Spring MVC @ModelAttribute data is always null when doing a $http.put from Angular

I'm using Spring MVC to create a RESTfull API that is used by an AngularJS client. The read is working fine but when I'm trying to PUT some data from the client to the server, the @ModelAttribute object has allways null data (the test object it self is not null).

I have looked with firebug at the request, and tha data is there.

Do I need to configure something in order to convert the json to the mapped model?

Here is the Controller:

@Controller
@RequestMapping("/test")
public class TestController {

    @SuppressWarnings("UnusedDeclaration")
    protected TestController() {
    }

    @RequestMapping(value = "data", method = RequestMethod.GET)
    @ResponseStatus(HttpStatus.OK)
    @ResponseBody
    public TestResource getTest(){
        TestResource resource = new TestResource();
        resource.setId(LinkBuilderUtil.linkTo(TestController.class).slash("1").withSelfRel());
        resource.setValue1("value1");
        resource.setValue2("value2");
        return resource;
    }

    @RequestMapping(value = "/update", method = RequestMethod.PUT)
    @ResponseStatus(HttpStatus.OK)
    @Transactional
    public void updateParty(@ModelAttribute TestResource test) {
            String str="xxx";
    }
}

And here is how I create the request:

    $scope.save = function () {
         var headers = { 'Content-Type':'application/json' };
         $http.put($scope.url, $scope.updatedJson, { headers: headers });      

The TestResource:

@JsonIgnoreProperties(ignoreUnknown = true)
public class TestResource {
    String value1;
    String value2;
    Link id;

    public TestResource(){
    }

    public TestResource(String id, String value1, String  value2){
        this.id = LinkBuilderUtil.linkTo(TestController.class).slash(id).withSelfRel();
        this.value1 = value1;
        this.value2 = value2;
    }

    public Link getId() {return id;}

    public String getValue1() {return value1;}

    public String getValue2() {return value2;}

    public void setValue1(String value1) {this.value1 = value1;}

    public void setValue2(String value2) {this.value2 = value2;}

    public void setId(Link id) {this.id = id;}
}

And the request data:

{
  "value1": "value1",
  "value2": "newValue",
  "id": {
    "rel": "self",
    "href": "http:\/\/localhost:8080\/cim\/test\/1",
    "variableNames": [],
    "variables": [],
    "templated": false
  }
}