Spring MVC : post request and json object with array : bad request

I'm trying to retrieve parameters from a http POST request with Spring MVC.

The request contains the following json object (content-type : application/json), which itself contains an array of customObjects :

{  
   "globalId":"338",
   "lines":[  
      {  
         "id": "someId",
         "lib":"blabla",
        ...

      }
   ]
}

Here's the code I'm trying to use :

  @RequestMapping(method = RequestMethod.POST, value = "/valider")
  @ResponseBody
  public void valider(final HttpServletRequest request, @RequestParam("globalId") final String globalId, @RequestParam("lines") final MyCustomObject[] lines) {

All I'm getting is a "bad request" error (http 400).

Is it possible to separately retrieve the two parameters "globalId" and "lines" ? Or since they are in the same json object, it has to be treated has a single parameter ? How do you proceed when you have more than one parameter in a Post request ?