Vertx / RxJava / WebClient / ApiGateway / Reactive

Question

我正在使用vert.x和RxJava在Apigateway上工作。我想发送2个Api的响应请求，从两个请求中获取响应，然后通过HttpServer发送组合的JSON。但是onComplete()会提早执行并返回空JSON。我认为问题是由vert.x的asynchronous字符引起的，但我不完全是怎么回事。

这是我的方法：

private void dispatchBoth(RoutingContext routingContext) {

    Observer<String> observer = new Observer<String>() {

        JsonArray jsonArray = new JsonArray();

        @Override
        public void onSubscribe(Disposable disposable) {
            System.out.println("Start");

        }

        @Override
        public void onNext(String s) {
            Thread t = new Thread(() -> {
                if(s=="/api/userApi/selectAllUsers") {

                        WebClient client = WebClient.create(vertx);
                            client
                                .get(8081, "localhost", s)
                                .send(ar->{
                                    if (ar.succeeded()) {
                                        HttpResponse<Buffer> response = ar.result();

                                        jsonArray.addAll(response.bodyAsJsonArray());
                                        System.out.println(jsonArray.encodePrettily());

                                    } else {
                                        System.out.println("Something went wrong " + ar.cause().getMessage());
                                    }
                                });

                }else if(s=="/api/holidayApi/selectAllHolidays") {
                        WebClient client = WebClient.create(vertx);
                        client
                                .get(8080, "localhost", s)
                                .send(ar -> {

                                    if (ar.succeeded()) {

                                        HttpResponse<Buffer> response = ar.result();

                                        jsonArray.addAll(response.bodyAsJsonArray());
                                       //  System.out.println(jsonArray.encodePrettily());

                                    } else {
                                        System.out.println("Something went wrong " + ar.cause().getMessage());
                                    }
                                });
                    }
                });
                t.start();
        }
        @Override
        public void onError(Throwable throwable) {

        }

        @Override
        public void onComplete() {
                System.out.println(jsonArray.encodePrettily());
                routingContext.response().end(jsonArray.encodePrettily());
        }
    };
    Observable.fromArray(com).subscribe(observer);
}

这就是我在控制台上得到的输出：

[ ]
[ {
  "holidayId" : 2,
  "userId" : 3,
  "place" : "Poland",
  "date" : {
    "year" : 2016,
    "month" : "DECEMBER",
    "dayOfMonth" : 29,
    "dayOfWeek" : "THURSDAY",
    "era" : "CE",
    "dayOfYear" : 364,
    "leapYear" : true,
    "monthValue" : 12,
    "chronology" : {
      "id" : "ISO",
      "calendarType" : "iso8601"
    }
  }
}, {
  "holidayId" : 10,
  "userId" : 1,
  "place" : "Netherland",
  "date" : {
    "year" : 2020,
    "month" : "JANUARY",
    "dayOfMonth" : 21,
    "dayOfWeek" : "TUESDAY",
    "era" : "CE",
    "dayOfYear" : 21,
    "leapYear" : true,
    "monthValue" : 1,
    "chronology" : {
      "id" : "ISO",
      "calendarType" : "iso8601"
    }
  }
}, {
  "userId" : 1,
  "name" : "Kacper",
  "phone_number" : "667667202"
}, {
  "userId" : 3,
  "name" : "Kamil",
  "phone_number" : "6734583443"
}, {
  "userId" : 4,
  "name" : "Janek",
  "phone_number" : "231253575"
}, {
  "userId" : 5,
  "name" : "Grzegorz",
  "phone_number" : "123456789"
}, {
  "userId" : 6,
  "name" : "Justin",
  "phone_number" : "111000111"
}, {
  "userId" : 8,
  "name" : "Mike",
  "phone_number" : "997"
}, {
  "userId" : 9,
  "name" : "Gorge",
  "phone_number" : "991"
} ]

Answer 1

我看到您正在onNext()中启动新线程？当您使用Thread.start()启动新线程时，它将并行进行其工作，当前Observable.onNext()将认为工作已完成。这将导致调用onComplete()。

没有人等待线程的工作完成。希望你明白我的意思。

现在，我对vert.x不熟悉，但是按照RxJava的方式，似乎不需要使用Thread。您可以删除它，并将其余的逻辑直接保留在onNext()方法中。

Answer 2

onComplete准时执行：当字符串的输入流完成时。您需要另一种方法来等待所有I / O操作完成。这是一个棘手的部分，我不知道Vertx或RxJava是否可以做到这一点，但是标准Java API可以使用CompletableFuture。因此，我们创建了从CompletableFuture到Handler的适配器，该适配器保存一个I / O操作的结果：

class HandelerFuture extends CompletableFuture<JsonArray> 
         implements Handler<AsyncResult<HttpResponse<Buffer>>> {
    @Override
    public void handle(AsyncResult<HttpResponse<Buffer>> ar) {
        if (ar.succeeded()) {
            JsonArray array = ar.result().bodyAsJsonArray();
            super.complete(array);
        } else {
            super.completeExceptionally(ar.cause());
        }
    }
}

此外，您无需将onNext方法的主体包装在Tread中。其次，您无需检查传递的url字符串，因为它没有任何区别。第三，您仅使用Observer来处理url字符串列表-这太复杂了。普通循环就足够了。

CompletableFuture<HandelerFuture[]> dispatchBoth(String... urls) {
    ArrayList<HandelerFuture> futures = new ArrayList<>(); // all results
    for (String url : urls) {
        HandelerFuture future = new HandelerFuture();
        futures.add(future);
        WebClient client = WebClient.create(vertx);
        client.get(8081, "localhost", url)
              .send(future);
    }
    CompletableFuture all = new CompletableFuture();
    HandelerFuture[] array = futures.toArray(new HandelerFuture[0]);
    CompletableFuture.allOf(array)
            .thenRunAsync(() -> all.complete(array));
    return all;
}

然后可以如下运行：

    CompletableFuture<HandelerFuture[]> future = dispatchBoth(com);
    HandelerFuture[] results = future.get();
    JsonArray finalArray;
    for (HandelerFuture result:results) {
        try {
            // extract partial json array
            JsonArray partialArray = result.get();
            // combine partialArray with finalArray somehow
        } catch (Exception e) {
            // this is the exception got in handle() method as ar.cause().
            e.printStackTrace();
        }
    }
    routingContext.response().end(finalArray.encodePrettily());

您没有告诉您如何组合json数组，所以我没有实现它。