JUnit test rule to take screenshot using Selenium Web Driver when test failed

TakeScreenshotOnFailRule.java

public class TakeScreenshotOnFailRule extends TestWatcher {
  	protected String _folder;
	protected WebDriver _driver;
	public TestRule(WebDriver driver, String folder) {
		_folder = folder;
		_driver = driver;
	}

	@Override
	protected void failed(Throwable e, Description description) {
		super.failed(e, description);
		String name = description.getDisplayName();
		name = _folder + "\\" + name + ".png";
		
		File screenshot = ((TakesScreenshot)_driver).getScreenshotAs(OutputType.FILE);
		try {
			FileUtils.copyFile(screenshot, new File(name));
		} catch (Exception ex) {
			throw new RuntimeException(ex);
		}
	}
}