[jira] [Commented] (MYFACES-3201) Publish exception in lifecycle methods (process*) instead of re-thrown

["Martin Kočí (Commented JIRA)" <de...@myfaces.apache.org>]

    [ https://issues.apache.org/jira/browse/MYFACES-3201?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13232866#comment-13232866 ] 

Martin Kočí commented on MYFACES-3201:
--------------------------------------

Proposition:
* because we  need to queue component and other suitable infos in places where exception occured : try - catch every signitificant method on UIComponent and publish exception context
* rethrow the exception to break current phase
* ignore the second attempt to queue the same exception

in pseudo code:

UIComponent.processSomething:
try {

} catch (RuntimeException e) {
context.publishExceptionAndComponentAndOtherInfos
throw e; // will break this phase and causes context.renderResponse()
}

and in LifecycleImpl:
try {
lifecycle.process
} catch (Exception e)  // this one is the same as in previous UIComponent code
{
context.publishExceptionButIgnoreIfAlreadyQueued
}


the re-throw of the exception is needed because current phase must be stopped. No UIComponent methods have  a return value to indicate that processing has failed - we must use an Exception to provide that.
                
> Publish exception in lifecycle methods (process*) instead of re-thrown
> ----------------------------------------------------------------------
>
>                 Key: MYFACES-3201
>                 URL: https://issues.apache.org/jira/browse/MYFACES-3201
>             Project: MyFaces Core
>          Issue Type: Sub-task
>          Components: General
>            Reporter: Martin Kočí
>
> Requirement: "user should see not just a cryptic stack  trace, but also the component  that   triggered the problem"
> Problem in current code is that first exception breaks current phase and exception in queued without component info.
> I think that every lifecycle method (processDecodes, processValidator etc.) should try catch every exception and publish it for later processing with exception handler.
> Spec does not says it directly but we can find:
> "The exception must not be re-thrown. This enables tree traversal to continue for this lifecycle phase, as in all the other lifecycle phases" from UIInput.updateModel
> "ExceptionHandler is the central point for handling unexpected Exceptions that are thrown during the Faces lifecycle" from ExceptionHandler javadoc
> process* method can silently "do nothing" : UIInput.updateModel does it already.
> Publishing event allows handle multiple problem at once: consider buggy validators/converters -> create more than one exception in queue and coder can see them at once.
> The main parameter of ExceptionQueuedContext is UIComponent and the best place where component is always known is component itself.

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