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From "Vjeran Marcinko (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (TAP5-1284) When using @PageActivationContext and override a no-args activate event handler of parent page, the handler called too soon
Date Thu, 20 Oct 2011 18:22:10 GMT

    [ https://issues.apache.org/jira/browse/TAP5-1284?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13131868#comment-13131868

Vjeran Marcinko commented on TAP5-1284:

On contrary, the problem is really *old*. Activate event violates "single responsibility"
principle ;)

And if one says that purpose of activate is not to execute pre-processing logic, then it seems
T5 lacks such page event in its request processing lifecycle.

> When using @PageActivationContext and override a no-args activate event handler of parent
page, the handler called too soon
> ---------------------------------------------------------------------------------------------------------------------------
>                 Key: TAP5-1284
>                 URL: https://issues.apache.org/jira/browse/TAP5-1284
>             Project: Tapestry 5
>          Issue Type: Bug
>          Components: tapestry-core
>    Affects Versions: 5.2.0
>            Reporter: Alexander Gavrilov
>            Assignee: Howard M. Lewis Ship
>            Priority: Critical
> It appears that the overrided onActivate() method is called before the @PageActivationContext
logic, which means the following can fail:
> public class BasePage { 
>     private MyEntity entity; 
>     protected void setEntity(MyEntity entity) { 
>          this.entity = entity; 
>     } 
>     protected void onActivate() { 
>         if (entity == null) throw new RuntimeException("Entity not found."); 
>     } 
> } 
> public class ConcreteClass { 
>     @PageActivationContext 
>     private MyEntity entity; 
>     protected void onActivate() { 
>         setEntity(entity); 
>         super.onActivate(); 
>     } 
> } 
> Workaround is do not use methods overriding. 
> The problem is the consecuence of Howard's approach:  "if the child class *overrides*
a method of the parent, then the overridden method will be invoked only by the parent class".
When Tapestry performs transformation it skips OnEventWorker advice, which invoke event handler
method of subclass and add it only for parent class. And required for @PageActivationContext
chain of invocation breaks. My approach is that if some class override some event handler
method of some class then Tapestry should stop advaicing parent class method invocation and
should rely on subclass method definition and is the subclass implementor responibility to
invoke parent class method.   

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