selenium java.lang.IllegalStateException: must be set by the webdriver.gecko.driver

 java.lang.IllegalStateException: The path to the driver executable must be set by the webdriver.gecko.driver system property; for more information, seehttps://github.com/mozilla/geckodriver. 

selenium 打开firefox时报错

原因是使用了最新的selenium webdriver版本Selenium 3.x，此版本不支持直接启动firefox，必须要先设置SystemProperty 

下载最新版本的geckoDriver 

https://github.com/mozilla/geckodriver/releases

如果github官网不能访问，请参考http://blog.csdn.net/fabbychips/article/details/53488802

Check if Firefox is 32-bit or 64-bit

There are two versions of GeckoDriver for Windows: 32-bit and 64-bit. Based on whether your Firefox is 32-bit or 64-bit, you need to download the corresponding GeckoDriver exe. In this section, you will first check whether your Firefox is 32-bit or 64-bit