java - 如何在 Spring Boot 中使用 CompletableFuture 并行调用多个方法

Question

我在 Spring Boot 中有一个 Web 服务，它需要向外部 Web 服务发出请求以检索多个货币对的实时汇率。

目前调用外部API的方法是这样的；

@Async
    public CompletableFuture<Double> getBaseRateForCurrencyPair(String sourceCurrency, String targetCurrency) {
        String key = sourceCurrency.toUpperCase() + targetCurrency.toUpperCase();

        Double baseRate = 0.00;

            String baseRateProviderUrl = "https://apilayer.net/api/live?access_key=" + currencyLayerAccessKey + "&source=" + sourceCurrency + "&currencies=" + targetCurrency;
            HttpClientRequest clientRequest = new HttpClientRequest(baseRateProviderUrl);

            try {
                Response response = clientRequest.get();
                String responseStr = response.body().string();

                JSONObject jsonObject = new JSONObject(responseStr);
                baseRate = AppHelper.round(jsonObject.getJSONObject("quotes").getDouble(key), 2);
            } catch (Exception e) {
                e.printStackTrace();
            }

        return CompletableFuture.completedFuture(baseRate);
    }

我想做的是根据我们需要获取汇率的货币对数量，未知次数地调用此方法，等待所有货币对完成并存储结果，准备在 API 中返回响应。

我有一个方法可以接收源货币代码和目标货币汇率列表。

public RateResponse getLiveRates(String sourceCurrency, String[] targetCurrencies) {
        RateResponse rateResponse = new RateResponse();

        rateResponse.setSourceCurrency(sourceCurrency);

        /* Loop through target currencies and start a thread for each */
        Map<String, CompletableFuture<Double>> ratesMap = new HashMap<>();
        for (String targetCurrency : targetCurrencies) {
            ratesMap.put(targetCurrency, matrixHelper.getBaseRateForCurrencyPair(sourceCurrency, targetCurrency));
        }

        /* At this point, I would loop through the Map and grab the results, but only when all are finished */

        return rateResponse;
    }

我的问题是，我无法弄清楚如何等到所有异步调用完成后再开始遍历 Map 并检索结果。

Answer 1

你试过了吗CompletableFuture方法 allOf(CompletableFuture<?>... cfs) ？查找文档 here