public static WebDriver getDriver(){
			WebDriver driver= DriverManager.ThreadDriver.get();
			if (driver==null){
				if (browserType.equals("firefox")){
					 driver = new EventFiringWebDriver(new FirefoxDriver()).register(new LogEventListener());
					 ThreadDriver.set(driver);
					//找东西前等三秒wait 3 second for every find by
				    DriverManager.getDriver().manage().timeouts().implicitlyWait(3, TimeUnit.SECONDS);
				}
				//有需求的同学自己在这里添加IE等浏览器的支持
				//you can add ie/chrome or other driver here
				}
			return driver;
		}