에러 : The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path

JSP 파일 제일 첫번째 라인에 뜨는 에러

The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path

해결법

프로젝트 우클릭 -> Build Path -> Configure Build Path...-> Libraries 탭 -> add library -> server runtime -> was 선택