jspInit keeps object in memory for all browser requests

Question

My jsp web application takes input from html input and keep it in the memory with the press of the button, so actually i push the values in the memory and keeps it untill reset is pressed. The problem comes when i goto another machine and run that application, i get the same values that were entered by the previous user.

eg:

main.jsp has some input fields and when i click 'add' those values from html input is stored in memory objects, and is showed in the html inputs till the memory is not cleared.

Now from another machine, i access this application and go to jsp file, there i get prefilled html input boxes having same values.

I know it is caused by i initializing the class object inside jspInit() function.

I have made sample project to show you the problem.

Test.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
        <%@ page import="test.TestClass" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"     "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>

<%!
TestClass objTest;
public void jspInit()
{
    objTest = new TestClass();
 }
%>
<form action="Test.jsp">
value1: <input type="text" name="txtValue1" value="    <%out.print(objTest.value1);%>"/>
value2: <input type="text" name="txtValue2" value="    <%out.print(objTest.value2);%>"/>
<input type="submit" name="btnSubmit"/>
</form>

<%
if(request.getParameter("btnSubmit")!=null)
{
    String str1 = request.getParameter("txtValue1");
    String str2 = request.getParameter("txtValue2");
    objTest.add(str1, str2);
}
%>
</body>
</html>

TestClass.java

package test;

public class TestClass {

    public String value1 ="no value";
    public String value2 ="no value";
    public void add(String str1, String str2)
    {
        value1 = str1;
        value2 = str2;
    }
}

why am i not getting a new page everytime i go from a different machine.The jspInit() function makes the object static and all its values are retained.

I need this jspInit() function because i want to retain the values for that particular user so that when he refreshes the page the form values are not gone.

How can i make jspInit() to retain value only for that particular browser request. Also what other approaches i can use.

Also the actual application is very big, so if possible please suggest some workaround for this approach.

P.S: A newbie to jsp.

P.S: I know using scriptlets is not a good approach.

Thanks in advance.

score 1 · Answer 1 · edited May 23 '17 at 11:43

1

The jspInit method is common for all the threads of your servlet class. Its use is basically for getting database connections and reader writer objects for a common resource. Your requirement is for every individual client of your server (i.e. different machine), for this you must use session object to store the parameters or use a Java Bean object.

You can refer this for good knowledge.

edited May 23 '17 at 11:43

Community

1
1

answered Apr 07 '15 at 07:20

Brijesh Bhatt

3,810
3
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will the java bean object be available to the Jsp when we refresh the page. Means if i store some value in java bean object and then go to another page and come back to this one, or just refreshes the page, will it retain the values i stored earlier? – Nikhar Apr 07 '15 at 12:24
You have to store that bean object in session to use throughout the application flow. you can accept the answer if it helped.. – Brijesh Bhatt Apr 07 '15 at 12:27

score 0 · Answer 2 · answered Apr 07 '15 at 06:04

may be you want to use the session Object to store values related to each session.

You can add session attributes like this: session.setAttribute("IDxxx",1) and you can retrieve Objects from session like this int id= Integer.parseInt(session.getAttribute("IDxxx").toString())

For more on jsp implicit Objects see here and here and here

jspInit keeps object in memory for all browser requests

2 Answers2