response.sendRedirect() 和 RequestDispatcher 区别？

pengwjeagles 2006-04-30 11:38:12

response.sendRedirect("index.jsp");

和
RequestDispatcher rd=request.getRequestDispatcher("/index.jsp");
rd.forward(request,response);

上面都可以在servlet里面跳转到 index.jsp页面。但是这两个语句有区别吗？

还有本人一直对context理解不好能解释一下
RequestDispatcher rd=request.getRequestDispatcher("/index.jsp");
和
RequestDispatcher rd=getServletContext().getRequestDispatcher();
之间又有什么区别呢？
上面两个问题忘大虾告知。回答后立马结帖。

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切换为时间正序

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swantt 2006-07-28

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还是比较模糊。

sdxlh007 2006-07-28

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sendRedirect 是重新定向页面
RequestDispacher 是转发页面
用RequestDispacher转发的页面可以将状态继续传送到需要的页面，
而用了sendRedirect则会将request中的数据都清空

rootcn 2006-07-28

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http://community.csdn.net/Expert/TopicView3.asp?id=4811629

pengwjeagles 2006-05-01

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第二个问题呢？

ymfhcn 2006-04-30

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可以理解为RequestDispatcher是服务器转发，转发后，链接是不动的，并且内存资原可以用

response.sendRedirect("index.jsp");为客户端转发，转发后，链接会变，并且，request.getAttribute()不能再用

samkuang 2006-04-30

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sendRedirect 是简单的跳转
RequestDispacher 是请求转发

