How can I get an object out of the model in the controller with Spring MVC 3?

Question

I have a controller with a method that handles incoming GET data, stores some things in the model, and then redirects to another page that deals with these objects.

I can't seem to find any good way of getting the object stored in the first method back out of the model to use in the second method. How can I do this?

Here's the top of the controller:

@Controller
@RequestMapping("/reviews")
@SessionAttributes({"review", "externalReview"})
public class ReviewController {
    // [SNIP]
}

Here's the code that adds the objects I'm after to the model:

@RequestMapping(value="/new", params="UName", method=RequestMethod.GET)
public String newFormFromExternal(@ModelAttribute("externalReview") ExternalReview externalReview, Model model) throws IncompleteExternalException {
    // Convert the inbound external
    Review fromExternal = ExternalReviewUtil.reviewFromExternalReview(externalReview, externalDAO);

    // Add the externalReview to the session so we can look to see if we got a reviewee on the way in
    model.addAttribute("externalReview", externalReview);

    model.addAttribute("review", fromExternal);

    return "redirect:/reviews/newFromExternal";
}

Answer 1

You are in luck.

If you are using or have ability to update to the newly released Spring 3.1, you can make use of the newly scoped Flash variables.

http://static.springsource.org/spring/docs/3.1.0.RC1/spring-framework-reference/html/mvc.html#mvc-flash-attributes

If you can't use 3.1, you probably can implement the solution yourself. Essentially you want to capture the model object required to be present in the redirect, put in the session, and remove it once it is retrieved to keep your session from bloating.