Spring-MVC 3.1: Forwarding A Request From One Controller Function To Another

Question

I'm using Spring 3.1. I have a controller function that takes in a command object ( a data holder ) submitted via a FORM and does some processing :

@RequestMapping(value = "/results", method = RequestMethod.POST)
public String toResultsScreen(@ModelAttribute("ssdh") SearchScreenDataHolder ssdh,
                                  BindingResult bindingResult,    
                                  ModelMap model,                
                                  HttpSession session) {

    if (bindingResult.hasErrors()) {
        logger.debug("Error returning to /search screen");
        return "search";
    }

    netView = "results";

    // do stuff

    return nextView;         

} // end function

Some user would like to programmatically make GET links to obtain information from our site and I would like to set up another handler that would handle that request. It would create a new installation of that the command object ( ssdh ) and populate it with the parameters sent via the GET request. Then it would pass it on to the handler above. Something like this:

@RequestMapping(value = "/pubresult")
public String toPublicResultsScreen(ModelMap model,    
                                   HttpSession session,             
                                   @RequestParam (required=true) String LNAME,   
                                   @RequestParam (required=false)String FNAME){

    Search search = new Search(usertype);

    // Capture the search parameters sent by HTTP
    ssdh.setLast_name(LNAME);
    ssdh.setFirst_name(FNAME);

    // To Do:  "forward this data holder, ssdh to the controller function quoted first

    return nextView;         

} // end function

My question is how can I forward my command/data holder object to the first controller function such that I don't have to alter the code to the first controller function in any way?

Answer 1

You can use RedirectAttributes object which was introduced in Spring MVC 3.1 and populate it with data you want to keep for redirection. It called PRG (POST/Redirect/GET) pattern.

@RequestMapping(value="/saveUserDetails.action", method=RequestMethod.POST)
public String greetingsAction(@Validated User user,RedirectAttributes redirectAttributes){
    //setting attributes 
    redirectAttributes.addFlashAttribute("firstName", user.getFirstName());
    redirectAttributes.addFlashAttribute("lastName", user.getLastName())
    return "redirect:success.html";
} 

I wrote some technical article regarding how to use it. I believe it will give you more details:

http://www.tikalk.com/java/redirectattributes-new-feature-spring-mvc-31

Answer 2

You should be able to set the ssdh in a ModelAttribute and simply forward it back, this way, the RequestDispatcher should be able to map it back to the /results handler:

@RequestMapping(value = "/pubresult")
public String toPublicResultsScreen(ModelMap model,    
                                   HttpSession session,             
                                   @RequestParam (required=true) String LNAME,   
                                   @RequestParam (required=false)String FNAME, Model model){

  Search search = new Search(usertype);
  // Capture the search parameters sent by HTTP
  ssdh.setLast_name(LNAME);
  ssdh.setFirst_name(FNAME);
  model.addAttribute("ssdh", ssdh);

  return "forward:/results";         

}