org.apache.catalina.core.ApplicationDispatcher invoke 초보 개발자 도와주세요

Question

의류 쇼핑몰 홈페이지 구현 MVC 형태로 연습 해보고 있는데 1. com.controller.main/MainServlet.java에서 ctrl + F11하면 list가 잘 나옵니다 2. WebContect/main.jsp에서 ctrl + F11하면 Webcontent/goods/goodsList.jsp를 거쳐서 View하려는건데이런 오류가 뜹니다;;오후 org.apache.catalina.core.ApplicationDispatcher invoke 심각: 서블릿 [jsp]을(를) 위한 Servlet.service() 호출이 예외를 발생시켰습니다. java.lang.NullPointerException at org.apache.jsp.goods.goodsList_jsp._jspService(goodsList_jsp.java:139) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:713) at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:583) at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:519) at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:865) at org.apache.jsp.main_jsp._jspService(main_jsp.java:137) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:615) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1626) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source) 8월 27, 2021 10:26:23 오후 org.apache.catalina.core.StandardWrapperValve invoke 심각: 경로 [/프로젝트 이름]의 컨텍스트 내의 서블릿 [jsp]을(를) 위한 Servlet.service() 호출이, 근본 원인(root cause)과 함께, 예외 [org.apache.jasper.JasperException: java.lang.NullPointerException]을(를) 발생시켰습니다. java.lang.NullPointerException at org.apache.jsp.goods.goodsList_jsp._jspService(goodsList_jsp.java:139) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:713) at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:583) at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:519) at org.apache.jasper.runtime.JspRuntimeLibrary.include(JspRuntimeLibrary.java:865) at org.apache.jsp.main_jsp._jspService(main_jsp.java:137) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:71) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:476) at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:386) at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:330) at javax.servlet.http.HttpServlet.service(HttpServlet.java:733) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:543) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:615) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:818) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1626) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source) 서블릿 코드는 이거고, 여기서 실행하면 DB의 gCategory = "top" 데이터 출력 잘됩니다.package com.controller.main; import java.io.IOException; import java.util.List; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import com.dto.GoodsDTO; import com.service.GoodsService; @WebServlet("/main") public class MainServlet extends HttpServlet { private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String gCategory = request.getParameter("gCategory"); if(gCategory==null) gCategory = "top"; GoodsService service = new GoodsService(); List list = service.goodsList(gCategory); System.out.println(list.size()); request.setAttribute("goodsList", list); RequestDispatcher dis = request.getRequestDispatcher("main.jsp"); dis.forward(request, response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { doGet(request, response); } }그 WebContect/main.jsp <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> Insert title here <% String mesg = (String)session.getAttribute("memberAdd"); if(mesg!=null){ %> <% } %>

Main 화면입니다.

Webcontent/goods/goodsList.jsp<%@page import="com.dto.GoodsDTO"%> <%@page import="java.util.List"%> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>

<% List list = (List)request.getAttribute("goodsList"); for( int i = 0; i < list.size(); i++ ){ GoodsDTO dto = list.get(i); String gCode = dto.getgCode(); String gCategory = dto.getgCategory(); String gName = dto.getgName(); String gContent = dto.getgContent(); int gPrice = dto.getgPrice(); String gImage = dto.getgImage(); %> <% if(i%4==0){ %> <% }//end if %> <% }//end for %>

.gif" border="0" align="center" width="200">

<%= gName%>
--------------------

<%= gContent%>

<%= gPrice%>

at org.apache.jsp.goods.goodsList_jsp._jspService(goodsList_jsp.java:139) 를 톰캣 폴더에서 파일 찾아가보면 (goodsList_jsp.java:139)는 for문 도는 곳인데 뭐가 문제인지 모르겠습니다main.jsp 안 거치고, Servlet에서 바로 goodsList.jsp로 보내도 오류가 나네요고수님들 도움 부탁드립니다...

제타건담 · Answer

list 변수가 null 이어서 발생하는겁니다..null 이기 때문에 list.size() 실행시 NullpointerException 이 뜨는거구요..Servlet에서 goodsList.jsp로 보내도 오류가 발생한다면 Servlet에서 애초에 null이었을 가능성이 있습니다..한번 체크해보세요..

lemon08 · Answer

아이고 질문을 헷갈리게 썼었네요;;; 1. 서블릿에서 ctrl &#43; F11하면 list가 잘 나옵니다 2. main.jsp에서는 ctrl &#43; F11하면 list가 안나옵니다..

Mambo · Answer

자바에서 null에 대한 캐스팅을 오류를 내지 않아요. list.size 함수 호출 시 제타건담님이 말씀하신 것 처럼 list가 null 이므로 NullPointerException 오류가 발생하는 겁니다. 애초에 request.getAttriubute 결과가 null이 아닐거란 보장된 코드는 아닙니다.

org.apache.catalina.core.ApplicationDispatcher invoke 초보 개발자 도와주세요

3개의 답변

#nullpointerexception 목록