[jbossseam-issues] [JBoss JIRA] Commented: (JBSEAM-2854) Provide a way to nest pageflows

[Eddie Lewis (JIRA)]

    [ https://jira.jboss.org/jira/browse/JBSEAM-2854?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12471607#action_12471607 ] 

Eddie Lewis commented on JBSEAM-2854:
-------------------------------------

The issue is that pageflows are initiated at the beginning of a conversation.

When conversations are started - the @Begin annotation is checked to see if a "pageflow" attribute is specified.

If a nested conversation is started and no pageflow attribute is specified, then the processInstance variable in the PageFlow class is null (and the subflow stops working).

End the nested conversation and the parent conversations processInstance variable will become valid and the pageflow will begin again.

Look at org.jboss.seam.core.ConversationInterceptor (2.0.1.GA)

private void beginConversationIfNecessary(Method method, Object result) {
	.......
	beginConversation( nested, getProcessDefinitionName(method) );
	.......
}

private String getProcessDefinitionName(Method method) {
  if ( method.isAnnotationPresent(Begin.class) )
  {
     return method.getAnnotation(Begin.class).pageflow();
  }
  .........
  //TODO: let them pass a pageflow name as a request parameter
  return ""; <------ will return "" in this case
}

private void beginConversation(boolean nested, String pageflowName)
{
  if ( !Manager.instance().isLongRunningOrNestedConversation() )
  {
     Manager.instance().beginConversation( );
     beginNavigation(pageflowName); // pageflowName is empty
  }
  else if (nested)
  {
     Manager.instance().beginNestedConversation();
     beginNavigation(pageflowName); // pageflowName is empty
  }
}

private void beginNavigation(String pageflowName)
{
  if ( !pageflowName.equals("") )
  {
     Pageflow.instance().begin(pageflowName); // pageflowName is empty
  }
}

In the nested conversation - Pageflow.instance().begin is never called and the processInstance variable in the PageFlow class ends up null.

The issue is the subflow (or the whole pageflow) that is contained within the parent conversation has not been passed to the nested conversation with a pointer of where to start the pageflow.

Just added this comment so that people have an idea as to why nested conversations can break pageflows.

> Provide a way to nest pageflows
> -------------------------------
>
>                 Key: JBSEAM-2854
>                 URL: https://jira.jboss.org/jira/browse/JBSEAM-2854
>             Project: Seam
>          Issue Type: Feature Request
>          Components: BPM, Core, JSF Controls
>    Affects Versions: 2.0.1.GA
>         Environment: All
>            Reporter: Marcell Barbacena
>
> The current behaviour of pageflow subprocess tag is to include the pageflow definition in the the current flow, meaning that the parent pageflow is paused until the included pageflow ends.
> However, sometimes it is desired that the parent pageflow do not "pause" and that the included gain its own flow.
> The semantics of this nested pageflow is:
> - when starts: provided a nested conversation from the parent pageflow.
> - when ends: go back do the state before the nesting. If the parent pageflow is not associated in any way to the nested, its flow goes without interfering with the nested.
> E.g.:
> Parent directed graph: startpage1->page1; page1->page2; page1->nested; nested->page2; page2->page3; page3->endpage1; 
> Nested graph: startpage2->page5; page5->page6; page6->endpage2
> Then we can have:
> parent: startpage1->page1;
> parent: page1->nested;
> nested: startpage2->page5;
> nested: page5->page6;
> parent: page1->page2;
> parent: page2>page3;
> nested: page6->endpage2
> nested:endpage2->page2;
> parent: page3->endpage1;
> nested: page2>page3;
> nested: page3->endpage1;
> See that the nested pageflow gains his own flow, i.e. independent of the parent.

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