我正在尝试在eclipse/maven项目上使用selenium网格在多个设备上执行appium脚本。
参考以下教程：https://www.youtube.com/watch?v=xsvjc_1zhqm&list=pluedilio4thhz9tkkg3uluypfxe4soufy&index=2
但是，当我作为“testng”测试运行时，会出现以下错误：

org.openqa.selenium.WebDriverException: Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:17:03'
System info: host: 'DESKTOP-E205GQ8', ip: '192.168.0.105', os.name: 'Windows 10', os.arch: 'amd64', os.version: '10.0', java.version: '1.8.0_261'
Driver info: driver.version: RemoteWebDriver
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:214)
    at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:166)
    at org.openqa.selenium.remote.JsonWireProtocolResponse.lambda$errorHandler$0(JsonWireProtocolResponse.java:54)
    at org.openqa.selenium.remote.HandshakeResponse.lambda$getResponseFunction$0(HandshakeResponse.java:30)
    at org.openqa.selenium.remote.ProtocolHandshake.lambda$createSession$0(ProtocolHandshake.java:126)
    at java.util.stream.ReferencePipeline$3$1.accept(Unknown Source)
    at java.util.Spliterators$ArraySpliterator.tryAdvance(Unknown Source)
    at java.util.stream.ReferencePipeline.forEachWithCancel(Unknown Source)
    at java.util.stream.AbstractPipeline.copyIntoWithCancel(Unknown Source)
    at java.util.stream.AbstractPipeline.copyInto(Unknown Source)
    at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
    at java.util.stream.FindOps$FindOp.evaluateSequential(Unknown Source)
    at java.util.stream.AbstractPipeline.evaluate(Unknown Source)
    at java.util.stream.ReferencePipeline.findFirst(Unknown Source)
    at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:128)
    at org.openqa.selenium.remote.ProtocolHandshake.createSession(ProtocolHandshake.java:74)
    at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:136)
    at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:552)
    at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:213)
    at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:131)
    at org.openqa.selenium.remote.RemoteWebDriver.<init>(RemoteWebDriver.java:144)
    at com.testautomation.grid.AppiumSeGridDemo.test1(AppiumSeGridDemo.java:23)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:124)
    at org.testng.internal.Invoker.invokeMethod(Invoker.java:583)
    at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:719)
    at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:989)
    at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:125)
    at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:109)
    at org.testng.TestRunner.privateRun(TestRunner.java:648)
    at org.testng.TestRunner.run(TestRunner.java:505)
    at org.testng.SuiteRunner.runTest(SuiteRunner.java:455)
    at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:450)
    at org.testng.SuiteRunner.privateRun(SuiteRunner.java:415)
    at org.testng.SuiteRunner.run(SuiteRunner.java:364)
    at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
    at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:84)
    at org.testng.TestNG.runSuitesSequentially(TestNG.java:1208)
    at org.testng.TestNG.runSuitesLocally(TestNG.java:1137)
    at org.testng.TestNG.runSuites(TestNG.java:1049)
    at org.testng.TestNG.run(TestNG.java:1017)
    at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:115)
    at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:251)
    at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:77)
Caused by: java.lang.NullPointerException
    at java.util.HashMap.putMapEntries(Unknown Source)
    at java.util.HashMap.putAll(Unknown Source)
    at org.openqa.selenium.remote.DesiredCapabilities.<init>(DesiredCapabilities.java:55)
    at org.openqa.grid.web.servlet.handler.RequestHandler.process(RequestHandler.java:104)
    at org.openqa.grid.web.servlet.DriverServlet.process(DriverServlet.java:83)
    at org.openqa.grid.web.servlet.DriverServlet.doPost(DriverServlet.java:67)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
    at org.seleniumhq.jetty9.servlet.ServletHolder.handle(ServletHolder.java:841)
    at org.seleniumhq.jetty9.servlet.ServletHandler.doHandle(ServletHandler.java:543)
    at org.seleniumhq.jetty9.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:188)
    at org.seleniumhq.jetty9.server.session.SessionHandler.doHandle(SessionHandler.java:1584)
    at org.seleniumhq.jetty9.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:188)
    at org.seleniumhq.jetty9.server.handler.ContextHandler.doHandle(ContextHandler.java:1228)
    at org.seleniumhq.jetty9.server.handler.ScopedHandler.nextScope(ScopedHandler.java:168)
    at org.seleniumhq.jetty9.servlet.ServletHandler.doScope(ServletHandler.java:481)
    at org.seleniumhq.jetty9.server.session.SessionHandler.doScope(SessionHandler.java:1553)
    at org.seleniumhq.jetty9.server.handler.ScopedHandler.nextScope(ScopedHandler.java:166)
    at org.seleniumhq.jetty9.server.handler.ContextHandler.doScope(ContextHandler.java:1130)
    at org.seleniumhq.jetty9.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
    at org.seleniumhq.jetty9.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
    at org.seleniumhq.jetty9.server.Server.handle(Server.java:564)
    at org.seleniumhq.jetty9.server.HttpChannel.handle(HttpChannel.java:320)
    at org.seleniumhq.jetty9.server.HttpConnection.onFillable(HttpConnection.java:251)
    at org.seleniumhq.jetty9.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:279)
    at org.seleniumhq.jetty9.io.FillInterest.fillable(FillInterest.java:112)
    at org.seleniumhq.jetty9.io.ChannelEndPoint$2.run(ChannelEndPoint.java:124)
    at org.seleniumhq.jetty9.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:672)
    at org.seleniumhq.jetty9.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:590)
    at java.lang.Thread.run(Unknown Source)

