以下问题在采访中问。让不同的服务相互调用,有一个服务A,它调用服务B需要20秒。 Service A也在调用Service C和Service D,它们分别花费25秒和20秒。当服务A从B,C,D获得响应时,它必须返回到前端响应。您将如何实现这一目标。
我认为Interviewer的意思是从并发请求多线程或ExecutorService。因此,我告诉我们可以从Callable接口使用FutureObect Return。为此,我编写了以下代码:以下代码正在工作并返回结果:45,这是正确的。
当一个应用程序依赖于另一个应用程序结果时,我的方法是正确的吗?在实际应用中,我们是否采用以下方法?请让我知道代码中是否有任何更正?
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;
class Result{
String applicationName;
int result;
public Result(String applicationName, int result){
this.applicationName = applicationName;
this.result = result;
}
public void add(int value){
this.result += value;
}
public int getResult() {
return result;
}
}
class ApplicationA implements Callable<Result>{
@Override
public Result call() throws Exception {
ExecutorService executorService = Executors.newFixedThreadPool(10);
List<Future<Result>> list = new ArrayList<Future<Result>>();
Future<Result> futureB = executorService.submit(new ApplicationB());
list.add(futureB);
Future<Result> futureC = executorService.submit(new ApplicationC());
list.add(futureC);
Future<Result> futureD = executorService.submit(new ApplicationD());
list.add(futureD);
Result result = new Result("ApplicationA", 12);
for(Future<Result> future: list){
try {
Result result1 = future.get();
result.add(result1.getResult());
}catch (InterruptedException | ExecutionException e){
e.printStackTrace();
}
}
executorService.shutdown();
return result;
}
}
class ApplicationB implements Callable<Result>{
@Override
public Result call() throws Exception {
Thread.sleep(20000);
return new Result("ApplicationB",10);
}
}
class ApplicationC implements Callable<Result>{
@Override
public Result call() throws Exception {
Thread.sleep(25000);
return new Result("ApplicationC",11);
}
}
class ApplicationD implements Callable<Result>{
@Override
public Result call() throws Exception {
Thread.sleep(20000);
return new Result("ApplicationD",12);
}
}
public class MultiApplicationDemo {
public static void main(String[] args) throws ExecutionException, InterruptedException {
ExecutorService executorService = Executors.newSingleThreadExecutor();
Future<Result> futureA = executorService.submit(new ApplicationA());
System.out.println(futureA.get().getResult());
executorService.shutdown();
}
}
Future
的使用是阻止操作。另一方面,CompletableFuture将为您提供非阻塞机制。除Future
接口外,它还具有CompletionStage
接口,可用于通过管道传递多个操作。
CompletableFuture<String> completableFuture
= CompletableFuture.supplyAsync(() -> "Hello")
.thenCompose(s -> CompletableFuture.supplyAsync(() -> s + " World"));
如果有任何请求的服务抛出异常,它还会使您优雅地失败。