springboot系列:url重定向和转发

<dependency>
    <groupId>io.pebbletemplates</groupId>
    <artifactId>pebble-spring-boot-2-starter</artifactId>
    <version>3.0.5</version>
</dependency>

# application.properties file
pebble.prefix=/templates/
pebble.suffix=.html
pebble.content-type=text/html
pebble.cache=false
pebble.encoding=UTF-8
pebble.defaultLocale=null
pebble.strictVariables=false

@Controller
@RequestMapping("/")
public class DemoController {

    /*
     * forward 示例: 以字符串的形式构建目标url, url 需要加上 forward: 前缀
     * */
    @RequestMapping("/forwardTest1")
    public String forwardTest1() {
        return "forward:/forwardTarget?param1=v1&param2=v2";
    }


    /*
     * forward 示例: 使用 ModelAndView() 设置转发的目标url
     * */
    @RequestMapping("/forwardTest2")
    public ModelAndView forwardTest2() {
        ModelAndView mav=new ModelAndView("/forwardTarget"); // 绝对路径OK
        //ModelAndView mav=new ModelAndView("forwardTarget"); // 相对路径也OK
        mav.addObject("param1", "value1");
        mav.addObject("param2", "value2");
        return mav ;
    }

    @RequestMapping("/forwardTarget")
    public String forwardTargetView(Model model, @RequestParam("param1") String param1,
            @RequestParam("param2") String param2) {
        model.addAttribute("param1", param1);
        model.addAttribute("param2", param2);
        return "forwardTarget";
    }


    /*
     * redirect 目标有三种构建方式
     * 1. 使用 redirect: 前缀url方式构建目标url
     * 2. 使用 RedirectView 类型指定目标
     * 3. 使用 ModelAndView 类型指定目标, ModelAndView 视图名默认是forward, 所以对于redirect, 需要加上 redirect: 前缀
     * */
    @RequestMapping("/noParamRedirect")
    public RedirectView noParamTest() {
        RedirectView redirectTarget = new RedirectView();
        redirectTarget.setContextRelative(true);
        redirectTarget.setUrl("noParamTarget");
        return redirectTarget;
    }

    @RequestMapping("/noParamTarget")
    public String redirectTarget() {
        return "noParamTarget";
    }

    @RequestMapping("/withParamRedirect")
    public RedirectView withParamRedirect(RedirectAttributes redirectAttributes) {
        RedirectView redirectTarget = new RedirectView();
        redirectTarget.setContextRelative(true);
        redirectTarget.setUrl("withParamTarget");

        redirectAttributes.addAttribute("param1", "value1");
        redirectAttributes.addAttribute("param2", "value2");
        return redirectTarget;
    }

    @RequestMapping("/withParamTarget")
    public String withParamTarget(Model model, @RequestParam("param1") String param1,
            @RequestParam("param2") String param2) {
        model.addAttribute("param1", param1);
        model.addAttribute("param2", param2);
        return "withParamTarget";
    }

    @RequestMapping("/withFlashRedirect")
    public RedirectView withFlashTest(RedirectAttributes redirectAttributes) {
        RedirectView redirectTarget = new RedirectView();
        redirectTarget.setContextRelative(true);
        redirectTarget.setUrl("withFlashTarget");

        redirectAttributes.addAttribute("param", "value");
        redirectAttributes.addFlashAttribute("flashParam", "flashValue");
        return redirectTarget;
    }


    /*
     * redirectAttributes.addAttribute加的attr, 使用 @RequestParam()来fetch
     * redirectAttributes.addFlashAttribute()加的attr, 使用 @ModelAttribute()来fetch
     * */
    @RequestMapping("/withFlashTarget")
    public String withFlashTarget(Model model, @RequestParam("param") String param,
            @ModelAttribute("flashParam") String flashParam) {
        model.addAttribute("param", param);
        model.addAttribute("flashParam", flashParam);
        return "withFlashTarget";
    }



    @GetMapping("/input")
    public String input() {
        return "input";
    }

    /*
     * form 提交后, 如果form数据有问题, 使用redirectAttributes.addFlashAttribute()加上 flash message.
     * addFlashAttribute()可以是任意类型的数据(不局限在String等基本类型)
     * addFlashAttribute() 加的 attr, 不会出现在url 地址栏上.
     * addFlashAttribute() 加的 attr, 一旦fetch后, 就会自动清空, 非常适合 form 提交后 feedback Message.
     * */
    @PostMapping("/submit")
    public RedirectView submit(RedirectAttributes redirectAttributes) {
        boolean passed = false;
        if (passed==false) {
            RedirectView redirectTarget = new RedirectView();
            redirectTarget.setContextRelative(true);
            redirectTarget.setUrl("input");
            redirectAttributes.addFlashAttribute("errorMessage", "some error information here");
            return redirectTarget;
        }else {
            RedirectView redirectTarget = new RedirectView();
            redirectTarget.setContextRelative(true);
            redirectTarget.setUrl("inputOK");
            return redirectTarget;
        }
    }
}

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <meta name="description" content="">
    <meta name="author" content="">
    <title> </title>
    <link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-beta/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-/Y6pD6FV/Vv2HJnA6t+vslU6fwYXjCFtcEpHbNJ0lyAFsXTsjBbfaDjzALeQsN6M" crossorigin="anonymous">
    <link href="https://getbootstrap.com/docs/4.0/examples/signin/signin.css" rel="stylesheet" crossorigin="anonymous"/>
  </head>
  <body>
     <div class="container">
      <form class="form-signin" method="post" action="/submit">
        <h2 class="form-signin-heading">Please input</h2>
        {% if errorMessage is not empty %}
           <div class="alert alert-danger" role="alert">{{errorMessage}}</div>         
        {% endif %}   
        <p>
          <label for="username" class="sr-only">Username</label>
          <input type="text" id="username" name="username" class="form-control" placeholder="Username" required autofocus>
        </p>
        <button class="btn btn-lg btn-primary btn-block" type="submit">submit</button>
      </form>
    </div >
   </body>
</html>

<!DOCTYPE html>
<html lang="en">
  <head>
    <title> </title>
  </head>
  <body>
     <div class="container">
     <h1>inputOK</h1> 
    </div >
   </body>
</html>

<!DOCTYPE html>
<html lang="en">
  <head> 
    <title>{{param1}} &nbsp; {{param2}} </title> 
  </head>
  <body> 
      <h1>forwardTarget</h1>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
  <head> 
    <title>{{param1}} &nbsp; {{param2}} </title> 
  </head>
  <body> 
      <h1>withParamTarget</h1>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>{{systemName}} &nbsp; {{version}} </title>
  </head>
  <body> 
         <h1>noParamTarget</h1>
</body>
</html>

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>{{param}} &nbsp; {{flashParam}} </title> 
  </head>
  <body>
     <h1>withFlashTarget</h1>
</body>
</html>