appium java类如下所示：

package com.testautomation.grid;

import java.net.URL;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.remote.DesiredCapabilities;
import org.openqa.selenium.remote.RemoteWebDriver;
import org.testng.annotations.Test;

public class AppiumSeGridDemo {
    @Test
    public void test1() {
        try {
            System.out.println("Test1 Exceution Started");
            DesiredCapabilities caps = new DesiredCapabilities();
            caps.setCapability("udid", "ZH33L2Z6KL");
            caps.setCapability("deviceName", "ZH33L2Z6KL");
            caps.setCapability("platformName", "Android");          
            caps.setCapability("automationName", "UiAutomator2");           
            caps.setCapability("appPackage", "com.google.android.calculator");
            caps.setCapability("appActivity", "com.android.calculator2.Calculator");            
            caps.setCapability("systemPort", "8201");
            WebDriver driver = new RemoteWebDriver(new URL("http://192.168.0.105:4444/wd/hub"), caps);          
            Thread.sleep(5000);
            driver.quit();
            System.out.println("Test1 Exceution Ended");
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}

pom.xml如下：

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.grid.demo</groupId>
  <artifactId>AppiumGridDemo</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <name>AppiumGridDemo</name>
  <description>AppiumGridDemo</description>
  <dependencies>
    <dependency>
            <groupId>org.seleniumhq.selenium</groupId>
            <artifactId>selenium-server</artifactId>
            <version>3.141.59</version>
    </dependency>
    <dependency>
            <groupId>org.testng</groupId>
            <artifactId>testng</artifactId>
            <version>6.14.3</version>
            <scope>test</scope>
    </dependency>
    <dependency>
            <groupId>io.appium</groupId>
            <artifactId>java-client</artifactId>
            <version>7.3.0</version>
    </dependency>
  </dependencies>
</project>

selenium独立服务器使用以下命令调用：

java -jar selenium-server-standalone-3.141.59.jar -role hub

将创建一个json文件（nodeconfig\u device1.json）来运行节点

{
  "capabilities": [
    {
      "browserName": "Android",
      "version": "6.0",
      "maxInstances": 1,      
      "deviceName": "ZH33L2Z6KL",
      "platformName": "ANDROID",
      "automationName":"UiAutomator2",
      "systemPort":"8201"
    }
  ],
  "configuration": {
    "cleanUpCycle": 2000,
    "timeout": 30000,
    "proxy": "org.openqa.grid.selenium.proxy.DefaultRemoteProxy",    
    "maxSession": 1,        
    "register": true,
    "registerCycle": 5000,
    "hubPort": 4444,
    "hubHost": "192.168.0.105",
    "hubProtocol":"http"
  }
}

使用以下命令执行json文件：

appium --port 6001 --nodeconfig nodeconfig_device1.json

节点正在集线器中正确注册。但是当testng测试运行时，计算器应用程序并没有启动。
问题
少了什么？为什么testng测试会崩溃？
有任何安装问题吗？
是否存在任何配置问题？
为什么不创建remotewebdriver？
请提供这个问题的解决方案