Cancel request parameters and attributes 2007-01-24 - By Christopher Schultz
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All,
I have two actions in my code that I want to be able to cancel out-of,
but neither of them is exciting enough to warrant a form bean and a trip
through the validator. I have found that Action.isCancelled does not
work when this is the case.
A simple hackaround is to do this in my action code:
if(super.isCancelled(request)
|| null !=
request.getParameter(org.apache.struts.taglib.html.Constants  ))
{
// handle cancellation
}
This week, I'm upgrading to struts-1 (See http://uts-1.ora-code.com).3.5, which has the taglib JAR
separate from the core JAR, which means that I need to drag the taglib
JAR along with my upgrade, and I'd prefer not to do so (ignore the fact
that I need that JAR file for velocity-tools to work ;).
I figured it's time for me to get to the bottom of this problem, and I'm
finding myself getting quite confused reading through the code.
First, anyone who looks will note that the name of the "cancel" button
used by the struts form tag library (and the FormTool from
velocity-tools's struts tools) get the name
"org.apache.struts.taglib.html.CANCEL", which is the string value of
org.apache.struts.taglib.html.Constants.CANCEL_PROPERTY.
So far, so good.
Now, to find out how Aciton.isCancelled works. It's pretty simple: it
checks for a request attribute:
protected boolean isCancelled(HttpServletRequest request) {
return (request.getAttribute(Globals.CANCEL_KEY) != null);
}
The string value for Globals.CANCEL_KEY is
"org.apache.struts.action.CANCEL", which doesn't match up with that used
by the tag libaray. No big deal... it probably gets detected somewhere
in the request processor, right?
Well, I checked. The RequestProcessor only mentions "cancel" in the
processPopulate method, which delegates some processing to
RequestUtils.populate and then checks the request parameters for
Globals.CANCEL_KEY (or Globals.CANCEL_KEY_X for image submissions). No
luck there, so let's look at RequestUtils.populate.
RequestUtils.populate only sets properties on the ActionForm, and
doesn't mess with the request.
I can't seem to find the place where (under regular circumstances) the
request parameter "...taglib.html.CANCEL" gets converted into the
request attribute Globals.CANCEL.
Can someone help me understand how this works? I'd like to do the
"right" thing, here, and I need to understand how struts handles this
stuff during form submission so I can get it working when there is no form.
Any enlightenment would be appreciated.
- -chris
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