[sts4] spring 에러 - The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path / javax.servlet.ServletException cannot be resolved to a type

workspace 파일을 옮겼더니 에러 발생. 에러는 다음과 같다.

The superclass "javax.servlet.http.HttpServlet" was not found on the Java Build Path Multiple annotations found at this line: - javax.servlet.ServletException cannot be resolved to a type - javax.servlet.jsp.PageContext cannot be resolved to a type - javax.servlet.jsp.JspException cannot be resolved to a type 환경이 바뀌어서 제대로 서버환경을 안 잡아줘서 생기는 오류였다. 해결 방법 1.

오류가.....