我有这种奇怪的类型CompletableFuture< CompletableFuture< byte []>>但我想要CompletableFuture< byte []>.这可能吗？
public Future<byte[]> convert(byte[] htmlBytes) {
PhantomPdfMessage htmlMessage = new PhantomPdfMessage();
htmlMessage.setId(UUID.randomUUID());
htmlMessage.setTimestamp(new Date());
htmlMessage.setEncodedContent(Base64.getEncoder().encodeToString(htmlBytes));
CompletableFuture<CompletableFuture<byte[]>> thenApply = CompletableFuture.supplyAsync(this::getPhantom,threadPool).thenApply(
worker -> worker.convert(htmlMessage).thenApply(
pdfMessage -> Base64.getDecoder().decode(pdfMessage.getEncodedContent())
)
);
}
解决方法
其文档中有一个
bug,但
CompletableFuture#thenCompose系列方法相当于flatMap.它的声明也应该给你一些线索
public <U> CompletableFuture<U> thenCompose(Function<? super T,? extends CompletionStage<U>> fn)
thenCompose获取接收者CompletableFuture的结果(称之为1)并将其传递给您提供的函数,该函数必须返回自己的CompletableFuture(称之为2). ThenCompose返回的CompletableFuture(称之为3)将在2完成时完成.
在你的例子中
CompletableFuture<Worker> one = CompletableFuture.supplyAsync(this::getPhantom,threadPool); CompletableFuture<PdfMessage /* whatever */> two = one.thenCompose(worker -> worker.convert(htmlMessage)); CompletableFuture<byte[]> result = two.thenApply(pdfMessage -> Base64.getDecoder().decode(pdfMessage.getEncodedContent()));
