java 完整的 future 和异常链

Question

我有以下代码

    return future.exceptionally(t -> {
        if(t instanceof NotFoundException)
            return processNotFound(responseCb, requestCtx, (NotFoundException) t, errorRoutes, null);

        throw new CompletionException(t.getMessage(), t);
        //in scala we would return new CompletableFuture.completeExceptionally(t) and not throw
    });

其中 processNotFound 也返回一个可能失败的 CompletableFuture。

基本上就是这些步骤1.点击主系统2.捕获异常进行恢复3.返回可能失败或成功的恢复的 future

我知道如何在 scala 中执行此操作，但不确定如何在 java 中执行此操作。有人知道吗？

Answer 1

好吧，我想出了自己的解决方案，这是一个黑客

public static <T> ExceptionOrResult<T> convert(Throwable t, T res) {
    return new ExceptionOrResult<T>(t, res);
}

/**
 * This sucks as I could not find a way to compose failures in java(in scala they have a function for this)
 */
public static <T> CompletableFuture<T> composeFailure(CompletableFuture<T> future, Function<Throwable, CompletableFuture<T>> exceptionally) {
    return future.handle((r, t) -> convert(t, r)).thenCompose((r) -> {
        if(r.getException() == null)
            return CompletableFuture.completedFuture(r.getResult());
        return exceptionally.apply(r.getException());
    });
}