解决办法：安装 Eclipse Java EE Developer Tools 和 Eclipse Java Web Developer Tools
Help -> Install New Software
Work with下拉框中选择：Oxygen - http://download.eclipse.org/releases/oxygen
注：oxygen是eclipse版本号
展开 Web, XML, Java EE and OSGI Enterprise Development 选项，选择 Eclipse Java EE Developer Tools 和 Eclipse Java Web Developer Tools 安装