CompletableFuture thenAccept 不起作用

Question

欢迎，我很困惑为什么这部分代码不起作用。

public class Main {
public static void main(String[] args) throws URISyntaxException {
    final String URL = "https://jsonplaceholder.typicode.com/users/1";

    HttpRequest request = HttpRequest.newBuilder(new URI(URL)).GET().timeout(Duration.of(10, ChronoUnit.SECONDS)).build();

    HttpClient.newHttpClient().sendAsync(request, HttpResponse.BodyHandlers.ofString()).thenAcceptAsync(r -> {
        System.out.println(r.statusCode());
        System.out.println(Thread.currentThread().getName());
    }, Executors.newFixedThreadPool(10));

    
    System.out.println("END OF PROGRAM");
}

}

结果是：

END OF PROGRAM

如果我提供了 ExecutorService JVM 应该等待 CompletableFuture 完成（.thenAceptAsync 部分）但程序立即完成。

大概是我的心态错了。 有人可以解释一下吗？

Answer 1

程序在请求完成之前退出。 该请求使用sendAsync异步执行，因此它不会阻止程序的执行。

要阻止执行并等待 API 响应，您必须使用response.get(); 如下：

public static void main(String[] args) throws URISyntaxException, ExecutionException,
     InterruptedException {
final String URL = "https://jsonplaceholder.typicode.com/users/1";
    
HttpRequest request = HttpRequest.newBuilder(new URI(URL)).GET().timeout(Duration.of(10, ChronoUnit.SECONDS)).build();
    
CompletableFuture<Void> response = HttpClient.newHttpClient()
                    .sendAsync(request, HttpResponse.BodyHandlers.ofString())
                    .thenAcceptAsync(r -> {
                System.out.println(r.statusCode());
                System.out.println(Thread.currentThread().getName());
}, Executors.newFixedThreadPool(10));
    
 response.get();//wait for API response
 System.out.println("END OF PROGRAM");
}

Output：

200
pool-1-thread-1
END OF PROGRAM