Comment obtenir la valeur de la valeur de la boîte à sélection multiple dans une publication dans SpringMVC (exemple de code)

<form:form commandName="user" method="post">
     <c:forEach items="${deploys}" var="deploy" varStatus="deployStatus">
      <input type="checkbox" name="checkbox" value="${deploy.id}"/>${deploy.systemName}
      <br>
     </c:forEach>
     <spring:bind path="id">//实际存储的值，此处隐藏
      <p class="form-group" hidden>
       <form:input path="id" name="id" cssClass="form-control"></form:input>
      </p>
     </spring:bind>
     <spring:bind path="accessControl">//实际存储的值，此处隐藏
      <p class="form-group" hidden>
       <form:input path="accessControl" name="accessControl" cssClass="form-control"></form:input>
      </p>
     </spring:bind>
     <input type=&#39;button&#39; value=&#39;确定&#39; onclick="fun()"/>//调用脚本，给需要post的数据赋值
     <p class="form-group">
      <button type="submit" class="btn btn-primary">保存</button>
      <a class="btn btn-success pull-right" href="/user/list" rel="external nofollow" >返回</a>
     </p>
 </form:form>

<script type="text/javascript">
 function fun() {
  var boxes = document.getElementsByTagName("input");
//  var val = []
  var str = "";
  for (var i = 0; i < boxes.length; i++) {
   if (boxes[i].name == "checkbox" && boxes[i].checked == true) {
//    val.push(boxes[i].value);
    str += boxes[i].value + &#39;,&#39;;
   }
  }
  $("#accessControl").val(str)
//  alert(atr);
//  alert(val);
 }
</script>

 @RequestMapping(value = "editaccesscontrol", method = RequestMethod.POST) //后端方法，
 public String editAccessControlPost(User user,ModelMap model ) {//接收参数对象user
  userMapper.updateUserAccessControl(user);
  model.addAttribute("user",user);
  model.addAttribute("success", "权限修改成功");
  return "redirect:/user/editaccesscontrol?id="+user.getId();
 }