当代码头<%@报这个“The superclass “javax.servlet.http.HttpServlet” was not
found on the Java Build Path”错误时，可能是项目没有添加tomcat库导致的，解决办法如下:
- 找到报错的项目，右击选择Build Path >> Configure Build Path…
The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path错误解决办法 - 依次选择Java Build Path >> Libraries >> Add Library
The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path错误解决办法 - 选择Server Runtime,然后Next
The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path错误解决办法 - 选择你创建该项目时所使用的tomcat版本，这里我是7.0，所以选第一个，然后Finish
The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path错误解决办法 - 应用更改与关闭即可
The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path错误解决办法
做完以上步骤后，错误就消失了，项目就能正常运行了