<h3>Login</h3>
<hr>
<form  name="loginForm"
	   method=POST
	   action="/JSPSERVLET/SimpleController"	>
	   <input type="hidden" name="cmd" value="login">
	   Login:<br>
	   <input type="text"
	   name="login"
	   value=""> <br>
	   Password: <br>
	   <input type="password"
	   name="password"
	   value=""> <br>
	   <input type="submit" value="SUBMIT">
	   </form>

<servlet>
		<description>
		</description>
		<display-name>
		SimpleController</display-name>
		<servlet-name>SimpleController</servlet-name>
		<servlet- class >
		com.test.SimpleController</servlet- class >
	</servlet>
	<servlet-mapping>
		<servlet-name>SimpleController</servlet-name>
		<url-pattern>/Simplecontroller</url-pattern>
	</servlet-mapping> 

 import  java.io.IOException;
 import  javax.servlet.ServletException;
 import  javax.servlet.*;
 import  javax.servlet.http.HttpServletRequest;
 import  javax.servlet.http.HttpServletResponse;

  public   class  SimpleController  extends  javax.servlet.http.HttpServlet  implements  javax.servlet.Servlet {
	
	 private   static   final   long  serialVersionUID = 1L;

	 public  SimpleController() {
		 super ();
	}   	
	
	 protected   void  doGet(HttpServletRequest request, HttpServletResponse response)  throws  ServletException, IOException {
		performTask(request, response);
	}  	
	
	 protected   void  doPost(HttpServletRequest request, HttpServletResponse response)  throws  ServletException, IOException {
		performTask(request, response);
	} 
	
	 protected   void  performTask(HttpServletRequest request, HttpServletResponse response)
		 throws  ServletException, IOException {
		 try  {
			String cmd = request.getParameter("cmd");
			 if  ("login".equals("cmd")) {
				String login = request.getParameter("login");
				String password = request.getParameter("password");
				request.setAttribute("user",login);
				jump("/main.jsp", request, response);
			}
		}  catch (Throwable e) {
			e.printStackTrace();
			jumpError(e.toString(), request, response);
		}
	}
	
	 protected   void  jump(String url, HttpServletRequest request, HttpServletResponse response)  throws  ServletException, IOException {
		RequestDispatcher rd = getServletContext().getRequestDispatcher(url);
		rd.forward(request, response);
	}
	
	 protected   void  jumpError(String errorMessage,HttpServletRequest request, HttpServletResponse response)  throws  ServletException,IOException {
		request.setAttribute("errorMessage", errorMessage);
		jump("/error.jsp", request, response);
	}
}

<servlet-mapping>
		<servlet-name>SimpleController</servlet-name>
		<url-pattern>/SimpleController</url-pattern>
	</servlet-mapping>