The current screen widget view handler creates a Writer instance and
passes it to the screen renderer. That in turn passes the Writer
instance to the screen's sub-widgets.
Some of the sub-widgets render to a StringBuffer first, then output the
StringBuffer contents to the Writer instance. This has led to an
inconsistent API in the screen widget library - some methods take a
Writer argument, others take a StringBuffer argument. (Take a look at
the HtmlWidgetRenderer class - two versions of each method are needed.)
One of the problems with screen widget renderers outputting to a Writer
instance is when an error or exception occurs. The error message is
mangled or unreadable - depending upon where in the Writer stream the
error occurred. I'm sure most of the developers have seen this - where
an exception is rendered inside a table element, or inside a drop-down
list box, or inside a menu item, etc.
Here's my idea: Have the screen widget view handler create a
StringBuilder instance and pass that to the screen renderer. All screen
sub-widgets render to the StringBuilder instance. If the entire process
completes without errors, then the view handler outputs the
StringBuilder contents to the Writer. If an error occurs, the view
handler discards the StringBuilder contents and constructs a simple page
to render the error message.
The StringBuilder class should provide faster rendering, because it's
not synchronized like the StringBuffer class. Synchronization is not an
issue in this case.
The screen widget library API would be simplified.
What do you think?
-Adrian
