java – Play 2.5升级错误：CompletionException – 此处没有可用的HTTP上下文

参见英文答案 > Play Framework 2.5 JavaAsync throwing CompletionException                                    2个
在示例应用程序上从Play 2.4升级到Play 2.5后,当我运行./activator clean dist时,我没有遇到任何错误,但是在转到特定端点http：// localhost：9000 / java / proxy后,我收到了以下错误：

[error] application - 

! @72keog237 - Internal server error, for (GET) [/java/proxy] ->

play.api.http.HttpErrorHandlerExceptions$$anon$1: Execution exception[[CompletionException: java.lang.RuntimeException: There is no HTTP Context available from here.]]
    at play.api.http.HttpErrorHandlerExceptions$.throwabletoUsefulException(HttpErrorHandler.scala:293)
    at play.api.http.DefaultHttpErrorHandler.onServerError(HttpErrorHandler.scala:220)
    at play.api.GlobalSettings$class.onError(GlobalSettings.scala:160)
    at play.api.DefaultGlobal$.onError(GlobalSettings.scala:188)
    at play.api.http.GlobalSettingsHttpErrorHandler.onServerError(HttpErrorHandler.scala:100)
    at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:100)
    at play.core.server.netty.PlayRequestHandler$$anonfun$2$$anonfun$apply$1.applyOrElse(PlayRequestHandler.scala:99)
    at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:344)
    at scala.concurrent.Future$$anonfun$recoverWith$1.apply(Future.scala:343)
    at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
Caused by: java.util.concurrent.CompletionException: java.lang.RuntimeException: There is no HTTP Context available from here.
    at java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:273)
    at java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:280)
    at java.util.concurrent.CompletableFuture.uniapply(CompletableFuture.java:604)
    at java.util.concurrent.CompletableFuture$uniapply.tryFire(CompletableFuture.java:577)
    ... 5 common frames omitted
Caused by: java.lang.RuntimeException: There is no HTTP Context available from here.
    at play.mvc.Http$Context.current(Http.java:62)
    at play.mvc.Controller.response(Controller.java:81)
    at controllers.JavaController$4.apply(JavaController.java:107)
    at controllers.JavaController$4.apply(JavaController.java:103)
    at java.util.concurrent.CompletableFuture.uniapply(CompletableFuture.java:602)
    at java.util.concurrent.CompletableFuture$uniapply.tryFire(CompletableFuture.java:577)
    at java.util.concurrent.CompletableFuture$Completion.exec(CompletableFuture.java:443)
    at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
    at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
    at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)

我一直在使用Replaced F.Promise with Java 8’s CompletionStage中的指南替换F.Promise,map和flatMap以及上一个链接的建议替换(下面反映的更改片段).

  public CompletionStage<Result> proxy() {
    final  CompletionStage<WSResponse> responsePromise = WS.url("http://example.com").get();

    Logger.info("Before map");
    final CompletionStage<Result> resultPromise = responsePromise.thenApplyAsync(
        new Function<WSResponse, Result>() {
          @Override
          public Result apply(WSResponse wsResponse) {
            Logger.info("Within map");
            response().setContentType(wsResponse.getHeader("Content-Type"));
            return ok(wsResponse.getBody());
          }
        }
    );

回到2.4时,我没有收到此错误,http：// localhost：9000 / java / proxy端点成功运行.

在使用此public sample app on github替换代理方法中的相应替换调用之后,我不断获得上面的无HTTP上下文可用错误.我也在Java8Controller class中使用http：// localhost：9000 / java8 / proxy端点获得了相同的结果.

我发现其他人遇到过这个问题,到目前为止我已经能够猜测我需要拨打HttpExecutionContext和/或使用supplyAsync,尽管我在将这些知识转移到这个例子时遇到了麻烦.也许有人可以举一两个(或三个)关于我如何解决这个错误的例子？欢迎任何建议,并提前感谢您.

解决方法:

根据Play Documentation,在Action中使用Java CompletionStage时,必须显式提供HTTP执行上下文作为执行程序.
 因此,您可以在Action中注入HTTP Context.

public class Application extends Controller {
@Inject HttpExecutionContext ec;

public CompletionStage<Result> index() {
    someCompletableFuture.supplyAsync(() -> { 
      // do something with request()
    }, ec.current());
  }
}

希望有所帮助.