I have a simple html page where different links will pass different parameters in the url to a servlet.
parameters are integers so I assumed a simpleint c = Integer.parseInt(request.getParameter("c") would do it. But I get this instead: java.lang.NumberFormatException: Cannot parse null string I dont understand why this happens, this approach seemed to work fine on a different project.
I tried restarting the server saving doing clean and build over and over, i simply cannot work out why this doesnt work.
<!DOCTYPE html>
<html>
<head>
<title>Síiskolai Ülésrend</title>
<link rel="icon" type="image/x-icon" href="Resources/favicon.png">
<link rel="stylesheet" href="style.css">
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body>
<h1>Üdvözöllek! Kérlek válassz turnust!</h1>
<a href="DaySelectorServlet?c=1">
<figure>
<img src="Resources/folder.png" alt="1. Turnus">
<figcaption>1. Turnus</figcaption>
</figure>
</a>
<a href="DaySelectorServlet?c=2">
<figure>
<img src="Resources/folder.png" alt="2. Turnus">
<figcaption>2. Turnus</figcaption>
</figure>
</a>
<a href="DaySelectorServlet?c=3">
<figure>
<img src="Resources/folder.png" alt="3. Turnus">
<figcaption>3. Turnus</figcaption>
</figure>
</a>
<a href="DaySelectorServlet?c=4">
<figure>
<img src="Resources/folder.png" alt="4. Turnus">
<figcaption>4. Turnus</figcaption>
</figure>
</a>
<a href="DaySelectorServlet?c=5">
<figure>
<img src="Resources/folder.png" alt="5. Turnus">
<figcaption>5. Turnus</figcaption>
</figure>
</a>
</body>
</html>
package servlets;
import jakarta.servlet.annotation.WebServlet;
import jakarta.servlet.http.HttpServlet;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletResponse;
import jakarta.servlet.http.HttpSession;
import java.io.IOException;
@WebServlet("/DaySelectorServlet")
public class DaySelectorServlet extends HttpServlet{
protected void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException{
int course = Integer.parseInt(request.getParameter("c"));
HttpSession session = request.getSession();
session.setAttribute("course", course);
response.sendRedirect("DaySelector.jsp");
}
}