jsp跳转getRequestDispatcher()和sendRedirect()的区别

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>

My JSP 'index.jsp' starting page
<meta http-equiv="pragma" content="no-cache" />
<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="expires" content="0" />
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3" />
<meta http-equiv="description" content="This is my page" />
    <!--
        <link rel="stylesheet" type="text/css" href="styles.css">
    -->
<form action="servlet/session" method="post">
  用户名:<input type="text" name="username" />

  密码:<input type="password" name="password" />

  <input type="submit" />
  </form>

import java.io.IOException;
import java.io.PrintWriter;

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

public class session extends HttpServlet {

    /**
     * Constructor of the object.
     */
    public session() {
        super();
    }

    /**
     * Destruction of the servlet.

     */
    public void destroy() {
        super.destroy(); // Just puts "destroy" string in log
        // Put your code here
    }

    /**
     * The doGet method of the servlet.

     *
     * This method is called when a form has its tag value method equals to get.
     *
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doPost(request, response);
    }

    /**
     * The doPost method of the servlet.

     *
     * This method is called when a form has its tag value method equals to post.
     *
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String username = "";
        String password = "";
        username = request.getParameter("username");
        password = request.getParameter("password");
        HttpSession session = request.getSession();
        session.setAttribute("username", username);
        session.setAttribute("password", password);
        request.setAttribute("name", username);
        request.setAttribute("pwd", password);

        RequestDispatcher dis = request.getRequestDispatcher("/getsession.jsp");
        dis.forward(request, response);

        /*
        response.sendRedirect("http://localhost:8080/sessiontest/getsession.jsp");
        */
                //这个路径必须是这样写，而不能像上面的request.getRequestDispatcher那样使用相对路径
                //  而且要是使用response.sendRedirect的话在下面的session.jsp中不能通过request.getAttribute来获取request对象
                //因为前后使用的不是同一个request，但是session可以，因为session会一直存在直到用户关闭浏览器
    }

    /**
     * Initialization of the servlet.

     *
     * @throws ServletException if an error occurs
     */
    public void init() throws ServletException {
        // Put your code here
    }

}

<%@ page language="java" import="java.util.*" pageEncoding="GBK"%>
<% String path = request.getContextPath(); String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/"; %>

My JSP 'getsession.jsp' starting page

<meta http-equiv="pragma" content="no-cache" />
<meta http-equiv="cache-control" content="no-cache" />
<meta http-equiv="expires" content="0" />
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3" />
<meta http-equiv="description" content="This is my page" />
    <!--
        <link rel="stylesheet" type="text/css" href="styles.css">
    -->

  <%   out.print("");   String username = (String)session.getAttribute("username");  
String password = (String)session.getAttribute("password");  
String name = (String)request.getAttribute("name");  
String pwd = (String)request.getAttribute("pwd"); 
 out.println("username " + username + " password " +password);
 //如果上面是使用response.sendRedirect的话就不能获取到name和pwd  
 out.println("name " + name + "pwd "+ pwd);   
  %>