点击登录按钮后报错了，这是什么意思哦

java.lang.ClassCastException: org.apache.catalina.connector.RequestFacade cannot be cast to javax.servlet.GenericServlet
at servlet.EmailUserServlet.doPost(EmailUserServlet.java:56)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:110)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:498)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:1025)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:445)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1115)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
。分界线、。
<!--邮箱登录  -->
      <div id="emil" >       
       <p>
          <label >邮箱:</label>
          <input id="txtEmail" type="text" class="txt"/>
       </p>
       <p>
          <label>密码:</label>
          <input id="txtPwd" type="password" class="txt"/>
       </p>
       <p>
        <input type = "button" value = "注册" style="width:80px;font-size: 14px;" onclick="emillogin()">                  
          </p>
          <a href="index.jsp" id="back">返回首页</a>
       </p>        
       </div>  。
function emillogin(){
document.pay.action="EmailUserServlet";
        document.pay.submit();
}
。
package servlet;import java.io.IOException;
import java.io.PrintWriter;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.Date;import javax.servlet.GenericServlet;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;import jdbc.DBOper;/**
 * Servlet implementation class LoginServlet
 */
@WebServlet("/EmailUserServlet")
public class EmailUserServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;    /**
     * @see HttpServlet#HttpServlet()
     */
    public EmailUserServlet() {
        super();
        // TODO Auto-generated constructor stub
    }    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doPost(request,response);
    }    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset = UTF-8");
        PrintWriter out = response.getWriter();
        String email = request.getParameter("email");
        String password = request.getParameter("password");
        ServletContext ctx = ((GenericServlet) request).getServletContext();
        String server = ctx.getInitParameter("server");
        String dbname = ctx.getInitParameter("dbname");
        String dbuser = ctx.getInitParameter("dbuser");
        String dbpwd = ctx.getInitParameter("dbpwd");       
        DBOper db = new DBOper();
        db.getConn(server, dbname, dbuser, dbpwd);
        String sql = "SELECT email,password FROM emailuser WHERE email = ? AND password = ?";
        ResultSet rs = db.executeQuery(sql,new String[]{email,password});
        try {
            if(rs != null && rs.next()){
                HttpSession session = request.getSession();
                session.setAttribute("email",email);
                SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");
                String logtime = sdf.format(new Date()); 
                session.setAttribute("logtime",logtime);
                Cookie cookie = new Cookie("email",email);
                cookie.setMaxAge(60*60*24*30);
                response.addCookie(cookie);
                RequestDispatcher dispatcher = request.getRequestDispatcher("MainServlet");
                dispatcher.forward(request,response);
            }else{
                out.print("登录失败");
                out.print("<br><a href = 'login.jsp'>重新登陆</a>");
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }    public void init()throws ServletException {    }}