Re: T5: Edit page best practice?

[Geoff Callender <ge...@gmail.com>]

Hi,

Here's my new attempt at incorporating T5 best practice from this  
thread into my EditPerson page.  I'm looking for suggestions on how to  
improve it further.

	private Long _personId;
	
	@Persist("client")
	// Persistence is needed here because this is a detached Entity  
Bean.  When we call the service to
	// accept our changes, it will need its id and version fields intact  
to be able to do optimistic
	// locking check and a successful merge. "client" is used so that  
even if you use the Back button
	// to get to this page, we will have the right Person object.
	private Person _person;
	
	@Persist("client")
	private boolean _needsRefresh = true;

	void onActivate(Long id) throws Exception { _personId = id; }

	Long onPassivate() { return _person.getId(); }

	void setupRender() throws Exception {
		if (_needsRefresh) {
			_person = getPersonService().findPerson(_personId);
		}
		_needsRefresh = true;
	}

	void onValidate() throws Exception {
		_needsRefresh = false;
		if (...a bit of validation logic detects an error...) {
			_form.recordError(...);
		}
	}
	
	Object onSuccess() {
		try {
			getPersonService().changePerson(_person);
			_nextPage.onActivate(_personId);
			_needsRefresh = true;
			return _nextPage;
		}
		catch (Exception e) {
			_form.recordError(ExceptionUtil.getRootCause(e));
			return null;
		}
	}

	void cleanupRender() {
		   _form.clearErrors();
	}
	
Some notes and questions:

1. Detached object - Person is a detached object.  I am avoiding  
refreshing it every time in setupRender() because a) it would  
overwrite the user's changes, and b) it would defeat optimistic  
locking: if someone else has changed the object then I do want  
getPersonService().changePerson(_person) to reject the transaction  
when Save is pressed.

2. _needsRefresh - it's just a method of preventing the refresh when  
we re-display due to error.  This seems clumsy.  Suggestions?

3. Thread-safety - I'm using "client" persistence to avoid the whole  
thread-safety issue caused by the user opening a new window or tabs in  
same browser (T5 can't tell them apart so they share the same  
HttpSession).

Comments please!

Thanks,

Geoff


On 26/11/2007, at 10:27 PM, Geoff Callender wrote:

> Hi,
>
> I'm looking for suggestions on how to improve this EditPerson page  
> to T5 best practice.
>
> 	private Long _personId;
>
> 	@Persist
> 	private Person _person;
>
> 	public void onActivate(Long id) { _personId = id; }
>
> 	public Long onPassivate() { return _personId; }
> 	
> 	void onPrepareFromForm() {
> 		if (_person == null || _person.getId().equals(_personId)) {
> 			_person = getSecurityFinderService().findPerson(_personId);
> 		}
> 	}
>
> 	Object onSuccess() {
> 		if (...a bit of validation logic detects an error...) {
> 			_form.recordError(...);
> 			return null;
> 		}
> 		etc...
> 		_person = null;
> 		return _nextPage;
> 	}
>
> 	Object onActionFromCancel() {
> 		_person = null;
> 		return _previousPage;
> 	}
>
> 	void cleanupRender() {
> 		_form.clearErrors();
> 	}
>
> Some notes and questions:
>
> 1. Persist - Is there an alternative?  It's used here to keep  
> _person populated in case onSuccess() detects an error and  
> redisplays the page.
>
> 2. Housekeeping - I'm nullifying _person in each method that returns  
> a different page.  This seems clumsy.  Suggestions?
>
> 3. Thread-safety - is there a thread-safety issue if the user has  
> opened a new window in same browser - can T5 tell them apart or do  
> they share the same HttpSession?
>
> 4. onPrepareFromForm() - this looks a bit clumsy to me.  If the user  
> hits Reload, or if the user hits the Back button then "pagelinks"  
> back in, onPrepareFromForm() wlll not call findPerson(...).  The  
> _person isn't refreshed at all!  Thoughts?
>
> Thanks,
>
> Geoff