ModelAttribute注解使用与spring重定向传参

@ModelAttribute可以用于修饰controller里的方法和参数，将被修饰的对象的值绑定到指定名称的属性里。
当修饰方法时，方法返回的值会在该controller里每个访问处理前绑定一次。
修饰参数时，如果想重定向或者转发到另一个方法后，还能在另一个方法中取得model里的参数值，可以使用两种方法（假设方法A里跳到方法B，要取得方法A里的参数）：

1.将方法A里的参数放在RedirectAttributes里，使用重定向进到B方法，在方法B里获取参数。

2.使用forward转发到B，使用HttpServletRequest.getAttribute()方法获取参数。

测试代码：

 @Controller

 @RequestMapping("/")

 public class ModelTest {

     @Value("wj")

     private String userName;

     @ModelAttribute("sayHello")

     public String runBeforeEachHandlerCalled() {

         System.out.println("runBeforeEachHandlerCalled方法执行");

         String sayHello = "Hello " + userName;

         return sayHello;

     }

     @RequestMapping(value = "/home",method = RequestMethod.GET)

     public String toHomePage() {

        return "index";

     }

     @RequestMapping(value = "/handler1")

     public String redirectMethod(@ModelAttribute("key2")String key2, RedirectAttributes attrbs) {

         System.out.println("handler1里");

         key2 = "key2value";

         attrbs.addAttribute("redirectAttr1","redirectAttr1value");

         attrbs.addFlashAttribute("redirectAttr2","redirectAttr2value");

 //       return "forward:/handler2";

 //       return new RedirectView("handler2");

         return "redirect:handler2";

     }

     @RequestMapping(value = "/handler2")

     public String redirectDestination(ModelMap map, String redirectAttr1,

                                       @ModelAttribute("redirectAttr2")String redirectAttr2,

                                       HttpServletRequest request, RedirectAttributes attrbs) {

         System.out.println("handler2里");

         System.out.println("ModelMap.key2值为：" + map.get("key2"));

         System.out.println("redirect.request.key2:" + request.getAttribute("key2"));

         System.out.println("redirect.request.redirectAttr1:" + request.getAttribute("redirectAttr1"));

         System.out.println("redirectAttr1值为：" + redirectAttr1);

         System.out.println("redirectAttr2值为：" + redirectAttr2);

         map.put("key3","key3value");

         attrbs.addAttribute("key4","key4value");

         return "forward:handler3";

     }

     @RequestMapping(value = "/handler3")

     public String forwardDestination(ModelMap map,@ModelAttribute("redirectAttr1") String redirectAttr1,

                                      @ModelAttribute("redirectAttr2")String redirectAttr2,@ModelAttribute("key4")String key4,

                                       HttpServletRequest request) {

         System.out.println("handler3里");

         System.out.println("ModelMap.key3值为：" + map.get("key3"));

         System.out.println("forward.request.key3:" + request.getAttribute("key3"));

         System.out.println("forward.request.redirectAttr1:" + request.getAttribute("redirectAttr1"));

         System.out.println("redirectAttr1值为：" + redirectAttr1);

         System.out.println("redirectAttr2值为：" + redirectAttr2);

         System.out.println("key4值为：" + key4);

         return "index";

     }

 }

index.jsp：

<%@ page language="java" contentType="text/html; charset=utf-8"

         pageEncoding="utf-8"%>

<html>

<body>

<h2>${sayHello}</h2>

</body>

</html>

输出：

runBeforeEachHandlerCalled方法执行

handler1里

runBeforeEachHandlerCalled方法执行

handler2里

ModelMap.key2值为：null

redirect.request.key2:null

redirect.request.redirectAttr1:null

redirectAttr1值为：redirectAttr1value

redirectAttr2值为：redirectAttr2value

runBeforeEachHandlerCalled方法执行

handler3里

ModelMap.key3值为：null

forward.request.key3:key3value

forward.request.redirectAttr1:null

redirectAttr1值为：redirectAttr1value

redirectAttr2值为：redirectAttr2value

key4值为：

巴特西

ModelAttribute注解使用与spring重定向传参

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