Spring MVC-@SessionAttributes和status.setComplete（）

Question

I'm facing a problem I don't really know how to solve. I am developing a Bug Tracker (learning purposes only). I have a page to create a new issue and one page to edit an issue. Both, for now, have their own controllers.

EditIssueController.java

@Controller
@RequestMapping(value = "/issues/{issueId}")
@SessionAttributes("issuePackage")
public class EditIssueController {

    @Autowired
    private IssueService issueService;

    [...]

    @ModelAttribute("issuePackage")
    public IssueTagEnvironment populateIssue (@PathVariable("issueId") Integer issueId) {

        IssueTagEnvironment issueTagEnv = new IssueTagEnvironment();
        issueTagEnv.setIssue(issueService.getIssueById(issueId));

        return issueTagEnv;
    }

    @InitBinder
    public void initBinder (WebDataBinder binder) {

        [...]
    }

    @RequestMapping(value = "/edit", method = RequestMethod.GET)
    public ModelAndView editIssue (@PathVariable("issueId") Integer issueId,
                                   @ModelAttribute("issuePackage") IssueTagEnvironment issuePackage) {

        ModelAndView mav = new ModelAndView("/issues/EditIssue");

        [...]

        IssueTagEnvironment issueTagEnv = new IssueTagEnvironment();
        issueTagEnv.setIssue(issueService.getIssueById(issueId));

        [...]
        mav.addObject("issuePackage", issueTagEnv);

        return mav;
    }

    @RequestMapping(value = "/edit", method = RequestMethod.POST)
    public String updateIssue (@ModelAttribute("issuePackage") IssueTagEnvironment issuePackage,
                               BindingResult result) {

        if (result.hasErrors() == true) {
            return "redirect:/issues/{issueId}/edit";
        }

        issueService.updateIssue(issuePackage.getIssue());

        return "redirect:/issues/{issueId}";
    }
}

CreateIssueController.java

@Controller
@SessionAttributes("issuePackage")
public class CreateIssueController {

    @Autowired
    private IssueService issueService;

    [...]

    @ModelAttribute("issuePackage")
    public IssueTagEnvironment populateNewIssue () {

        return new IssueTagEnvironment();
    }

    @InitBinder
    public void initBinder (WebDataBinder binder) {

        [...]
    }

    @RequestMapping(value = "/issues/CreateIssue", method = RequestMethod.GET)
    public ModelAndView createIssueGet (@ModelAttribute("issuePackage") IssueTagEnvironment issuePackage) {

        ModelAndView mav = new ModelAndView("/issues/CreateIssue");

        [...]

        issuePackage.getIssue().setReporter(SecurityUtils.getCurrentUser());

        return mav;
    }

    @RequestMapping(value = "/issues/CreateIssue", method = RequestMethod.POST)
    public String createIssuePost (@ModelAttribute("issuePackage") IssueTagEnvironment issuePackage,
                                   BindingResult result,
                                   SessionStatus status) {

        if (result.hasErrors() == true) {
            return "redirect:/issues/CreateIssue";
        }

        [...]

        issueService.createIssue(issuePackage.getIssue());

        status.setComplete();
        return "redirect:/issues/" + issuePackage.getIssue().getId();
    }

}

So far everything seems correct (and in indeed works). But here are the dragons:

• I am within an "edit" page changing data from an existing issue.
• Instead of submitting the changes I decide to press the "Go Back" button from the navigator.
• Right after that action (Go Back), I decide to create a new issue and... Here it is! The form to create a new issue isn't empty but filled with the information of the previous "edited-but-not-submitted" issue.

I understand what the problem is: The controller is not completing the session/status by executing status.setComplete() .

My question here is, how to solve this problem?

Thanks in advance to the community!

Answer 1

For your current example, it is easy to fix , just change createIssueGet method to :

public ModelAndView createIssueGet () {

    ModelAndView mav = new ModelAndView("/issues/CreateIssue");
    IssueTagEnvironment issuePackage = new IssueTagEnvironment();

    ModelAndView mav = new ModelAndView("/issues/CreateIssue");
    mav.addAttribute("issuePackage", issuePackage);

    [...]

    [...]
}

That way you are sure that you always use a fresh IssueTagEnvironment object in that controller. And Spring will put it in session as you put it in model.

But the problem still remains : if you do not properly call status.setComplete() , you leave in session an object that should not be there, and like you said dragons may be there

I stopped using @SessionAttributes for that reason, and only use a hidden field (for the id) and a Converter from the id to a full object using the service layer, hoping it should be in cache and does not hit the database. Not really nice, but not really worse than that.