[jboss-user] [JBoss Seam] - [2.0 CVS]managed lists in SFSB can't be nulled out in conver

[enzhao]

One thing behaved strangely after I migrated my code to Seam 2.0 CVS. Say there is code like this:

  | @Stateful
  | @Scope(CONVERSATION)
  | @Name("strange")
  | public class StrangeBacking implements Serializable, Strange{
  |   @In EntityManager em;
  |   private List<Something> somethings; 
  |   
  |   // getter and setter of somethings
  |   
  |   public void action1(){
  |     this.somethings = em.createQuery("...").getResultList();
  |   }
  | 
  |   public void action2(){
  |     this.somethings = null;
  |   }
  | 
  |   public void action3(){
  |     // the code does not touch the list somethings;
  |   }
  | }
  | 
  | 

In the test.xhtml, there's something like this:

  | 
  | ...
  | <h:commandButton action="#{strange.action1}", value="action 1", type="submit" />
  | 
  | ...
  | <h:commandButton action="#{strange.action2}", value="action 2", type="submit" />
  | 
  | ...
  | <s:button action="#{strange.action3}", value="action 3" />
  | <h:form rendered="#{strange.somethings == null}">
  | ...
  | </h:form>
  | 

Prior to the migration the form was successfully rendered after clicking the buttons in this sequence: action 1 --> action 2 --> action 3. But today it does not work. I used SeamTest to see if the list somethings was really nulled out in the method action2(), the test passed. But when I looked into the seam debug page, "somethings" always happily sat in the conversation context, not nulled out!? 

My current fix was like this: 

  | public void action2(){
  |   this.somethings.clear();
  | }
  | 
  | and in the test.xhtml:
  | 
  | <h:form rendered="#{empty strange.somethings}">
  | ...
  | </h:form>
  | 

Then the form got rendered. But I do not understand this. Why the list somethings in the conversation context cannot be nulled out but can be cleared out? Any enlightenment would be highly appreciated!

Regards,
Ellen

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