HttpClient.sendAsync metodu - HttpClient API

Giriş

GET veya POST için yaratılan HttpRequest nesnesini asenkron olarak gönderir. Metodun imzası şöyle

public abstract <T> CompletableFuture<HttpResponse<T>> sendAsync​(
  HttpRequest request,
  HttpResponse.BodyHandler<T> responseBodyHandler)

Cancel

Açıklaması şöyle. Java 16'dan sonra CompletableFuture.cancel() ile iptal ediliyor.

Since Java 16 it is possible to cancel a request by interrupting the thread that called HttpClient::send or by invoking cancel(true) on the CompletableFuture returned by HttpClient::sendAsync. 

Örnek

Şöyle yaparız

val client = HttpClient.newHttpClient()
log.info("Sending ...")
val f = client.sendAsync(
    HttpRequest
      .newBuilder(new URI("http://localhost:8080/stream"))
      .GET()
      .version(HttpClient.Version.HTTP_1_1)
      .build(),
    BodyHandlers.ofString()
  )
log.info("Sent ...")
Thread.sleep(1000)
f.cancel(true) // java 11: no effect; java 20: works

sendAsync metodu

Örnek

Şöyle yaparız

HttpRequest request = ...;
client.sendAsync(request, BodyHandlers.ofString())
      .thenApply(HttpResponse::body)
      .thenAccept(System.out::println)
      .join();

Örnek

Şöyle yaparız

static <T> CompletableFuture<List<T>> fetchAsync(String url) {
  // create a client
  var client = HttpClient.newHttpClient();
  // create a request
  var request = HttpRequest
    .newBuilder(URI.create(url))
    .header("accept", "application/json")
    .build();
  // use the client to send the request
  final var response = client
    .sendAsync(request, BodyHandlers.ofString())
    .thenApply(HttpResponse::body)
    .thenApply(App::<T>parseJSON);
  // the response:
  return response;
}

parseJSON şöyledir

private static <T> List<T> parseJSON(String textResponse) {
  final ObjectMapper objectMapper = new ObjectMapper();
  List<T> objects = new ArrayList<>();
  try {
    objects = objectMapper.readValue(textResponse, new TypeReference<List<T>>() {});
  } catch (JsonMappingException | JsonProcessingException e) {
    ...
  }
  return objects;
}

İki tane isteği paralel çalıştırmak için şöyle yaparız

CompletableFuture<List<Book>> booksFuture = fetchAsync(
  "https://[your-api-here]/api/books"
);
CompletableFuture<List<Author>> authorsFuture = fetchAsync(
  "https://[your-api-here]/api/authors"
);
booksFuture.get();
authorsFuture.get();