我们如何将 play.libs.concurrent.HttpExecutionContext

Question

在一个播放框架项目控制器中，我正在使用 forEach() 处理一个对象列表，它工作正常。List<Post> posts = repository.getPosts();posts.forEach(post -> {    //...some processing    anyFunc(); //<-- internally uses HttpExecutionContext    //...further processing});但是当我尝试使用 parallelStream() 并行处理这些对象列表以提高性能时，我在并行流中丢失了 HttpExecutionContext 实例。List<Post> posts = repository.getPosts();posts.parallelStream().forEach(post -> {    //...some processing    anyFunc(); //<-- not able to use HttpExecutionContext now    //...further processing});我无法将 HttpExecutionContext 作为参数传递给anyFunc. 有什么方法可以在 parallelStream() 中传递/设置 HttpExecutionContext 吗？

Answer 1

使用HttpExecutionContext.execute

public class HomeController extends Controller {

    @Inject HttpExecutionContext ec;

    public Result index() {

        // The data to parallel processing

        List<String> list = List.of("Item 1", "Item 2", "Item 3","Item 4", "Item 5", "Item 6", "Item 7", "Item 8");

        // Make a Stream. The `parallelStream` is not used because 

        // `current.execute` will make it run in parallel.

        Stream<String> listInParralel = list.stream(); 

        // The current executor with the HTTP context. 

        Executor current = ec.current();

        System.out.println("START");

        listInParralel.forEach(item -> {

          current.execute(()-> {

            // request().uri() internally uses HttpExecutionContext

            System.out.println("item: " + item + " in "  +  request().uri()  + "(" + Thread.currentThread().getName() + ")");

          });

        });

        // Results

        /*

        START

        item: Item 7 in /(application-akka.actor.default-dispatcher-9)

        item: Item 5 in /(application-akka.actor.default-dispatcher-7)

        item: Item 3 in /(application-akka.actor.default-dispatcher-5)

        item: Item 1 in /(application-akka.actor.default-dispatcher-6)

        item: Item 6 in /(application-akka.actor.default-dispatcher-8)

        item: Item 4 in /(application-akka.actor.default-dispatcher-2)

        item: Item 2 in /(application-akka.actor.default-dispatcher-4)

        item: Item 8 in /(application-akka.actor.default-dispatcher-9)

        */

        return ok("Done");

    }

}

不过，我更喜欢缓存 HTTP 数据，然后在并行处理中使用它们。不喜欢打扰HttpExecutionContext：

public class HomeController extends Controller {

    @Inject HttpExecutionContext ec;

    public Result index() {

        // The data to parallel processing

        List<String> list = List.of("Item 1", "Item 2", "Item 3","Item 4", "Item 5", "Item 6", "Item 7", "Item 8");

        Stream<String> listInParralel = list.parallelStream(); 

        // Take all that you need from the HttpExecutionContext.  

        String uri = request().uri();

        System.out.println("START");

        listInParralel.forEach(item -> {

            // use pre cached HTTP context data, liek `uri`

            System.out.println("item: " + item + " in "  +  uri  + "(" + Thread.currentThread().getName() + ")");

        });

        // Results

        /*

        START

        item: Item 1 in /(ForkJoinPool.commonPool-worker-7)

        item: Item 8 in /(ForkJoinPool.commonPool-worker-3)

        item: Item 7 in /(ForkJoinPool.commonPool-worker-15)

        item: Item 4 in /(ForkJoinPool.commonPool-worker-9)

        item: Item 3 in /(ForkJoinPool.commonPool-worker-13)

        item: Item 2 in /(ForkJoinPool.commonPool-worker-5)

        item: Item 5 in /(ForkJoinPool.commonPool-worker-11)

        item: Item 6 in /(application-akka.actor.default-dispatcher-4)

        */

        return ok("Done");

    }

}