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How to do it...

To implement page redirection with Flash-scoped objects, apply these steps:

To start our experiment on implementing page redirection, let us create a controller that loads a login form, processes the username and password, and then redirects to another form controller through Spring's old way of page navigation, that is, through RedirectView:

@Controller 
public class RedirectPageController { 
  
  @RequestMapping(value="/login.html", 
       method=RequestMethod.GET) 
  public String login(){ 
    return "login"; 
  } 
  
  @RequestMapping(value="/jump_page.html",  
    method=RequestMethod.POST) 
  public RedirectView sendRedirection(RedirectAttributes  
   atts, @RequestParam("username") String username,      
         @RequestParam("password") String password){ 
 
    atts.addFlashAttribute("username", username); 
    atts.addFlashAttribute("password", password); 
    atts.addAttribute("request", "loginForm"); 
    return new RedirectView("/redirectviewOld.html",true); 
  } 
 
@RequestMapping(value="/redirectviewOld.html",  
  method=RequestMethod.GET) 
public String resultPageOld(Model model ){ 
    return "result_page"; 
  } 
}

The handler method uses org.springframework.web.servlet.mvc.support.RedirectAttributes to convert username and password parameters to Flash-scoped objects. Flash-scoped objects are capable of holding their values until the next redirected view is processed. Likewise, they can also pass typical request-scoped objects to success views.

Create the login form view with typical HTML textboxes and submit buttons:

<%@ page language="java" contentType="text/html;  
charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> 
<%@ taglib prefix="spring" uri="http://www.springframework.org/tags" %> 
<!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=ISO-8859-1"> 
<title><spring:message code="login_title" /></title> 
</head> 
<body> 
  <form action="/ch03/jump_page.html" method="POST"> 
    <spring:message code="userLbl" />&nbsp;&nbsp; 
    <input type="text" name="username" /><br/> 
    <spring:message code="passwordLbl" />&nbsp;&nbsp; 
    <input type="text" name="password" /><br/> 
    <input type="submit" value="Login" /> 
  </form> 
</body> 
</html>

Create the redirected page that will show on screen both the username and password Flash-scoped objects and a request-scoped one:

<%@ page language="java" contentType="text/html;charset=ISO-8859-1" 
pageEncoding="ISO-8859-1"%> 
<!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=ISO-8859-1"> 
<title>Insert title here</title> 
</head> 
<body> 
    User Name: ${ username } <br/> 
    Password: ${ password } <br/> 
    Requested by: ${ loginForm } 
</body> 
</html>

Update the views.properties and messages_en_US.properties for all the updates on the views and the view's message bundles.
Save all files and deploy the project. Open a browser and execute https://localhost:8443/ch03/login.html. Observe how the two Flash-scoped and a request-scoped data behave when in this form:

This submits to another form controller using page redirection:
Add the following request handlers that use a modern technique of implementing page redirection through the shorthand keyword redirect:

@RequestMapping(value="/new_jump.html", method=RequestMethod.GET) 
public ModelAndView sendRedirectionModel(ModelMap atts){ 
    atts.addAttribute("pageId_flash", "12345"); 
    return new ModelAndView( 
       "redirect:/redirectviewNew.html",atts); 
} 
  
@RequestMapping(value="/redirectviewNew.html", 
    method=RequestMethod.GET) 
public String resultPageNew(Model model, 
    @ModelAttribute("pageId_flash") String flash){ 
    model.addAttribute("pageId_flash", flash); 
    return "new_result_page"; 
}

There are three conditions expected to be met when using the prefix redirect, and one is the absence of RedirectAttributes for Flash-scoped object generation. Also, this technique is best paired with ModelAndView with regard to the transporting of objects to views. And lastly, the redirected handler method must have @ModelAttribute to fetch all objects passed by the originator request from which the redirection started.

Save all files. Then clean, build, and deploy the project. Run https://localhost:8443/ch03 /new_jump.html on a browser and expect this output: