如何抽象捕获的异常CompletableFutures以调用方法

Question

Ok, I have methods like

1. CompletableFuture fetchCar(int id);
2. CompletableFuture runSomething(Something t, Extra d);
3. CompletableFuture invoke();

and I would like a single method that I can use that does the following such that it converts any synchronous exceptions to be put in the future

private CompletableFuture<Void> invokeSomething(Something something) {
    CompletableFuture<Void> future;
    try {
        future = something.runSomething(t, d);
    } catch(Throwable e) {
        future = new CompletableFuture<Void>();
        future.completeExceptionally(e);
    }

    return future;
}

Please note that I just happend to pick #2 as the example but I would like to make that generic so I can stop typing that as in general it needs to be done once in a while to ensure you handle synch and asynch exceptions the same.

Answer 1

I'm not sure this is what you're looking for, but you could create a utility function:

public static <T> CompletableFuture<T> foo(Callable<CompletableFuture<T>> callable) {
    try {
        return callable.call();
    } catch (Exception ex) {
        return CompletableFuture.failedFuture(ex);
    }
}

You'd then use it like so:

Something something = ...;
CompletableFuture<Void> future = foo(() -> invokeSomthing(something));

---

Some Notes:

1. Used Callable because its functional method, call , can throw Exception . If something like Supplier was used then using it with methods that can throw checked exceptions would be messy.
2. Used catch (Exception ex) rather than catch (Throwable ex) because Callable#call doesn't throw Throwable and it's usually considered bad practice to catch Error s. You can always change it to Throwable if you want.
3. This utility method will return a failed future, caused by an NPE, if the callable is null ; don't know if that's desired.