Question

I have a Spring MVC controller with an action that’s called using AJAX.

@SessionAttributes({"userContext"})
public class Controller
{
    ...
    @RequestMapping(value = "/my-url", method= { RequestMethods.POST })
    public ModelAndView doSomething(@ModelAttribute("userContext") UserContext context,
            SessionStatus sessionStatus)
    {
        BusinessObject obj = doSomeBusinessLogic(context.getUserName());
        sessionStatus.setComplete();
        ModelAndView mav = new ModelAndView("jsonView");
        mav.addObject("someInt", obj.getId());
        return mav;
    }
}

When I run this action, I get the following exception:

net.sf.json.JSONException: There is a cycle in the hierarchy!
at t.sf.json.util.CycleDetectionStrategy$StrictCycleDetectionStrategy.handleRepeatedReferenceAsObject(CycleDetectionStrategy.java:97)
at net.sf.json.JSONObject._fromBean(JSONObject.java:833)
at net.sf.json.JSONObject.fromObject(JSONObject.java:168)
at org.springframework.web.servlet.view.json.writer.jsonlib.PropertyEditorRegistryValueProcessor.processObjectValue(PropertyEditorRegistryValueProcessor.java:127)
at net.sf.json.JSONObject._fromMap(JSONObject.java:1334)
Truncated. see log file for complete stacktrace

After doing some debugging I found out that Spring is placing the UserContext object onto the ModelAndView that I am returning. If I hard-code my user name and remove the context object from the method’s parameters, the action runs successfully. Is there a way to configure Spring to omit the ModelAttribute-annotated parameters from the returned ModelAndView? As you can see, sessionStatus.setComplete() has no effect.

Answer 1

I registered a WebArgumentResolver to get to my session variable. This allowed me to keep this session variable out of the response while keeping my action unit testable.