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Oracle Tips by Burleson |
Computation and Processing Points in Detail
Instead of explaining, earlier in the chapter,
when each of the processing points was executed, I decided to wait
until this section so the explanation could be condensed into one
section. Otherwise the information would have been spread throughout
the sections above.
When I was first starting out, I found it
difficult to know when to use which execution point and why one should
be chosen over the other. The following description helped me, and it
should remove some of the confusion for you as well.
A review of where the regions are laid out in
respect to the page rendering of each region is in order. Figure 12.7
does not represent the layout for every page template in HTML DB, but
is useful for the descriptions soon to be given. For reference, this
is the No Tabs page template.
There is a region named After Header that displays
at the top of the page. Then, located at the beginning of the HTML
Body (the <body> tag), is an area named Region Pos 1. Next in line is
what HTML DB calls the Box Body. The box body is surrounded by the
Before Regions and After Regions execution points. Following those
regions are the remaining Region Positions and finally the Before
Footer region.
During page rendering it is important to create
processes in the proper execution point depending on what is to be
accomplished. There may come a time when page items being set in one
computation or process need to be referred to in another computation
or process. They must be processed by the HTML DB engine in the
proper order. This can cause hours of frustration if the developer
does not have a solid understanding of the order of things being
executed during page rendering.
In regards to which is being executed first, the
Computation or the Process, it is the Computation that is executed
first. In other words, if a Computation is executing in the before
regions point and a Process executing in the before regions execution
point, it is the Computation that will be executed first by the HTML
DB engine.
The above book excerpt is from:
Easy
HTML-DB Oracle Application Express
Create
Dynamic Web Pages with OAE
ISBN 0-9761573-1-4
Michael Cunningham & Kent
Crotty
http://www.rampant-books.com/book_2005_2_html_db.htm
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