JServ - Это с чего можно сказать начался проект Apache Jakarta помню ковырялся с ним в году 99-м, потом уж появился Tomcat.

import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class RequestParamExample extends HttpServlet {

public void doGet(HttpServletRequest request, HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
RequestDispatcher dispatcher = null;
if(isUserValud(getUserName(request), getPassword(request)){
dispatcher = request.getRequestDispatcher("/main.jsp");
}else{
dispatcher = request.getRequestDispatcher("/error.jsp");
}
if (dispatcher != null)
dispatcher.forward(request, response);
}

public void doPost(HttpServletRequest request, HttpServletResponse res)
throws IOException, ServletException
{
doGet(request, response);
}

private boolean isUserValid(String username, String pwd){
// ...
}

private String getUserName(HttpServletRequest request){
return request.getParameter("username");
}

private String getPassword(HttpServletRequest request){
return request.getParameter("password");
}
}