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  1. 12-08-2010, 08:26 AM #1
    Rohit Pokhrel
    Rohit Pokhrel is offline Member
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    Post Accessing session variable from Java Class

    Dear all,
    I am having problem while accessing session variable from Java Class.

    -------index.jsp--------
    In index.jsp i am Creating session variable SCHEMA and assigning it value "SC0001"
    and finally redirecting to another jsp page Main_page.jsp

    Java Code: 
    <%@ page language="java" contentType="text/html; charset=utf-8"	pageEncoding="utf-8"%>
<%
session.setAttribute("SCHEMA","SC0001");
response.sendRedirect("Main_page.jsp");
%>

    -----Main_page.jsp----------
    In this page i am trying to fetch session information stored through previous page .I am using my class session() to access the session variable; Here i am facing problem which says java.lang.NullPointerException..

    Java Code: 
    <%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page  language="java" import = "MySession.*"%>
<html>
    <head>
       <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>Session Test</title>
    </head>
    <body>
     
       <h1><%
        session mysess=new session();
        try{
        String sesval=mysess.SessionTest();
        out.println("<b>Schema is --" + sesval + "</b>");
        }
        catch(Exception e)
                {
           out.println("<b>" + e + "</b>");
}        %>  </h1>
    </body>
</html>
    -------session.java-------------

    Java Code: 
    package MySession;
import javax.servlet.http.*;

public class session {

    private HttpServletRequest request;
    private HttpSession session;
    public String SessionTest() {
    
            session = request.getSession(true);

            String Schema=(String)session.getAttribute("SCHEMA");
            return  Schema;

}
}
    -----------
    please advise.

    thanks,
    Rohit
    Last edited by Rohit Pokhrel; 12-08-2010 at 11:01 AM.
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  2. 12-08-2010, 09:09 AM #2
    Tolls
    Tolls is offline Moderator
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    How does your session class (it should start with a capital letter by the way) get the current request? Clearly it isn't (hence the NPE).

    In the constructor for session pass in the request.

    ETA: As a general note, JSPs really shouldn't be forwarding or redirecting. They are for display, not flow control or business logic. That's what a Servlet is for.
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  3. 12-08-2010, 09:50 AM #3
    Rohit Pokhrel
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    Quote Originally Posted by Tolls View Post
    How does your session class (it should start with a capital letter by the way) get the current request? Clearly it isn't (hence the NPE).

    In the constructor for session pass in the request.

    ETA: As a general note, JSPs really shouldn't be forwarding or redirecting. They are for display, not flow control or business logic. That's what a Servlet is for.
    Thanks Tolls , As per your comment I have Changed my class to start with capital letter and as well I have merged my index.jsp with Main_page.jsp so that JSP is not redirecting any more. PLease have a look at modified Main_page.jsp

    Java Code: 
    <%@page contentType="text/html" pageEncoding="UTF-8"%>
<%@page  language="java" import = "Excel.*"%>
<%
session.setAttribute("SCHEMA","SC0001");
%>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
        <h1>

        <%
               //Retrieving attributes in Normal way.
              String Schema = (String)session.getAttribute("SCHEMA");
              out.println("<b>" + Schema + "</b>");

              //Retriving attributes using Session Class..
              Session mysess=new Session();
              try{
                   String sesval=mysess.SessionTest();
                  //String Schema = (String)session.getAttribute("SCHEMA");
                  out.println("<b>" + sesval + "</b>");
                  }
                catch(Exception e)
                {
                   out.println("<b>" + e + "</b>");
                }
        %>

      </h1>
    </body>
</html>
    -----
    Output:SC0001 java.lang.NullPointerException
    -----
    Can we actually read session variable attributes through Class file and return it to JSP ?
    Last edited by Rohit Pokhrel; 12-08-2010 at 11:00 AM.
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  4. 12-08-2010, 10:06 AM #4
    Tolls
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    Your Session is still trying to get data from an HttpRequest object that is null.
    I have no idea what you're trying to achieve here with your Session class.

    And please use code tags.
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  5. 12-08-2010, 04:07 PM #5
    mi14chal
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    Why don't you use bean? Look here: JSP Tutorial
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