An unknown server-side error occurred while processing the command

Hi All,
An Error occurred when I want to start an app.Please help me ,thank you!
Code:
@BeforeClass(alwaysRun = true)
public void setUp() throws Exception {
// set up appium

    DesiredCapabilities capabilities = new DesiredCapabilities();
    capabilities.setCapability(CapabilityType.BROWSER_NAME, "iOS");
    capabilities.setCapability("platformName", "Mac");
    capabilities.setCapability("deviceName", "iPhone 6s Plus");
    capabilities.setCapability("platformVersion", "9.3");
    // if no need install don't add this
    if (isInstall) {
        File classpathRoot = new File(System.getProperty("user.dir"));
        File appDir = new File(classpathRoot, "apps");
        File app = new File(appDir, "TestApp.app");
        System.out.println("---->"+app.getAbsolutePath());
        capabilities.setCapability("app", app.getAbsolutePath());
    }
 // support Chinese
    capabilities.setCapability("unicodeKeyboard", "True");
    capabilities.setCapability("resetKeyboard", "True");

    driver = new IOSDriver (new URL("http://127.0.0.1:4723/wd/hub"),
            capabilities);
}

Error:
FAILED CONFIGURATION: @BeforeClass setUp
org.openqa.selenium.WebDriverException: An unknown server-side error occurred while processing the command. Original error: Could not get Xcode version. /Library/Developer/Info.plist does not exist on disk. (WARNING: The server did not provide any stacktrace information)
Command duration or timeout: 757 milliseconds
Build info: version: ‘2.53.0’, revision: ‘35ae25b’, time: ‘2016-03-15 16:57:40’
System info: host: ‘IBMUSER-no-MacBook-Air.local’, ip: ‘9.112.93.75’, os.name: ‘Mac OS X’, os.arch: ‘x86_64’, os.version: ‘10.11.5’, java.version: ‘1.8.0_111’
Driver info: io.appium.java_client.ios.IOSDriver
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:206)
at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:158)
at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:678)
at io.appium.java_client.DefaultGenericMobileDriver.execute(DefaultGenericMobileDriver.java:40)
at io.appium.java_client.AppiumDriver.execute(AppiumDriver.java:1)
at io.appium.java_client.ios.IOSDriver.execute(IOSDriver.java:1)
at org.openqa.selenium.remote.RemoteWebDriver.startSession(RemoteWebDriver.java:249)
at org.openqa.selenium.remote.RemoteWebDriver.(RemoteWebDriver.java:131)
at org.openqa.selenium.remote.RemoteWebDriver.(RemoteWebDriver.java:144)
at io.appium.java_client.DefaultGenericMobileDriver.(DefaultGenericMobileDriver.java:36)
at io.appium.java_client.AppiumDriver.(AppiumDriver.java:114)
at io.appium.java_client.AppiumDriver.(AppiumDriver.java:132)
at io.appium.java_client.ios.IOSDriver.(IOSDriver.java:82)
at TestNG.Test_1.setUp(Test_1.java:43)
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:498)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:85)
at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:510)
at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:211)
at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:138)
at org.testng.internal.TestMethodWorker.invokeBeforeClassMethods(TestMethodWorker.java:170)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:104)
at org.testng.TestRunner.privateRun(TestRunner.java:774)
at org.testng.TestRunner.run(TestRunner.java:624)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:359)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:354)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:312)
at org.testng.SuiteRunner.run(SuiteRunner.java:261)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1215)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1140)
at org.testng.TestNG.run(TestNG.java:1048)
at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:132)
at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:236)
at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:81)

===============================================
Default test

Do you have XCode and XCode Command Line Tools installed in your machine?

Yes,I have Xcode in my manchine.My Xcode version is 7.1

Can you navigate to the path /Library/Developer/Info.plist and check if this file exists. Navigate to the specified path using terminal .

Have you started Xcode at least once?

There is no Info.plist in /Library/Developer.What should I do?

Yes,I have Started Xcode at least once.

When your app was built in Xcode was it set to “Development Target”?