title: Form binding back with List of multiple select options
body: <p>I'am trying to bind model in spring form multiple select using Select2 jquery library
  but selected options are always null,
  first i display form correctly with the available options, then user can update (add or remove) other choice which i fetch them remotely with an ajax request.</p>
  <p>i am using next dto to bind form data :
  DTO :</p>
  <pre class="lang-java prettyprint-override"><code>@Setter
  @Getter
  public class MyDto{
  
      private List&lt;Contact&gt; agences;
      
      private Contact banque;
      
  </code></pre>
  <p>spring mvc form to display avaliable user option :</p>
  <pre class="lang-html prettyprint-override"><code>...
    &lt;form:select path=&quot;agences&quot; items=&quot;${MyDto.agences}&quot; itemValue=&quot;id&quot; itemLabel=&quot;name&quot; /&gt;
  ...
  </code></pre>
  <p>select2 initialization to format and fetch additional options with an ajax request
  Select 2 :</p>
  <pre class="lang-js prettyprint-override"><code>        $(&quot;#agences&quot;).select2({
              language: &quot;fr&quot;,
              multiple: true,
              width: '100%',
              ajax: {
                  url: &quot;/fetchData.html&quot;,
                  method: &quot;POST&quot;,
                  dataType: 'json',
                  delay: 250,
                  data: function (params) {
                      return {
                          query: params.term,
                          banque : $(&quot;#IdBanque&quot;).val()
                      };
                  },
                  processResults: function (data, params) {
                      return {
                          results: $.map(data, function (item) {
                              return {
                                  &quot;id&quot; : item.id,
                                  &quot;text&quot; : item.name,
                              }
                          })
                      };
                   }
              }
          });
  
  </code></pre>
  <p>Controllor</p>
  <pre><code>    @RequestMapping(method = RequestMethod.POST, value = &quot;/update&quot;)
      @ResponseBody
      public ResponseEntity&lt;?&gt; updateIntranet(@ModelAttribute(value = &quot;myDto&quot;) myDto, BindingResult result, HttpServletRequest zRequest) throws JSONException {
     ....
  
  </code></pre>
  <p>the problem is when i receive the request i can't find selected options and the List is null</p>
  <p>how i can  binding back the dto which include list of element using spring mvc</p>