How do i pass parameters from one page to the other

**megabull** · 09-04-2012, 07:12 AM

I have to pass a parameter as a value (which has been set using session.setAttribute) to a function. How should i do so. The point is that, it is displaying using session.getAttribute, but not passing as a string parameter. Any suggestions on how to do so

Here's the page

Java Code:

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@ page import="java.io.*" %>
<%@ page import="java.lang.*" %>

<!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>Thanks for logging in</title>
</head>
<body>
<%
out.println("Hi " +(session.getAttribute("username")) + " Hope you're having a great day");
%>
<p>
<form method="post" action="login.jsp">
<input type="hidden" name="user" value="session.Attribute("username")">
<p><button value="Edit Data" onclick="window.location = 'info.jsp'"> Edit Data </button>
</form>
</body>
</html>

**Tolls** · 09-04-2012, 09:57 AM

What are you seeing and what are you expecting to see?
What class is the attribute referenced by "username"?

**wsaryada** · 09-04-2012, 10:13 AM

You should use a JSP expression get value from the session object before setting it as a value of the HTML input. For example:

Java Code:

<input type="hidden" name="user" value="<%= session.getAttribute("username") %>">

**Tolls** · 09-04-2012, 10:40 AM

Ohhhhh!
I didn't even see the hidden field (which is slightly ironic)...

**megabull** · 09-04-2012, 10:44 AM

@tolls : yes, "username' a session value that i've declared in the previous jsp page(which leads to this page that whose code you're seeing) using session.setAttribute . I'm trying to receive that and put it to some use. Actually, i need this value to match it with another variable.
Should i mention, on line 14, session.getAttribute("username") displays the correct value. The line 18 one passes 'null'. That's when i realized am not able to pass this as a parameter.

@wsaryada : <% %> Doesnt help. Tried it. Though i tried <%= as u suggested, caused an error.

The reason i chose session.setAttribute and session.getAttribute was that it wouldn't change for the session, so no issue.

**wsaryada** · 09-04-2012, 10:48 AM

Are you sure it doesn't work? <%= session.getAttribute("username") %>. With no no semicolon at the end.

If you use a scriptlet it should be something like:

Java Code:

<input type="hidden" name="user" value="<% out.print(session.getAttribute("username"); %>"/>

Or you can also use an EL (Expression Language)

Java Code:

<input type="hidden" name="user" value="${sessionScope["username"]}"/>

If error, what was the error message?

**megabull** · 09-04-2012, 10:59 AM

@wsaryada: Absolutely. Doesnt work. though the error was a one time show, the parameter value still shows 'null'. This page above redirects to info.jsp. Even there it shows 'null'. Here's the code for the line in info.jsp

Java Code:

System.out.println(session.getAttribute("username"));

Java Code:

ResultSet rs = s.executeQuery( "select * from userdata where id='"+ session.getAttribute("username") +"';");

Though there are no errors, the value being passed is 'null'

**wsaryada** · 09-04-2012, 11:29 AM

Do you mean the redirect to info.jsp is by pressing the Edit Data button on your page? This button is not submitting your form. So the value of name field will not be submitted. You are simply change the url to info.jsp. And also have you check that the session has a username attribute?

**megabull** · 09-04-2012, 12:09 PM

Hey. i found the problem. Its with <% session.invalidate(); %>; . I had a button to invalidate session. I never thought that inspite of being within a javascript onClick action, <% session.invalidate(); %>; would execute as soon as it is read.

Thanks for your time guys :)

**Tolls** · 09-04-2012, 01:39 PM

The Java stuff executes onthe server.
It is not affected by Javascript at all (or anything on the client).
All you said to the server by putting in <% session.invalidate(); %> in the JSP is "at this point of processing the JSP page invalidate the session".