Is there a way to assign the value of a textfield to a session attribute in JSP prior to rendering?

Question

Is there a way to assign the value of a textfield to a session attribute in JSP prior to rendering?

Imagine I have the following code snippet:

<html>
<head>
    <script>
        function setSession()
        {
            var roll=document.getElementById("rollno").value;
            session.setAttribute("rollno", roll);
        }
    </script>
</head>
<body>
    <form action="process.jsp">
        RollNO: <input type="text" name="rollno" id="rollno" onblur=setSession()>
        Admission no <input type="text" name="anum" id="anum">
        <input  type="submit" value="Next"/>
    </form>
</body>
</html>

I am looking for an alternative solution to setting a session attribute when input is entered into the text field before form submission. Is there another way to store this information without submitting the form?

javascript html css ajax jsp

Answer 1

Answer №1

It's not possible to achieve your goal directly as the user session is not maintained on the client side after the JSP page rendering, due to HTTP being a stateless protocol.

A common solution is to use a Servlet to handle session data. By submitting your form to this servlet using a POST request, you can access the HttpSession from the HttpRequest parameter in the doPost method and store your variable there. You can then redirect the client to a target JSP page with a GET request.

If you prefer to avoid form submission, AJAX can be used. For example, jQuery's $.ajax function:

var params = {
    rollno: document.getElementById("rollno").value
};
$.ajax({
    url: 'myServlet?' + $.param(params),
    type: 'post'
});

The servlet implementation would look like this:

@WebServlet(name="myServlet", urlPatterns={"/myServlet"})
public class MyServlet extends HttpServlet {
    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse resp) {
        HttpSession session = req.getSession();
        // store the request parameter in the session
        session.setAttribute("rollno", req.getParameter("rollno"));
        // redirect user if not using AJAX
        // resp.sendRedirect("myOtherPage.jsp");
    } 
}

Answer 2

It's not possible to achieve your goal directly as the user session is not maintained on the client side after the JSP page rendering, due to HTTP being a stateless protocol.

A common solution is to use a Servlet to handle session data. By submitting your form to this servlet using a POST request, you can access the HttpSession from the HttpRequest parameter in the doPost method and store your variable there. You can then redirect the client to a target JSP page with a GET request.

If you prefer to avoid form submission, AJAX can be used. For example, jQuery's $.ajax function:

var params = {
    rollno: document.getElementById("rollno").value
};
$.ajax({
    url: 'myServlet?' + $.param(params),
    type: 'post'
});

The servlet implementation would look like this:

@WebServlet(name="myServlet", urlPatterns={"/myServlet"})
public class MyServlet extends HttpServlet {
    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse resp) {
        HttpSession session = req.getSession();
        // store the request parameter in the session
        session.setAttribute("rollno", req.getParameter("rollno"));
        // redirect user if not using AJAX
        // resp.sendRedirect("myOtherPage.jsp");
    } 
}

Answer 3

Answer №2

Easiest method to configure a servlet without the need to submit/render a form directly using the servlet.

Sample code snippet for creating a TextField:

Roll Number: <input type="text" name="rollno" id="rollno" onblur="setSession(this.value)">

Javascript code for the file that contains the textfield:

function setSession(roll)
{   
    var req = getRequestObject();
    req.onreadystatechange = function(){ handleServerResponse(req); };
    req.open("GET", "set_session.jsp?rollno=" + roll, true);
    req.send(null);   
}

function handleServerResponse(req)
{ 
    if(req.readyState == 4)
    {
        alert("Session has been successfully established.");
    }
}

function getRequestObject()
{
    if(window.XMLHttpRequest)
    {
        return(new XMLHttpRequest());
    }
    else if(window.ActiveXObject)
    {
        return(new ActiveXObject("Microsoft.XMLHTTP"));
    }
    else
    {
        return(null);
    }
}

Contents of file set_session.jsp:

<%
    String rollno = request.getParameter("rollno");
    session.setAttribute("roll", rollno);
%>

Answer 4

Easiest method to configure a servlet without the need to submit/render a form directly using the servlet.

Sample code snippet for creating a TextField:

Roll Number: <input type="text" name="rollno" id="rollno" onblur="setSession(this.value)">

Javascript code for the file that contains the textfield:

function setSession(roll)
{   
    var req = getRequestObject();
    req.onreadystatechange = function(){ handleServerResponse(req); };
    req.open("GET", "set_session.jsp?rollno=" + roll, true);
    req.send(null);   
}

function handleServerResponse(req)
{ 
    if(req.readyState == 4)
    {
        alert("Session has been successfully established.");
    }
}

function getRequestObject()
{
    if(window.XMLHttpRequest)
    {
        return(new XMLHttpRequest());
    }
    else if(window.ActiveXObject)
    {
        return(new ActiveXObject("Microsoft.XMLHTTP"));
    }
    else
    {
        return(null);
    }
}

Contents of file set_session.jsp:

<%
    String rollno = request.getParameter("rollno");
    session.setAttribute("roll", rollno);
%>

Is there a way to assign the value of a textfield to a session attribute in JSP prior to rendering?

Answer №1

Answer №2

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