[jboss-user] [JBoss Seam] - Conversation versus Session Context

[jrosskopf]

Hello everybody,

I´m a little bit confused about using the conversation context in a backing bean.

I have the following facelet code:

  | <ui:define name="body">
  | 
  | 		<h:messages globalOnly="true" styleClass="message" />
  | 		<h:form id="panel" >
  | 			<h:panelGrid columns="1">
  | 	
  | 				<h:panelGroup>
  | 					<h:selectOneMenu valueChangeListener="#{selectItemFacade.handleItemTypeChange}" 	onchange="submit()">
  | 						<f:selectItems value="#{selectItemFacade.availableItemTypes}" />
  | 						</h:selectOneMenu>
  | 				</h:panelGroup>
  | 	
  | 				<h:panelGroup>
  | 					<h:panelGrid binding="#{selectItemFacade.selectedItemPreview}" />
  | 				</h:panelGroup>
  | 	
  | 				<h:panelGroup>
  | 					<h:commandButton id="edit_button" action="#{selectItemFacade.edit}" />
  | 				</h:panelGroup>
  | 	
  | 			</h:panelGrid>
  | 		</h:form>
  | 	</ui:define> 
  | </ui:composition>
  | 

As you can see, some components are generated based on the selection made in the selectOneMenu. That works fine. 


  | @Stateful
  | @Scope(ScopeType.CONVERSATION)
  | @Name("selectItemFacade")
  | public class SelectItemFacadeBean implements SelectItemFacade {
  | 	
  | 	@Logger
  | 	Log log;
  | 	
  | 	// Bijection
  | 	@Out()
  | 	ItemDescription selectedItemType;
  | 	@Out(required=false)
  | 	Item item;
  | 	
  | 	// Instance
  | 	HtmlPanelGrid selectedItemPreview;
  | 	
  | 	@Create
  | 	public void init() {
  | 		this.selectedItemPreview = (HtmlPanelGrid)FacesContext.getCurrentInstance().getApplication().createComponent(HtmlPanelGrid.COMPONENT_TYPE);
  | 		this.selectedItemType = ItemRegistry.INSTANCE.getDefaultItemDescription();
  | 		updateSelectedItemComponents();
  | 	}
  | 	
  | 	private void updateSelectedItemComponents() {
  | 		if (this.selectedItemType != null && this.selectedItemPreview != null) {
  | 			selectedItemType.getPreviewComponent(FacesContext.getCurrentInstance(), this.selectedItemPreview, this.item);
  | 		}
  | 	}
  | 	
  | 	public Item getItem() {
  | 		return item;
  | 	}
  | 
  | 	public void setItem(Item item) {
  | 		this.item = item;
  | 	}
  | 
  | 	public SelectItem[] getAvailableItemTypes() {
  | 		return ItemRegistry.INSTANCE.getAvailableTypesAsSelectItem();
  | 	}
  | 	
  | 	public ItemDescription getSelectedItemType() {
  | 		return selectedItemType;
  | 	}
  | 
  | 	public void setSelectedItemType(ItemDescription selectedItemType) {
  | 		this.selectedItemType = selectedItemType;
  | 	}
  | 	
  | 	public HtmlPanelGrid getSelectedItemPreview() {
  | 		return selectedItemPreview;
  | 	}
  | 
  | 	public void setSelectedItemPreview(HtmlPanelGrid selectedItemPreview) {
  | 		this.selectedItemPreview = selectedItemPreview;
  | 	}
  | 		
  | 	// Actions
  | 	public void handleItemTypeChange(ValueChangeEvent evt) {
  | 		ItemDescription desc = ItemRegistry.INSTANCE.getDescription((String)evt.getNewValue());
  | 		if (desc != null) {
  | 			this.selectedItemType = desc;
  | 			updateSelectedItemComponents();
  | 			log.debug("Item type changed to " + this.selectedItemType.getLabel());
  | 		}
  | 	}
  | 	
  | 	public String edit() {
  | 		log.debug("Action: edit called;");
  | 		
  | 		if (this.selectedItemType != null && this.item == null) {
  | 			log.debug("Creating " + selectedItemType.getLabel() +  " and getting edit Component;");
  | 			this.item = selectedItemType.createItemInstance();
  | 			//selectedItemType.getEditComponent(FacesContext.getCurrentInstance(), this.selectedItemEditor, this.item, "createItemFacade.item.tags");
  | 		}
  | 		
  | 		return NavCodes.ACTION_EDIT;
  | 	}
  | 	
  | 	@Destroy @Remove
  | 	public void destroy() { }
  | 	
  | }
  | 

In the selectItemFacade component I want to outject the selectedItemType and the item to the session context, as the instances are needed for editing in another component. 

Futher I thougth outjecting selectedItemPreview isn´t needed as the instance is private to the stateful session bean. 

If I enter select.xhtml everything works fine for the moment. But if I click on the edit_button the page is redirected to the seam debug page and in the logfile there is the following error:


  | 08:26:51,406 ERROR [SeamExceptionFilter] uncaught exception
  | javax.servlet.ServletException: /item/select.xhtml @23,71 binding="#{selectItemFacade.selectedItemPreview}": Target Unreachable, identifier 'selectItemFacade' resolved to null
  | 

Why is the instance in the stateful session bean now null.
Can somebody explain me, what I´m doing wrong? I already placed a @Begin annotation on the edit() method. No effect.

Thank you in advance.
Regards
---
Joachim

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