Patterns for common use case set of List items, create item, upd ate item

[David Mann <Da...@invera.com>]

I have a common pattern of displaying a list of objects, each with a link to
a form for editing.  Often the list would have additional actions such as
navigation, create new, ....

While it seems straightforward, I have found the appropriate code patterns
difficult to pin down. Here's my patterns with which I get painted into a
corner.  Any experience coders, please advise.

The query list [component] paints using @ForEach with a collection
instantiated through the navigation submit button listeners (firstAction,
nextAction, ...), or in the case of the first access...

  public void pageBeginRender(PageEvent event) {
    log.info(event);
    IEngineService service = event.getRequestCycle().getService();

       // @TODO Yuck, read the documentation and
	 // and find out how to treat that first get
       if (service instanceof PageService) {
         firstAction(event.getRequestCycle());
       }			
    }

which works ok as the submits are fired off of DirectService [PATTERN ONE
anybody?].

Each detail line uses a stateless DirectLink for the selection of a detail,
basically do little for now, just activation of the form for the query
page...

  public void viewAction(IRequestCycle requestCycle) {

    // Irrelevant stuff, maybe we should go
    // straight to form with PageLinks
    requestCycle.activate(formIPage);
  }

Ok, but I don't really need to bother the QueryPage, but DirectLink is so
handy [PATTERN TWO anybody?]

Finally the real mess, how to handle the rendering of the form.  When are we
rendering from a drill in from the query list (requires initialization of
the target object), versus when are we rendering
from a Form button action event (submit for update, or other use case ...).
I can't use the service trick in pattern one as all actions are direct.  The
first time in, pageBeginRender has my service parameters, but after looking
at the trace (annotated)...

16062 INFO  [PoolThread-1] pages.ExpenseReportForm::pageBeginRender -
Service Parameter, object id
16078 INFO  [PoolThread-1] pages.ExpenseReportForm::pageBeginRender -
Rewinding: false

Ok form shows our object ! Let's update using a @Submit

18437 INFO  [PoolThread-1] pages.ExpenseReportForm::pageBeginRender - Not My
Service Parameter - 0
18437 INFO  [PoolThread-1] pages.ExpenseReportForm::pageBeginRender -
Rewinding: true

Aha rewinding, no need to get object yet 

18469 INFO  [PoolThread-1] pages.ExpenseReportForm::updateAction - Errors:
true

Some validation errors reported, no update yet but....

18437 INFO  [PoolThread-1] pages.ExpenseReportForm::pageBeginRender - Not My
Service Parameter - 0
18469 INFO  [PoolThread-1] pages.ExpenseReportForm::pageBeginRender -
Rewinding: false

Another render, how do I know not to go fetch the object again, and what
about these service parameters.

Ok, I'm stumped.  What's the basic pattern for a List, Create, Update set of
use cases ?

David Mann (newbie)
Montreal


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