Spring MVC Controller adds request object to response

I am building a JSON REST service with Spring 3.0.5 and my response contains the object from my request although I did not add it. I am using the MappingJacksonJsonView and Jackson 1.6.4 for rendering the ModelAndView object to JSON.

The User object is simple

public class SimpleUser {
    private String username;
    private String password;

    public String getUsername() { return username; }
    public void setUsername(String username) { this.username = username; }
    public String getPassword() { return password; }
    public void setPassword(String password) { this.password = password;
    }
}

One of the requests looks like this

@RequestMapping(value = "/register", method = RequestMethod.GET)
public ModelAndView register(SimpleUser user) {
    ModelAndView mav = new ModelAndView();
    mav.addObject("ok", "success");
    return mav;
}

Then I call the service with

curl 'http://localhost:8080/register?username=mike&password=mike'

The response I expect is

{"ok": "success"}

The response I get is

{"ok":"success","simpleUser":{"username":"mike","password":"mike"}}

Where and why is the user object added to the ModelAndView and how can I prevent that?

Possible solution

One way to work around this is to use Model instead of SimpleUser. This seems to work but it should be possible to use the busines开发者_如何学JAVAs object.

This works:

@RequestMapping(value = "/register", method = RequestMethod.GET)
public ModelAndView register(Model model) {
    log.debug("register(%s,%s)", model.asMap().get("usernmae"), model.asMap().get("password"));
    ModelAndView mav = new ModelAndView();
    mav.addObject("ok", "success");
    return mav;
}

It looks like you're trying to process a form submission and retrieve the result via ajax. If this is the case, you don't want to return a ModelAndView object. Use the @ResponseBody annotation to have Jackson represent your return object as a json object.

public @ResponseBody Map registerUser(SimpleUser user){
     Map responseMap = new HashMap();
     if(registerUser(user)){
          responseMap.put("OK", "Success");
     } else {
          responseMap.put("OK", "Failure");
     }
     return responseMap;
}

For Spring 3.1.x You can set the modelKey property in org.springframework.web.servlet.view.json.MappingJacksonJsonView in your *servlet.xml like below:

Servlet.xml:

<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView">
       <property name="modelKey" value="appResponse"/>
</bean>

Request Method:

@RequestMapping(value="/access") 
public @ResponseBody Model getAccess(Model model) {

  ...
  model.addAttribute("appResponse", responseDetails);
  ...

  return model;
}

When you set a specific modelKey, all other attributes attached the the model will be ignored, hence the form parameters/request parameters. In additional, this provides a clearer design if your are presenting views for multiple media types (application/xml or application/json).