How to retain login information for subsequent use - html

Question

Im fairly new to programming in JSP and I am making this web application where users need to log-in. I've done the registration of users but I am having problems when users are logging-in.
The main problem I am having is that, even though a user is able to successfully log-in, the information from the login form is lost. I need to retain the login information so that I can access the user's information during his/her session using the web application.
Here is the code that I currently have:
index.jsp (this is where the login form is shown)
<form name="Login Form" action="login.jsp"><table>
<tbody>
<tr>
<td><input type="text" name="emaillogin" value="email"/></td>
<td><input type="text" name="passlogin" value="password"/></td>
</tr>
<tr>
<td colspan="2" align="RIGHT><input type="submit" value="login" name="Login"/></td>
</tr>
</tbody></table></form>
login.jsp (this performs checking whether the user is valid or not, and redirects it to the user homepage if valid)
<%!
String email = "";
String password = "";
%>
<%
List users = new ArrayList();
Class.forName("com.mysql.jdbc.Driver");
Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db", "root", "pass");
Statement stmt = con.createStatement();
ResultSet result = stmt.executeQuery("SELECT email,password FROM users");
while (result.next()) {
users.add(result.getString(1));
users.add(result.getString(2));
}
con.close();
email = request.getParameter("emaillogin");
password = request.getParameter("passlogin");
int hasUser = 0;
Iterator<String> it = users.iterator();
while (hasUser == 0 && it.hasNext()) {
if (email.equals(it.next()) && password.equals(it.next())) {
hasUser = 1;
}
}
if (hasUser == 1) {
response.sendRedirect("homepage.jsp");
} else {
response.sendRedirect("index.jsp");
}
%>
homepage.jsp (this is where the user is redirected to after logging in, showing his/her email address)
.
.
<% out.println("Logged in as: " + request.getParameter("email")); %>
.
.
The current problem is that, null value is what I am getting from homepage.jsp. How can I solve this problem?
Thank you!

Answer 1

First of all I'll say - Avoid Java code in Jsp. Don't use JSP and Scriptlets to perform database operations. Always use Servlets.
You can use Jsp implicit tags (actions), EL and JSTL tag lib to format or present the data.
As per your question, you have to use session object to store data in one page and use them on another page.

Answer 2

I agree with putting this code into a servlet. A quick and simple way to pass a parameter is to the following:
response.sendRedirect("homepage.jsp?email="+email);

Answer 3

First of all let me give a clarity on Request parameters. Usually, request parameters will be in scope of request. So when you ask them in "Login.jsp" it will give you the email, password and what ever the fields you supplied from form. But when you are sending redirect to home page, those parameters won't be carried. So, when you find the user name and password is correct/ valid place them in session. So that you don't have to pass parameters manually to any request. Instead you can directly take the user name from "session" object and display where ever you want. This would be there in session, till the end of that session.
int hasUser = 0;
Iterator<String> it = users.iterator();
while (hasUser == 0 && it.hasNext()) {
if (email.equals(it.next()) && password.equals(it.next())) {
hasUser = 1;
}
}
if (hasUser == 1) {
session.setAttribute("email", email);
response.sendRedirect("homepage.jsp");
} else {
response.sendRedirect("index.jsp");
}
Usually this would be the process in real time. Of course Java code is not recommended here to use. Use JSTl, EL tags instead. In homepage.jsp you can display the email by taking from session.
Of course its too late reply.I guess this might help somebody facing the same problem.