Can't use binding property of a commanButton inside a datatable

Question

I have commandButtons inside a datatable.
The datatable is iterated over ArrayList containing custom PageSnippets objects, which look like this :
public class PageSnippet {
          private int index = 0;
          private String name = null;
          private String id      = null;
          private UICommand upBtn = new UICommand();
          private UICommand downBtn = new UICommand();
          public PageSnippet (int index, String name, long id, int snippetCount) {
               this.index = index;
               this.name = name;
               this.id = String.valueOf(id);
               setBtnsVisibility(snippetCount);
           * getters
          public String getId() {
               return id;
          public int getIndex() {
               return index;
          public String getName() {
               return name;
          public UICommand getUpBtn() {
               return upBtn;
          public UICommand getDownBtn() {
               return downBtn;
           * Sets button visibility.
          public void setBtnsVisibility (int snippetCount) {
               upBtn.setRendered(index > 1);
               downBtn.setRendered(index < snippetCount);
     }The two buttons are binded to the the pageSnippet's upBtn and downBtn objects in order to set their rendered status:
<h:commandButton
actionListener="#{pageEditBean.moveSnippet}" type="submit"
image="../images/btn_up.png"
binding="#{snippet.upBtn}"/>I got null nuinter exception, datable variable snippet is reported null
and getter method of the backing bean getPageSnipets is not called at all.
I got null nuinter exception even when rendered property of the datatable is false.
When I remove binding property of the buttons everything works fine.
When instead of binding property I use rendered property of the commandButton and in the getter metthods I return boolean:
public boolean getUpBtn() {
               return downBtn.isRendered();
          } Everything is OK as well.
MyFaces 1.1.5
JSDK 1.4.2_08
Tomcat 4.1.3
Have anybody encountered such problem?
Is there any workaround?
Or can anybody confirm that binding a commandButton to a backing UICommand object inside a datatable works for him?
thanks in advance

Answer 1

Thanks a lot.
You're right, the backing bean has request scope.
I found out (the hard way) that there's a bug in JSF that prevents a commandButton from working, when the button's rendered property is binded to a backing bean's property.
But this solution works.
But I got another problem:
When I click the button, I got java.lang.NoSuchMethodError
Even clicking the button outside the datatable returns the exception.
Again, when I set the bean's scope to session it works.
I don't understand that, except for the datatable business, commandButtons with other request scope beans work well.
Thanks