Re: JSP Object lifetime

"Dave" <>
Tue, 10 Oct 2006 20:32:32 GMT
"Manish Pandit" <> wrote in message

Can you paste the code you're using to test?

The JSP, under the hood is a servlet that runs in the servlet container
(tomcat or something of similar nature). All the variables that are
used in the JSP end up in that servlet. Now, based on how you declared
them, they end up at different places in that servlet (local variables
vs. class variables). The container manages the lifecycle of this

The objID value is retained when reloading the JSP page. This is taken from
thisPage bean and is clearly because thisPage stays alive across page
reloads. The confusing part is that the line:

PageBean thisPage = adminDataModel.getCampaignPageModel();

.... should re-initialise thisPage (it includes returns a "new" PageBean
object) when it's called.

My code is below:


<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1" %>
<%@ include file="include/common.jsp" %>
<%@ include file="include/commonPrivate.jsp" %>
<%@ page import="java.util.Vector" %>
<%@ page import="com.dgs.cccm.beans.*" %>
<jsp:useBean class="com.dgs.cccm.cont.admin.AdminDataModel"
id="adminDataModel" scope="page" />
<jsp:useBean class="com.dgs.cccm.cont.validator.AdminValidator"
id="validator" scope="page" />
<jsp:useBean class="com.dgs.cccm.db.DataProxyMSSQL" id="dataProxy"
scope="page" />
<jsp:useBean class="com.dgs.cccm.html.HTMLFormGenerator"
id="htmlFormGenerator" scope="page" />
<jsp:useBean class="com.dgs.cccm.html.HTMLComponentGenerator"
id="htmlComponentGenerator" scope="page" />
 /* Declare page variables */

 String pageTitle = "Campaign";
 String pageHeader = "Manage Campaign";
 String pageSubHeader = "Edit New Campaign";
 String pageFile = "campaign.jsp";
 int objID = 0;

 int pageMode = -1;

 Vector invalidFieldNames = null;
 Vector invalidFieldMessages = null;

 boolean isSubmitted = false;
 boolean isFormValid = false;

 /* Declare page methods */

 boolean getDataFromForm(HttpServletRequest request, PageBean thisPage) {
  thisPage.setFieldValue("Name", request.getParameter("Name"));

  return true;

 /* Initialising scriptlet */
 validator = new AdminValidator();
 PageBean thisPage = adminDataModel.getCampaignPageModel();

 /* lots of irrelevant code snipped from here */

objID = thisPage.getFieldValue("Campaign_ID")



<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<%@ include file="include/htmlHead.jsp" %>
<table width="980" border="0" cellspacing="0" cellpadding="0">
<tr><td><%@ include file="include/header.jsp" %></td></tr>
<table border=1 width="100%"><tr><td>
<h2><%=pageSubHeader%> (<%=objID%>)</h2>
<td width="300" align="right">
 if (pageMode == FORM_NEW) {
<a href="javascript: saveForm()">Save</a>
 } else if (pageMode == FORM_EDIT) {
<a href="javascript: saveForm()">Save</a>
 } else if (pageMode == FORM_VIEW) {
<a href="<%=pageFile %>?id=<%=objID%>&m=1">Edit</a>

 htmlComponentGenerator.getHTMLValidationList(invalidFieldMessages, out);
<form name="dataForm" id="dataForm" method="post" action="<%=pageFile %>">
<input type="hidden" name="isSubmitted" id="isSubmitted" value="1" />
<input type="hidden" name="m" id="m" value="<%=pageMode %>" />
 Vector groups = thisPage.getGroups();
 for (int x=0; x<groups.size(); x++) {
  GroupBean thisGroup = (GroupBean)groups.elementAt(x);
  htmlFormGenerator.getHTMLGroup(thisGroup, out, pageMode, 1);


<tr><td><%@ include file="include/footer.jsp" %></td></tr>

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