HTTP Status 500 에러

다음과 같은 오류가 왜 발생하는지 알 수 있을까요

HTTP Status 500 - An exception occurred processing JSP page /mypage/cartDelete.jsp at line 9

type Exception report

message An exception occurred processing JSP page /mypage/cartDelete.jsp at line 9

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: An exception occurred processing JSP page /mypage/cartDelete.jsp at line 9

6: String url = "cartList.jsp";
7:
8: String[] cseqArr = request.getParameterValues("cesq");
9: System.out.println(cseqArr.length);
10:
11: for (String cseq:cseqArr) {
12: System.out.println(cseq);

Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:574)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.NullPointerException
org.apache.jsp.mypage.cartDelete_jsp._jspService(cartDelete_jsp.java:118)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.0.33 logs.