Javaweb error: The superclass“javax.servlet.http.HttpServlet” was not found on the Java Build Path

Error: The superclass “javax.servlet.http.HttpServlet” was not found on the Java Build Path

原因： 这是因为在Java build path 没有添加tomcat 运行时

解决方法：

右击web工程–》属性或Build Path-》Java Build Path->Libraries-> Add Libray…->Server Runtime –》Tomcat Server