[Eclipse]错误:The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path

Eclipse错误
导入已有的Dynamic Web app工程时jsp页面代码出现错误提示：
The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path
解决：Build Path > Configure Build Path > libraries > Add Libraried > Server Runtime > tomcat; Order and Export > 选中 Apache tomcat