package com.bjsxt.servlet; import com.bjsxt.entity.User; import com.bjsxt.service.UserService; import com.bjsxt.service.impl.UserServiceImpl; import javax.servlet.RequestDispatcher; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.*; import java.io.IOException; import java.net.URLEncoder; import java.sql.Date; import java.util.ArrayList; import java.util.Arrays; import java.util.List; public class UserServlet extends BaseServlet { // @Override // protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // //解决POST表单的中文乱码问题 // request.setCharacterEncoding("utf-8"); // //接收method属性的值 // String methodName = request.getParameter("method"); // // //根据method属性的值调用相应的方法 // if("login".equals(methodName)){ // this.login(request,response); // }else if("register".equals(methodName)){ // this.register(request,response); // }else if("logout".equals(methodName)){ // this.logout(request,response); // } // // } public void show(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //获取表单的数据 String userId = request.getParameter("userId"); if(userId == null){ userId = ""; } String strAge = request.getParameter("minAge"); int minAge = 0; try{ minAge = Integer.parseInt(strAge); //"12" "abc" }catch(NumberFormatException e){ e.printStackTrace(); } //调用业务层完成查询操作 UserService userService = new UserServiceImpl(); //List userList = userService.findAll(); List userList = userService.find(userId,minAge); //List userList = null; //List userList = new ArrayList(); //跳转到show.jsp显示数据 request.setAttribute("userId",userId); request.setAttribute("minAge",strAge); request.setAttribute("ulist",userList); request.getRequestDispatcher("/admin/show.jsp").forward(request,response); } public void logout(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //结束当前的session request.getSession().invalidate(); //跳转回登录页面 response.sendRedirect(request.getContextPath()+"/admin/login.jsp"); } public void register(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //request.setCharacterEncoding("utf-8"); //1.接收来自视图层的表单数据 String userId = request.getParameter("userId"); String realName = request.getParameter("realName"); String pwd = request.getParameter("pwd"); String rePwd = request.getParameter("repwd"); int age = Integer.parseInt(request.getParameter("age"));// "23" String [] hobbyArr = request.getParameterValues("hobby"); String strDate = request.getParameter("enterDate");//"1999-12-23" Date enterDate = Date.valueOf(strDate); //util.Date SimpleDateFormat //判断两次密码是否相同 if(pwd == null || !pwd.equals(rePwd)){ request.setAttribute("error","两次密码必须相同"); request.getRequestDispatcher("/admin/register.jsp").forward(request,response); return; } //2.调用业务层完成注册操作并返回结果 User user = new User(userId,realName,pwd,age, Arrays.toString(hobbyArr),enterDate); UserService userService = new UserServiceImpl(); int n = userService.register(user); //3.根据结果进行页面跳转 if(n>0){ response.sendRedirect(request.getContextPath()+"/admin/login.jsp"); }else{ request.setAttribute("error","注册失败"); request.getRequestDispatcher("/admin/register.jsp").forward(request,response); } } public void login(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //解决POST表单的中文乱码问题 //request.setCharacterEncoding("utf-8"); //获取用户名和密码 request 内建对象请求 String username = request.getParameter("username"); String password = request.getParameter("password"); String rememberme = request.getParameter("rememberme"); //调用下一层判断登录是否成功，并返回结果 //进行服务器端的表单验证 if(username ==null || "".equals(username)){ request.setAttribute("error","用户名不能为空JSP"); request.getRequestDispatcher("/admin/login.jsp").forward(request,response); return; } if (username.length()<=6){ request.setAttribute("error","用户名长度必须大于6JSP"); request.getRequestDispatcher("/admin/login.jsp").forward(request,response);//后面语句还会执行 return; //后面的语句不再执行 } // boolean flag = false;//默认失败 // if(username.indexOf("sxt")>=0 || username.contains("尚学堂")){ // flag = true; // } User user = null;//默认登录失败 // UserDao userDao = new UserDaoImpl(); // user = userDao.find(username,password); UserService userService = new UserServiceImpl(); user = userService.login(username,password); //userService.addOrder("shoppingCart"); //输出结果 if(user != null){ //登录成功才记住我 //1.办理会员卡 String username2 = URLEncoder.encode(username,"utf-8"); Cookie cookie1 = new Cookie("uname",username2); Cookie cookie2 = new Cookie("password",password); //2.指定会员卡的作用范围,默认范围是当前目录 /servlet/LoginServlet /admin/login.jsp //cookie1.setPath("/"); //当前服务器 cookie1.setPath("/myservlet2/"); //当前项目 cookie2.setPath("/myservlet2"); //3.指定会员卡的作用时间 if("yes".equals(rememberme)){ cookie1.setMaxAge(60*60*24*10); //默认的时间浏览器不关闭的时间；-1 表示一直有效 cookie2.setMaxAge(60*60*24*10); }else{ cookie1.setMaxAge(0); cookie2.setMaxAge(0); } //4.将会员卡带回家 response.addCookie(cookie1); response.addCookie(cookie2); //成功跳转到成功页面 //out.println("登录成功"); // /servlet/LoginServlet // /servlet/success.jsp // request.getRequestDispatcher("/admin/success.jsp").forward(request,response); HttpSession session = request.getSession(); // session.setAttribute("username",username); session.setAttribute("user",user); //response.sendRedirect("/myservlet2/admin/success.jsp"); //response.sendRedirect("https://www.bjsxt.com:443/news/11377.html"); //response.sendRedirect("http://localhost:8080/myservlet2/admin/success.jsp"); //response.sendRedirect("/myservlet2/admin/success.jsp"); //response.sendRedirect("/myservlet2/admin/success.jsp"); //response.sendRedirect(request.getContextPath()+"/admin/success.jsp"); //http://192.168.58.250:8080/myservlet2/servlet/LoginServlet //http://192.168.58.250:8080/myservlet2/admin/success.jsp //登录成功后，网站的访问人数+1 //1.获取当前的访问人数 ServletContext context = this.getServletContext(); Integer count2 = (Integer) context.getAttribute("count"); //2.人数+1 if(count2 == null){ //第一个用户 count2 = 1; }else{ count2++; } //3.再存放到application作用域中 context.setAttribute("count",count2); //http://192.168.58.250:8080/myservlet2/servlet/admin/success.jsp response.sendRedirect("../admin/success.jsp"); }else{ //失败跳转回登录页面 //out.println("登录失败"); request.setAttribute("error","用户名或者密码错误"); // RequestDispatcher rd = request.getRequestDispatcher("/admin/login.jsp"); // rd.forward(request,response); //RequestDispatcher rd = request.getRequestDispatcher("http://localhost:8080/myservlet2/admin/login.jsp"); //RequestDispatcher rd = request.getRequestDispatcher("/admin/login.jsp"); //http://192.168.58.250:8080/myservlet2/servlet/admin/login.jsp RequestDispatcher rd = request.getRequestDispatcher("../admin/login.jsp"); rd.forward(request,response); } } }

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