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POPassing list from servlet to jsp null
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  1. POPassing list from servlet to jsp null
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    copied!<p>I am trying to retrieve values from a database based on a selection of dates the user makes in a JSP page. The user will select two dates and the database will be queried. </p> <p>In my Servlet i am doing this. The for statement tells me that the list has got values in which are correct.</p> <pre><code>VehiclesList list = dataManager.getVehiclesWhere(dateFrom, dateTo); request.setAttribute("vehiclesList", list); VehiclesList vList = (VehiclesList) request.getAttribute("vehiclesList"); for (int pos = 0; pos &lt; vList.size(); pos++) { Vehicles vehicles = vList.getVehicleAt(pos); System.out.println(vehicles.getC02Emissions()); System.out.println(vehicles.getManufacture()); System.out.println(vehicles.getRegNumber()); System.out.println(vehicles.getHireRate()); } RequestDispatcher dispatcher = request.getRequestDispatcher("/vehicles.jsp"); dispatcher.forward(request, response); </code></pre> <p>This is the code in my JSP page. I am doing the same process above, ie requesting the attribute, creating a new list and displaying the data, but the new list i am creating is coming out null and i am receiving a null pointer exception.</p> <pre><code>VehiclesList vList = new VehiclesList(); vList = (VehiclesList) request.getAttribute("vehiclesList"); for (int pos = 0; pos &lt; vList.size(); pos++) { Vehicles vehicle = vList.getVehicleAt(pos); System.out.println(vehicle.getC02Emissions()); } </code></pre> <p>Why is the list on the JSP side null, when on the servlet side it holds the correct values?</p> <p>EDIT-----</p> <p>This is my stacktrace.</p> <pre><code> WARNING: StandardWrapperValve[jsp]: PWC1406: Servlet.service() for servlet jsp threw exception java.lang.NullPointerException at org.apache.jsp.vehicles_jsp._jspService(vehicles_jsp.java from :257) at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:111) at javax.servlet.http.HttpServlet.service(HttpServlet.java:770) 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:770) at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1550) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655) at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:161) at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:331) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:231) at com.sun.enterprise.v3.services.impl.ContainerMapper$AdapterCallable.call(ContainerMapper.java:317) at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:195) at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:860) at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:757) at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1056) at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:229) at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104) at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90) at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79) at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54) at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59) at com.sun.grizzly.ContextTask.run(ContextTask.java:71) at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532) at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513) at java.lang.Thread.run(Thread.java:680) </code></pre> <p>EDIT 2------------</p> <p>Servlet code</p> <pre><code>package Oracle; import RentalRecords.Vehicles; import RentalRecords.VehiclesList; import java.io.IOException; import javax.servlet.RequestDispatcher; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; public class VehiclesServlet extends HttpServlet { private boolean dbOK = false;//boolean to check if data input is not null private Vehicles vehicle;//used to get user data from bean private DatabaseConnector dataManager;//used to interact with the database /** * * Initialises the servlet by creating a new DatabaseConnector object which * will be used to interface with the database */ public void init() { dataManager = new DatabaseConnector(); } public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { String dateFrom = request.getParameter("from");//get email submitted from form String dateTo = request.getParameter("to");//get password submitted from form System.out.println(dateFrom + dateTo); if (dateFrom != null || dateTo != null) { dbOK = true; } else { dbOK = false; }//end if HttpSession session = request.getSession(true);//set the session if (dbOK) { try { System.out.println(dbOK); VehiclesList list = dataManager.getVehiclesWhere(dateFrom, dateTo); request.getSession().setAttribute("vehiclesList", list); VehiclesList vList = (VehiclesList) request.getAttribute("vehiclesList"); for (int pos = 0; pos &lt; vList.size(); pos++) { Vehicles vehicles = vList.getVehicleAt(pos); System.out.println(vehicles.getC02Emissions()); System.out.println(vehicles.getManufacture()); System.out.println(vehicles.getRegNumber()); System.out.println(vehicles.getHireRate()); } RequestDispatcher dispatcher = request.getRequestDispatcher("/vehicles.jsp"); dispatcher.include(request, response); //request.getRequestDispatcher("vehicles.jsp").forward(request, response); } catch (Exception e) { e.printStackTrace(); }//end try } else { //User is not valid, redirect back to index.jsp and inform user session.setAttribute("signupError", "Signup Not Successful"); session.setAttribute("signupSuccess", null);//set this null if it is a resubmit System.out.println(session.getAttribute("signupError")); RequestDispatcher dispatcher = request.getRequestDispatcher("/vehicles.jsp"); dispatcher.forward(request, response); } } } </code></pre> <p>JSP Code</p> <pre><code>&lt;%@page import="RentalRecords.Vehicles"%&gt; &lt;%@page import="RentalRecords.VehiclesList"%&gt; &lt;%@page contentType="text/html" pageEncoding="UTF-8"%&gt; &lt;!DOCTYPE html&gt; &lt;html&gt; &lt;head&gt; &lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8"&gt; &lt;title&gt;JSP Page&lt;/title&gt; &lt;script&gt; $(document).ready(function() { var from = $( "#from" ).datepicker({ defaultDate: "+1w", changeMonth: true, numberOfMonths: 1, minDate: 0, dateFormat: 'd-M-y', onClose: function( selectedDate ) { $( "#to" ).datepicker( "option", "minDate", selectedDate ); } }); var to = $( "#to" ).datepicker({ defaultDate: "+1w", changeMonth: true, numberOfMonths: 1, minDate: 0, dateFormat: 'd-M-y', onClose: function( selectedDate ) { $( "#from" ).datepicker( "option", "maxDate", selectedDate ); } }); }); &lt;/script&gt; &lt;/head&gt; &lt;body&gt; &lt;form id="getdates" method="get" action="getdates"&gt; &lt;label for="from"&gt;From&lt;/label&gt; &lt;input type="text" id="from" name="from" /&gt; &lt;label for="to"&gt;to&lt;/label&gt; &lt;input type="text" id="to" name="to" /&gt; &lt;input id="submitdates" name="submitdates" type="submit" value="Search" /&gt; &lt;/form&gt; &lt;div class="header_01"&gt;Vehicles&lt;/div&gt; &lt;% VehiclesList vList = new VehiclesList(); vList = (VehiclesList) request.getSession().getAttribute("vehiclesList"); for (int pos = 0; pos &lt; vList.size(); pos++) { Vehicles vehicle = vList.getVehicleAt(pos); System.out.println(vehicle.getC02Emissions()); %&gt; &lt;table&gt; &lt;tr&gt; &lt;td class="label"&gt;&lt;label id="ltable" for="table"&gt;&lt;/label&gt; &lt;table&gt; &lt;tr&gt; &lt;td class="label"&gt;&lt;label id="lbodytype" for="transmission"&gt;Body Type&lt;/label&gt;&lt;/td&gt; &lt;td class="field"&gt;&lt;input id="bodytype" name="transmission" type="text" value="&lt;%= vehicle.getBodyType()%&gt;" maxlength="50" readonly/&gt;&lt;/td&gt; &lt;td class="status"&gt;&lt;/td&gt; &lt;/tr&gt; &lt;tr&gt; &lt;td class="label"&gt;&lt;label id="ltransmission" for="transmission"&gt;Transmission&lt;/label&gt;&lt;/td&gt; &lt;td class="field"&gt;&lt;input id="transmission" name="transmission" type="text" value="&lt;%= vehicle.getTransmission()%&gt;" maxlength="50" readonly/&gt;&lt;/td&gt; &lt;td class="status"&gt;&lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;/td&gt; &lt;/tr&gt; &lt;/table&gt; &lt;% }%&gt; &lt;/body&gt; &lt;/html&gt; </code></pre>
 

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