val json: JsValue = Json.parse("""
    {
      "item": {
            "id" : "11111111",
            "name" : "box",
            "categories" : [{
                               "name" : "blue box",
                               "id" : "12345",
                           },
                           {
                               "name" : "fancy box",
                               "id" : "98765",
                           }]
              }
    }
    """)

//I define my class and reader for one category
    case class ItemCategory(id: Option[String], name: String)
    implicit val categoryRead: Reads[ItemCategory] = (
        (JsPath  "item"  "categories"  "id").readNullable[String] and
        (JsPath  "item"  "categories"  "name").read[String]
    )(ItemCategory.apply _)

    //I define my class and reader for one item
    case class MyItem(categories : Option[List[ItemCategory]], id : Option[String], name : Option[String])
    implicit val myItemRead: Reads[MyItem] = (
        (JsPath  "item"  "categories").readNullable[List[ItemCategory]] and
        (JsPath  "item"  "id").readNullable[String] and
        (JsPath  "item"  "name").readNullable[String]
    )(MyItem.apply _)

    //I then try to read :
    var item: JsResult[MyItem] = json.validate[MyItem](myItemRead)
    println(item)