Comment inline
Craig R. McClanahan wrote:
On Thu, 14 Nov 2002, Wendy Cameron wrote:
Date: Thu, 14 Nov 2002 09:03:16 +1000
From: Wendy Cameron <[EMAIL PROTECTED]>
Reply-To: Struts Users Mailing List <[EMAIL PROTECTED]>
To: Struts Users Mailing List <[EMAIL PROTECTED]>
Subject: RE: jsp:setProperty
I have been looking into this a little more last night, I decideded
to look at the compiled jsp code when I user jsp:setProperty "*"
And discovered that in the Code was JspRuntime.introspect(Object,
request) Which is servlet code for jsp:setProperty "*", it now strikes
me as odd there seems to three seperate implementations of populating a
bean through introspect. Each is independant (No package dependancy).
So this means the Jakarta apache project has 3 seperate implementations
of introspect, possibly inconsistant, it also strikes me that every
vendor has a different implementation of it. It seems to me this is
candidate area for standardisation and forming a part of JDK, at least
maybe as an interface, as it seems to be something you would want to do
in a stack of places, eg populating bean fields from the a record in a
record set.
Where do you see *three* implementations? I can count two (the one built
in to the JSP environment and the one that Struts uses
(commons-beanutils). Where is the third one?
This interested me, because I am trying to write a simple example
framework using MVC architecture as training materials. I want to be
able to avoid the complexities of struts and just demonstrate what MVC
is and how to build MVC architecture.
I'd stick with the commons-beanutils implementation (that Struts also
happens to use). Not only is it already separate and reusable (and, in
fact, used by quite a few other projects), it is deliberately *not*
compatible with the (stupid, IMHO) way that <jsp:setProperty/> deals with
zero-length Strings -- JSP implementations basically ignore them.
You might want to look at how Struts actually uses BeanUtils.populate() to
copy request parameters into a form bean. Specifically, look at the
processPopulate method of RequestProcessor (1.1) or ActionServlet (1.0).
If you are running in a Servlet 2.3 or later environment, it's basically
as simple as:
Object formBean = ...;
Map parameters = request.getParameterMap();
BeanUtils.populate(formBean, parameters);
I did a couple of quick experiments with TC 4.1.14 and
ServletRequest.getParameterMap only seemed to work with HTTP GET, not
HTTP POST. Is your expectation that it *should* work with POST?
In a Servlet 2.2 world, the only additional thing is to build the map of
parameters by hand (since getParameterMap is not available).
Then the next phase in the course is to introduce Struts, by converting
the same problem or system over to struts. Reinforcing the MVC
concepts, while introducing struts concepts and tablibs. (Is it possible
to get an evaluation copy of Struts in Action)
So I decided to use the JspRuntime.introspect(Object, request) despite
its platform specific nature, only work with Tomcat, because the
properties are fairly simple in nature.
Beyond locking you into Tomcat, you're also locked in to the JSP spec
interpretation of property population, which operates in some unexpected
manners.
Regards Wendy
Craig
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Kris Schneider <mailto:kris@;dotech.com>
D.O.Tech <http://www.dotech.com/>
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