I am trying to create an online quiz application, and have set out all of my java classes to make the quiz, and tested them within the console to ensure they are outputting what I require.
However when I visit my C1Test.jsp page, whereby a quiz should be generated, I am getting a NullPointerException thrown by glassfish, and after doing a bit of googling, I am still unsure why.
The stack trace can be found below, as well as my C1Test.jsp source code. Any help would be much appreciated, this is my final year project for my Computer Science degree, and I am unable to make any progress until this is fixed.
Thanks in advance.
Info: Closing WebApplicationContext for namespace 'dispatcher-servlet'startup date [Tue Nov 24 16:32:38 GMT 2015]; parent: Root WebApplicationContext
Info: WebModule[null] ServletContext.log():Closing Spring root WebApplicationContext
Info: Closing Root WebApplicationContext: startup date [Tue Nov 24 16:32:37 GMT 2015]; root of context hierarchy
Warning: StandardWrapperValve[jsp]: Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException
at org.apache.jsp.C1Test_jsp._jspService(C1Test_jsp.java:101)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:411)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:473)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:377)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:790)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:415)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:561)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:56)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
at java.lang.Thread.run(Thread.java:745)
C1Test.jsp source code:
<%--
Document : C1 Test
Created on : Nov 5, 2015, 6:47:35 PM
Author : Joe Perkins
--%>
<%@ page language="java" import="Dissertation.*" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>C1 Test</title>
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</head>
<body>
<nav class="navbar navbar-inverse">
<div class="container-fluid">
<div class="navbar-header">
<a class="navbar-brand" href="HomePage.jsp">EduMath</a>
</div>
<div>
<ul class="nav navbar-nav">
<li><a href="Index.jsp">Home</a></li>
<li><a href="C1.jsp">C1 Revision</a></li>
<li><a href="C2.jsp">C2 Revision</a></li>
<li><a href="SkillsetDeveloper.jsp">Skillset Development</a></li>
<li><a href="About.jsp"> About</a></li>
</ul>
</div>
</div>
</nav>
<div class="container">
<div class="jumbotron">
<h1>C1 Revision Test</h1>
</div>
<div class="container">
<%
// Retrieve the current quiz question
int currQuestion = ((Exam)request.getSession().getAttribute("currentTest")).getCurrentQuestion();
System.out.println("Question No. " + currQuestion);
%>
Current Question ${sessionScope.quest.questionNo+1} / 10
<span>${sessionScope.quest.question}</span><br/><br/>
<form class ="form-horizontal" action="test" method="post">
<c:forEach var="choice" items="q${sessionScope.quest.questionOptions}" varStatus = "counter">
<input type="radio" name="answer" value="${counter.count}" >${choice} <br/>
</c:forEach> <br />
<%
if(currQuestion > 0)
{
%>
<input type="submit" name="action" value="previous"/>
<% } %>
<%
if(currQuestion < 19)
{
%>
<input type="submit" name="action" value ="next"/>
<% } %>
<input type="submit" name="action" value="Finish Exam"/>
</form>
</form>
</div>
</div>
</body>
</html>
Edit: Different from question flagged as possible duplicate, I understand the basis of a NullPointerException, however was more looking for general advice on how to identify where the NullPointer is coming from based off the stack trace, as well as how best to set a session attribute.
