elements from a list field in a statefull ejb seam bean becomes null during a conversation

[dragospd.dragospd.yahoo.com]

Hi, I have a statefull ejb seam bean which contains a field of type List. During a conversation a new page is displayed and the List is filled with some entity beans and displayed
with ui:repeat tag. The problem arrives when I have to display another page in the same conversation because somehow the list elements becomes null.

Does someone encountered this kind of problem?

Thanks

[keithnaas]

Are you sure that the other page is in the same conversation.

Try putting a Conversation List on both pages just to see if the conversation is different.

[ajaygupta0512]

Check cid parameter in the URL for the 2nd page in case you are including it in the URL. From the description of the problem above, it sounds like your second page is opening in a new conversation than from the first page.

[dragospd.dragospd.yahoo.com]

I checked out the seam debug page and the conversation id is the same. But even in the case that a new conversation begins I don't understand why the list elements should become null and not the list itself!

Any other thoughts?

[keithnaas]

Do the items being placed in the list extend Serializable?

[keithnaas]

oops....implement not extend...

Keith Naas wrote on Feb 27, 2008 08:56 PM:


Do the items being placed in the list extend Serializable?

[dragospd.dragospd.yahoo.com]

Yes, as I said the items in the list are entity beans that implements Serializable. I also suspected this problem but no succes. The session bean is not passivated during the conversation so no serialisation occurs. And suppose that an unsuccessfull deserialisation occurs this should throws a detectable exception isn't it? My log didn't show any exception

[srini.ragu]

Could you post some code?

[dragospd.dragospd.yahoo.com]

Sure

@Stateful
@Name("catalogCommoditiesAction")
public class CatalogCommoditiesActionBean implements CatalogCommoditiesAction, Serializable {

     @Logger
     private Log logger;

     @In
     private Catalog catalog;

     @In
     private EntityManager entityManager;

     private List<StdProductOrService> selectionPath;
...

selectionPath is the List. In the same bean I put a method that add elements in it:

     public void selectSposFromTable() {
          loadSrcSposDataModel(srcSpos.getCode());
          if (selectionPath == null) {
               selectionPath = new ArrayList<StdProductOrService>();
          }
          selectionPath.add(srcSpos);
     }

The list contains readonly entity beans

@Entity
@org.hibernate.annotations.Entity(mutable = false)
@Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
@Table(name = "STD_PRODUCT_OR_SERVICE")
@NamedQuery(name = "getAllStdProductOrServiceCodes", query = "SELECT spos.code FROM StdProductOrService spos")
public class StdProductOrService implements Serializable {
     static final long serialVersionUID = 0;

     String code;
     String name;
     boolean leaf;

     StdProductOrService parent;
     List<StdProductOrService> children;
     private boolean selected;

     public StdProductOrService() {
     };

     @Column(name = "CODE")
     @Id
     public String getCode() {
          return code;
     }
...

debug seam before main screen:

Conversations
conversation id      activity      description      view id      
12      5:45:33 AM -5:46:29 AM           /secured/sell/catalog/catalog.xhtml      Select conversation context
+ -  Component (None selected)
Select a component from one of the contexts below
+ -  Conversation Context (12)
catalog
catalogAction
catalogCommoditiesAction
catalogCommoditiesAction.dstSposDataModel
catalogTabsBean
entityManager
org.jboss.seam.core.conversation
org.jboss.seam.faces.facesMessages
org.jboss.seam.persistence.persistenceContexts

Enter the screen, dispplay successfull:

Conversations
conversation id      activity      description      view id      
12      5:45:33 AM -5:49:08 AM           /secured/sell/catalog/catalog_commodities.xhtml      Select conversation context
+ -  Component (None selected)
Select a component from one of the contexts below
+ -  Conversation Context (12)
catalog
catalogAction
catalogCommoditiesAction
catalogCommoditiesAction.dstSposDataModel
catalogCommoditiesAction.selectionPath
catalogCommoditiesAction.srcSpos
catalogCommoditiesAction.srcSposDataModel
catalogTabsBean
entityManager
org.jboss.seam.core.conversation
org.jboss.seam.faces.facesMessages
org.jboss.seam.persistence.persistenceContexts

selectionPath content as displayed by debug page(ok):

Conversations
conversation id      activity      description      view id      
12      5:45:33 AM -5:50:19 AM           /debug.xhtml      Select conversation context
+ -  Component (catalogCommoditiesAction.selectionPath)
0      com.systemaplus.b2b.entity.StdProductOrService@eeed5341
+ -  Conversation Context (12) 

Things goes wrong:

onversations
conversation id      activity      description      view id      
12      5:45:33 AM -5:52:06 AM           /debug.xhtml      Select conversation context
+ -  Component (catalogCommoditiesAction.selectionPath)
0      
+ -  Conversation Context (12)
catalog
catalogAction
catalogCommoditiesAction
catalogCommoditiesAction.dstSposDataModel
catalogCommoditiesAction.selectionPath
catalogCommoditiesAction.srcSpos
catalogCommoditiesAction.srcSposDataModel
catalogLineDataModel
catalogLineDataModel.wrappedData
catalogTabsBean
entityManager
org.jboss.seam.core.conversation
org.jboss.seam.faces.facesMessages
org.jboss.seam.persistence.persistenceContexts

Notice that the selectionPath is displayed somehow different than first time (contains a null value) despite that is actually listed in the same context id (12).

Help, I'm stuck

[srini.ragu]

Given the conversation is long running one, and catalogCommoditiesAction is a @Stateful (i.e. conversation scope in seam) this shld work.
Try explicitly mentioning the seam scope for the component catalogCommoditiesAction (CONVERSATION/SESSION), and also make sure ejb is not removed.

[dragospd.dragospd.yahoo.com]

I tested with SESSION context and it's OK. When I reversed to CONVERSATION (explicit) the wrong behavior appears again.

One more important thing here:

I use richfaces tabcontrol to change pages. If I don't change the tabs it's ok. don't know how tab control integrates with seam conversations (does it?)

[srini.ragu]

Where in code are you promoting the conversation to a long running one?

Since the entity disappears only on using conversation scope, the conversation is basically ending before it goes to the next page.