Javaweb: Error message the superclass "Javax.servlet.http.HttpServlet" is not found on the Java build Path

Javaweb: Error message the superclass "Javax.servlet.http.HttpServlet" is not found on the Java build Path
For a long time, I did not write JSP, and today I built a Javaweb project and configured the Web container tomcat in Eclipse. Originally happy to create a new JSP page, add a simple Java class. However, the top of the JSP page appears with a "Red" error message: The superclass "Javax.servlet.http.HttpServlet" is not found on the Java build Path. The original Javaweb engineering class was not added to the Tomcat runtime related class cause. The following are the specific solutions: 1, right-click Web Engineering-Properties or build path-, Java build path->libraries-> Add libray...->server Runtime-"Tomcat" Server 2, switch to Orader and Export in the Java Build path interface, select Tomcat.
Note: When you do this, if you open the server runtime after a blank, you need to set the Apache server. Set the method to: Window->preferences->server->runtime environment-> Add--> Select Apache version after dot next, Then fill in your Apache Server Software installation (after decompression) address.