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：
@Controller
@RequestMapping("/user")
public class UserController {
@RequestMapping("/forward")
public String replyWithForward(HttpServletRequest request, String userId){
request.setAttribute("userid", userId); System.out.println("userId =" +userId); return "forward:hello";
} @RequestMapping("/redirect")
public String replyWithRedirect(HttpServletRequest request, String userId){
request.setAttribute("userid", userId); System.out.println("userId = "+userId); return "redirect:hello";
}
}
测试页面hello.jsp：
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%
String userId = (String)request.getAttribute("userid");
System.out.println("获取到的userId为："+userId);
%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>测试页面</title>
</head>
<body>
hello, <%= userId %>;
</body>
</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；