HTTP method POST is not supported by this URL

I wrote this html file
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>Login</title>
</head>

<body>
<h1>Login</h1>

Please enter your username and password
<form action="/Ch05/Login" method="POST">
<p><input type="text" name="username" length="40">
<p><input type="password" name="password" length="40">
<p><input type="submit" value="Submit" >
</form>
</body>
</html>

and the java class which it calls is
package web;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class Login extends HttpServlet {
public void dopost(HttpServletRequest request, HttpServletResponse response)
{ String username = request.getParameter("username");
try {
response.setContentType("text/html");
PrintWriter writer = response.getWriter();
writer.println("<html><body>");
writer.println("Thank You, "+ username + ". You are now logged into the system.");
writer.println("</body></html>");
writer.close();
}catch (Exception e) {
e.printStackTrace();
}
}
}
but when I am deploying it it giving the error as

"HTTP method POST is not supported by this URL" can somebody explain this?

Check your casing.

Do you mean doPost or dopost? Do I need to redeploy after changing that?

How would the change be picked up if you don't?