关于重定向页面和请求转发页面的区别

重定向页面resp.sendRedirect(forword)会有2次响应，重定向的页面无法通过req.getParameter("username")获取到表单信息

请求转发页面只进行一次响应可以获取响应表单元素req.getParameter("username")

forword="/xxx.jsp";
   RequestDispatcher rd= req.getRequestDispatcher(forword);
   rd.forward(req, resp);

package com.iwb.servlet;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginServlet extends HttpServlet {

    /**
     * 
     */
    private static final long serialVersionUID = 1L;

    /*@Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        String userName=req.getParameter("uname");
        String password=req.getParameter("upwd");
        
        System.out.println("用户名=>"+userName);
        System.out.println("密码=>"+password);
    }*/

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("=======进入doGet方法========");
        doPost(req,resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("=======进入doPost方法========");
        String userName=req.getParameter("uname");
        String password=req.getParameter("upwd");
        
        System.out.println("用户名=>"+userName);
        System.out.println("密码=>"+password);
        String forword=null;
        if(userName.equals("iwb") && password.equals("iwb")){
            //请求转发
            forword="/success.jsp";
            RequestDispatcher rd= req.getRequestDispatcher(forword);
            rd.forward(req, resp);
            //重定向
            //resp.sendRedirect(req.getContextPath()+"/success.jsp");
        }else{
            //请求转发
            forword="/error.jsp";
            RequestDispatcher rd= req.getRequestDispatcher(forword);
            rd.forward(req, resp);
            //重定向
            //resp.sendRedirect(req.getContextPath()+"/error.jsp");
        }
    }

}