如何为Spark Java应用程序获取自动定义的端口？

在Java Spark（不是Apache Spark）的API文档中，可以指定端口0，使其自动选择端口。太好了

但是，我不知道在服务器启动后如何获取该端口。我可以在日志中看到：

15:41:12.459 [Thread-2] INFO  spark.webserver.JettySparkServer - >> Listening on 0.0.0.0:63134

但是我需要能够以编程的方式进行测试，这样我的集成测试每次都能够可靠地运行

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那么如何获得该端口呢？

我无法在API中获得该信息，因此我提交了一份申请

我能通过一堆丑陋的倒影找到它：

/**
 * Meant to be called from a different thread, once the spark app is running
 * This is probably only going to be used during the integration testing process, not ever in prod!
 *
 * @return the port it's running on
 */
public static int awaitRunningPort() throws Exception {
    awaitInitialization();
    //I have to get the port via reflection, which is fugly, but the API doesn't exist :(
    //Since we'll only use this in testing, it's not going to kill us
    Object instance = getInstance();
    Class theClass = instance.getClass();
    Field serverField = theClass.getDeclaredField("server");
    serverField.setAccessible(true);
    Object oneLevelDeepServer = serverField.get(instance);

    Class jettyServerClass = oneLevelDeepServer.getClass();
    Field jettyServerField = jettyServerClass.getDeclaredField("server");
    jettyServerField.setAccessible(true);
    //Have to pull in the jetty server stuff to do this mess
    Server jettyServer = (Server)jettyServerField.get(oneLevelDeepServer);

    int acquiredPort = ((ServerConnector)jettyServer.getConnectors()[0]).getLocalPort();

    log.debug("Acquired port: {}", acquiredPort);
    return acquiredPort;
}

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在我们的集成测试中，这对我来说很好，但我不使用https，而且它通过获取反射保护字段深入API大约两个层次。我找不到其他方法来做这件事。很高兴被证明是错误的。

这将在Spark 2.6.0上起作用：

public static int start (String keystoreFile, String keystorePw)
{
    secure(keystoreFile, keystorePw, null, null);
    port(0);

    staticFiles.location("/public");

    get(Path.CLOCK, ClockController.time);
    get(Path.CALENDAR, CalendarController.date);

    // This is the important line. It must be *after* creating the routes and *before* the call to port()
    awaitInitialization();

    return port();
}

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如果不调用waitingInitialization（），port（）将返回0。

Sparks自己的测试中有什么内容吗？他们在测试中使用硬编码端口，而不是随机端口：(