallback value";
    });

System.out.println(future.join()); // 输出: Fallback value
  

CompletableFuture future = CompletableFuture
    .supplyAsync(() -> {
        return 10 / 0; // 抛出 ArithmeticException
    })
    .handle((result, ex) -> {
        if (ex != null) {
            System.out.println("Error occurred: " + ex.getMessage());
            return "Recovered from error";
        }
        return "Result: " + result;
    });

System.out.println(future.join()); // 输出: Recovered from error
  

CompletableFuture future = CompletableFuture
    .completedFuture("5")
    .thenApply(s -> Integer.parseInt(s))
    .thenApply(num -> num / 0) // 异常在此处抛出
    .exceptionally(ex -> {
        System.out.println("In chain error: " + ex.getCause().getMessage());
        return -1;
    });

System.out.println(future.join()); // 输出: -1
  

CompletableFuture future = CompletableFuture
    .supplyAsync(() -> {
        throw new RuntimeException("Oops!");
    })
    .whenComplete((result, ex) -> {
        if (ex != null) {
            System.out.println("Logging failure: " + ex.getMessage());
        } else {
            System.out.println("Success: " + result);
        }
    })
    .exceptionally(ex -> "Default");

System.out.println(future.join()); // 输出: Default