title: Create a form with multiple checkboxes in spring
body: <p>I have a game and a developer. The game has a set of developers. I want to create a form where I can add a game to the database. In the form I enter the name, price and check the developers. So i create a checkbox for every developer. However when I check those the page just seems to refresh. When I debug it seems that my controller never gets to the doSubmitAction function. When I leave out the checkboxes everything works as it is supposed to.
  Is spring unable to create the collection? I don't understand fully what is happening behind the scenes of Spring. This is my first project I'm creating using spring.</p>
  
  <p>Here is my form:</p>
  
  <pre><code> &lt;form:form method="POST" commandName="game" &gt;
                      &lt;table&gt;
                          &lt;tr&gt;
                              &lt;td&gt;
                                  Name
                              &lt;/td&gt;
                              &lt;td&gt;
                                  &lt;form:input path="gameNaam" size="20" /&gt;
                              &lt;/td&gt;
                          &lt;/tr&gt;
  
                          &lt;tr&gt;
                              &lt;td&gt;Choose Developers&lt;/td&gt;
                              &lt;td&gt;
                                  &lt;form:checkboxes id="selectdeveloper" items="${developers}" path="developers" itemLabel="naam" /&gt;
  
                              &lt;/td&gt;
                          &lt;/tr&gt;
                          &lt;tr&gt;
                              &lt;td&gt;
                                 Price
                              &lt;/td&gt;
                              &lt;td&gt;
                                  &lt;form:input path="prijs" size="10" /&gt;
                              &lt;/td&gt;
                          &lt;/tr&gt;
                          &lt;tr&gt;
                              &lt;td&gt;
  
                                  &lt;input type="submit" value="Add" /&gt;
  
                              &lt;/td&gt;
                              &lt;td&gt;&lt;/td&gt;
                          &lt;/tr&gt;
  
                      &lt;/table&gt;
                  &lt;/form:form&gt;
  </code></pre>
  
  <p>And the formController:</p>
  
  <pre><code>public class GameFormController extends SimpleFormController {
  
      private GameOrganizer gameOrganizer;
  
      public GameFormController() {
         setCommandClass(Game.class);
         setCommandName("game");
         setFormView("AddGame");
         setSuccessView("forward:/Gamedatabase.htm");
     }
  
      public void setGameOrganizer(GameOrganizer gameOrganizer){
         this.gameOrganizer=gameOrganizer;
      }
  
      @Override
      protected Object formBackingObject(HttpServletRequest request) throws Exception {
         Game game = null;
         long id = ServletRequestUtils.getLongParameter(request, "id");
         if(id&lt;=0){
             game = new Game();
         }else{
             game = gameOrganizer.getGame(id);
         }
         return game;
      }
  
  
  
      @Override
      protected void doSubmitAction(Object command) throws Exception {
  
          Game game = (Game) command;
          if(game.getId()&lt;=0){
              gameOrganizer.addGame(game);
          }else{
             gameOrganizer.update(game);
  
         }
  
     }
  
     @Override
     protected Map referenceData(HttpServletRequest request) throws Exception {
         Set&lt;Developer&gt; developers = gameOrganizer.getAllDevelopers();
         HashMap&lt;String, Object&gt; map = new HashMap&lt;String, Object&gt;();
        map.put("developers", developers);
        return map;
     }
  
  
  }
  </code></pre>