CompletableFuture：whenCompleteAsync() 不允许我重新抛出异常

Question

我是 CompletableFuture 的新手。我正在尝试进行一些负面测试，以允许我故意抛出异常的方式。此异常将决定 PASS/FAIL.

这是代码片段：

    protected CompletableFuture<Response> executeAsync(@NonNull Supplier<Response> call) {
        return CompletableFuture
                .supplyAsync(call::get)
                .whenCompleteAsync((response, exception) -> {
                    if (exception == null) {
                        try {
                            Helper.throwIfNotExpected(clientProperties.getName(), response, null);
                        } catch (ServiceException e) {
                            throw new ServiceException(null,e.getMessage(),null);
                        }
                    } else {
                        log.error("Async API call failed.", exception);
                    }
                });
    }

这给我一个错误，在 catch 部分显示 未处理的异常。我查阅了示例和文档，但在 supplyAsync/whenCompleteAsync 中找不到有关异常处理的太多信息。提前致谢。

Answer 1

解决 CompletableFuture 关于检查异常的缺点的一个好方法是委托给另一个 CompletableFuture 实例。对于您的示例，它看起来像

protected CompletableFuture<Response> executeAsync(Supplier<Response> call) {
    CompletableFuture<Response> delegate = new CompletableFuture<>();

    CompletableFuture
        .supplyAsync(call)
        .whenCompleteAsync((response, exception) -> {
            if (exception == null) {
                try {
                    Helper.throwIfNotExpected(clientProperties.getName(), response, null);
                    delegate.complete(response);
                } catch (ServiceException e) {
                    delegate.completeExceptionally(new ServiceException(null,e.getMessage(),null));
                }
            } else {
                log.error("Async API call failed.", exception);
                delegate.completeExceptionally(exception);
            }
        });

    return delegate;
}

CompletableFuture：whenCompleteAsync() 不允许我重新抛出异常

CompletableFuture: whenCompleteAsync() does not let me re-throw an Exception

java

asynchronous

exception

completable-future