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forward:hello 与 redirect:hello的区别

对于某些Controller的处理方法,当返回值为String类型时,返回的结果中可能含有forward或redirect前缀;

如:

 1 @Controller 2 @RequestMapping("/user") 3 public class UserController { 4     @RequestMapping("/forward") 5     public String replyWithForward(HttpServletRequest request, String userId){ 6         request.setAttribute("userid", userId); 7          8         System.out.println("userId =" +userId); 9         10         return "forward:hello";11     }12     13     @RequestMapping("/redirect")14     public String replyWithRedirect(HttpServletRequest request, String userId){15         request.setAttribute("userid", userId);16         17         System.out.println("userId = "+userId);18         19         return "redirect:hello";20     }21 }

测试页面hello.jsp:

 1 <%@ page language="java" contentType="text/html; charset=UTF-8" 2     pageEncoding="UTF-8"%> 3 <% 4      String userId = (String)request.getAttribute("userid");    5      System.out.println("获取到的userId为:"+userId); 6 %> 7 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> 8 <html> 9 <head>10 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">11 <title>测试页面</title>12 </head>13 <body>14     hello, <%= userId %>;15 </body>16 </html>

当路径为 http://localhost:8080/crazysnailweb/user/forward?userId=123时,浏览器中的URL不会发生变化,且页面输出:

      

 当路径为http://localhost:8080/crazysnailweb/user/redirect?userId=123 时,浏览器中URL变为http://localhost:8080/crazysnailweb/user/hello,且页面输出:

      

注:redirect会让浏览器发起一个新的请求,因而原来request对象中的参数丢失;而forward所到的目标地址位于当前请求中,request中的参数不会丢失;