4. Learning response data and view the results of springmvc

A return value classification:

String: Returns the value of the view to be presented
void: return to the default page (method name .jsp)
ModleAndView: storage object and return to the Page Setup

1. String:

jsp:

1 <a href="/user/testString">response</a>

 1 <%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
 2 <html>
 3 <head>
 4     <title>success</title>
 5 </head>
 6 <body>
 7 <h3>执行成功</h3>
 8 
 9 ${user.username}
10 ${user.age}
11 </body>
12 </html>

控制器方法：

    /**
     * 返回值为需要展示的视图
     * @param model
     * @return
     */
    @RequestMapping("/testString")
    public String testString(Model model){

        System.out.println("testString执行了...");


        //模拟从数据库中查询出User对象
        User user = new User();
        user.setUsername("美美");
        user.setPassword("123");
        user.setAge(30);

        //设置model对象
        model.addAttribute("user",user);

        return "success";
    }

2.void

jsp:

 1 <%@ page contentType="text/html;charset=UTF-8" language="java" %>
 2 
 3 <html>
 4 <head>
 5     <title>response</title>
 6 </head>
 7 <body>
 8 
 9 <a href="/user/testString">testString</a>
10 <a href="/user/testVoid">testVoid</a>
11 </body>
12 </html>

方法：

 1     /**
 2      * void的返回值，会默认跳转到一个testVoid.jsp的页面下导致错误。
 3      * 我们可以使用
 4      * 1.请求转发：路径名为 "/WEB-INF/pages/success.jsp"
 5      * 2.重定向：路径名为 request.getContextPath()+"/success.jsp"
 6      *
 7      * @param request
 8      * @param response
 9      * @throws Exception
10      */
11     @RequestMapping("/testVoid")
12     public void testVoid(HttpServletRequest request, HttpServletResponse response) throws Exception {
13 
14         System.out.println("testVoid执行了...");
15 
16         //请求转发
17 //        request.getRequestDispatcher("/WEB-INF/pages/success.jsp").forward(request,response);
18 
19         //重定向
20 //        response.sendRedirect(request.getContextPath() + "/success.jsp");
21 
22         //直接响应
23         response.setCharacterEncoding("UTF-8");
24         response.setContentType("text/html;charset=UTF-8");
25 
26         response.getWriter().println("hello");
27 
28         return;
29     }

3.ModelAndView

jsp

1 <a href="/user/testModelAndView">testModelAndView</a>

方法：

 1     /**
 2      * 返回ModelAndView设置的页面
 3      * @return
 4      */
 5     @RequestMapping("/testModelAndView")
 6     public ModelAndView testModelAndView() {
 7 
 8         System.out.println("testModelAndView执行了...");
 9 
10         //创建ModelAndView对象
11         ModelAndView mv = new ModelAndView();
12 
13         User user = new User();
14         user.setUsername("美美");
15         user.setPassword("123");
16         user.setAge(30);
17 
18         //将user放入ModelAndView对象中，同时也会将user对象放入request对象中
19         mv.addObject("user", user);
20 
21         //设置跳转界面
22         mv.setViewName("success");
23 
24         return mv;
25     }

4. Learning response data and view the results of springmvc

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