maintain state with spring between requests

Question

I am new to spring so sorry if this is a beginners question, but the manual is not clear (at least not for me)

My question is: how do I share state between requests in spring? I can send data from the controller to the view by using a ModelMap, but the data in the ModelMap is not sent back to the next controller by the view. How can I do this with spring?

Below is a part of my source code. In the second controller the modelMap doesn't contain the data I stored in the modelMap in the first controller. How am I supposed to maintain state between controllers in spring?

thanks a lot for help.

@RequestMapping(value = "find/something", method = RequestMethod.GET)
public String foo(@RequestParam("parent") Parent parent, ModelMap modelMap) {    
...
    modelMap.addAttribute("question_index", 42);
    modelMap.addAttribute("something", new Something());
    modelMap.addAttribute("data", new Data());
    return "some/view";
}

<form:form action="bla" method="POST"  modelAttribute="data">
...// using Something() and 42
</form:form>

@RequestMapping(value = "bla", method = RequestMethod.POST)    
public String bla(@ModelAttribute("data") Data data, BindingResult result, ModelMap modelMap) {
System.out.println(modelMap); // doesn't contain question_index, or something
}

Answer 1

You can either put the modelMap in the HttpSession, or (preferable for larger applications), use Spring web flow where you can have the so called conversations.