Listener Code

package Tests;
import java.lang.reflect.Field;
import org.testng.ITestContext;
import org.testng.ITestListener;
import org.testng.ITestResult;
import framework.LogWriter;
import framework.ScreenshotWriter;
import org.openqa.selenium.OutputType;
import org.openqa.selenium.TakesScreenshot;
import org.openqa.selenium.WebDriver;
public class Listener implements ITestListener {
 
  private LogWriter traceWriter;
  private LogWriter exceptionsWriter;
	
  public Listener()
  {
     this.exceptionsWriter = new LogWriter("./target/logs", "exceptions.log");
     this.traceWriter      = new LogWriter("./target/logs", "trace.log");
  }
  @Override
  public void onTestStart(ITestResult testResult) 
  {  	  
     this.traceWriter.writeToLog("\n Test Name: " + testResult.getName());
  }
 
  	
  @Override
  public void onTestSuccess(ITestResult testResult) 
  {
      byte[] screenshotInfo = getScreenshot(testResult);
	  
      saveScreenshot(screenshotInfo, "passed_" + testResult.getName());   
  }
 
  	    
  @Override
  public void onTestFailure(ITestResult testResult) 
  { 
      byte[] screenshotInfo = getScreenshot(testResult);
      saveScreenshot(screenshotInfo, "failed_" + testResult.getName());
    	
      saveExceptionInfo(testResult);
  }	
  	  
  private byte[] getScreenshot(ITestResult testResult)
  {
       TakesScreenshot driver = (TakesScreenshot)driver(testResult);    	
  
       byte[] screenshotInfo = driver.getScreenshotAs(OutputType.BYTES);
       return screenshotInfo;
  }
  	  
  private void saveScreenshot(byte[] screenshotInfo, 
                                String testName)
  {
       ScreenshotWriter writer = new ScreenshotWriter();  
  	
       writer.writeToFile(screenshotInfo, testName);
  }
  	  
  private void saveExceptionInfo(ITestResult testResult)
  {
      String testName = testResult.getName();
      String exceptionName = testResult.getThrowable().getMessage();
      
      String stackTrace = "";     
      StackTraceElement[] stackElements = 
           testResult.getThrowable().getStackTrace();
      
      for (int i = 0; i < stackElements.length - 1; i++)
         stackTrace = stackTrace + stackElements[i].toString() + "\n";        	
      
      this.exceptionsWriter.writeToLog(
         String.format(
          "test = %s\n exception = %s\n stack trace = %s\n",
      	  testName,
      	  exceptionName,
      	  stackTrace));
  }
  
  
  @SuppressWarnings("unchecked")
  private WebDriver driver(ITestResult result)      
  {
  
       try {
     	  Class<?extends ITestResult> testClass = 
             (Class<? extends ITestResult>)result.getInstance().getClass();      
      
    	  Class<?extends ITestResult> baseClass = 
             (Class<? extends ITestResult>)testClass.getSuperclass();
      
    	  Field field = baseClass.getDeclaredField("driver");      
    	
          WebDriver driver = (WebDriver)field.get(result.getInstance());
      
          return driver;
      }  
      catch (
        SecurityException | NoSuchFieldException | IllegalAccessException | IllegalArgumentException e) 
      {
    	throw new IllegalStateException(
           "could not get the driver!", e);
      }
 
    }
  
    @Override
    public void onTestSkipped(ITestResult result) 
    {
    }
  
    @Override
    public void onTestFailedButWithinSuccessPercentage(ITestResult r) 
    {
    }
  
    @Override
    public void onStart(ITestContext context) 
    {
    }
  
    @Override
    public void onFinish(ITestContext c) 
    {
    }
  
}