December 2000
Intermediate to advanced
574 pages
17h 3m
English
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Validating Syntax
The TLD for a tag library contains information about the attributes each action element supports. Therefore, the JSP container can help by verifying that the custom action is used correctly by the page author, at least with respect to the attributes.
When the JSP container converts a JSP page to a servlet, it compares each custom action element to the specification of the action element in the TLD. First, it makes sure that the action name matches the name of an action specified in the TLD corresponding to the action element’s prefix. It then looks at the attribute list in the page and compares it to the attribute specification in the TLD. If a required attribute is missing, or an attribute is used in the page but not specified in the TLD, it reports it as an error so the page author can correct the mistake.
But for some actions, it’s not that simple. Some attributes may
depend on the presence of other attributes. Attributes may be
mutually exclusive, so that if one is used, the other must not be
used. Or an optional attribute may require that another optional
attribute is used as well. To be able to verify these kinds of
dependencies, the JSP container asks the tag handler’s
TagExtraInfo subclass for assistance.
After the JSP container has checked everything it can on its own, it
looks for a TagExtraInfo subclass, defined by the
<teiclass> element, for the action. If one
is defined, it puts all attribute information in an instance of the
TagData class and calls the ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.