title: Appium error when trying to build the AppiumServiceBuilder
body: <p>I am building the service correctly from what I have been reading. What is the cause of the following error and how can I fix it? I have the Selenium Standalone Server with the Java client for Appium. </p>
  
  <p>My code:</p>
  
  <pre><code>AppiumServiceBuilder appiumService = new AppiumServiceBuilder()
                  .usingDriverExecutable(new File("/Applications/Appium.app/Contents/Resources/node/bin/node"))
                  .withAppiumJS(new File("/Applications/Appium.app/Contents/Resources/node_modules/appium/bin/appium.js"));
      appiumService.usingPort(4723);
  
      appiumService.build();
  </code></pre>
  
  <p>Error stack Trace:</p>
  
  <pre><code>java.lang.NoClassDefFoundError: org/apache/commons/validator/routines/InetAddressValidator
      at io.appium.java_client.service.local.AppiumServiceBuilder.createArgs(AppiumServiceBuilder.java:230)
      at org.openqa.selenium.remote.service.DriverService$Builder.build(DriverService.java:299)
      at com.wolff.utils.Driver.startAppium(Driver.java:53)
      at com.wolff.utils.Driver.setUp(Driver.java:29)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:497)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
      at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
      at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.junit.runners.Suite.runChild(Suite.java:128)
      at org.junit.runners.Suite.runChild(Suite.java:27)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
  Caused by: java.lang.ClassNotFoundException: org.apache.commons.validator.routines.InetAddressValidator
      at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
      at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
      at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
      ... 28 more
  
  java.lang.NullPointerException
      at com.wolff.utils.Driver.tearDown(Driver.java:44)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:497)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
      at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
      at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
      at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:33)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.junit.runners.Suite.runChild(Suite.java:128)
      at org.junit.runners.Suite.runChild(Suite.java:27)
      at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
      at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
      at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
      at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
      at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
      at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
      at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
      at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
      at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
  </code></pre>