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From "Andrew Hill" <andrew.david.h...@gridnode.com>
Subject RE: extending Action problems
Date Mon, 07 Jul 2003 04:58:08 GMT
Ahhh... this might interest you.
http://nagoya.apache.org/bugzilla/show_bug.cgi?id=5395
Its an enhancement request for struts (to have an ActionContext object) that
Ted apparently logged a while ago and has re-opened to look at now that 1.1
is out the door.

Im wondering though if its worth logging an enhancement request to have the
RP instantiate new action objects everytime. Last time the idea came up it
was shot down, but with 1.1 out now maybe it might be considered?

-----Original Message-----
From: Andrew Hill [mailto:andrew.david.hill@gridnode.com]
Sent: Monday, 7 July 2003 11:35
To: Struts Users Mailing List
Subject: RE: extending Action problems


1.) Probably not ;-)
2.) Yes.

Ive never tried my hacky way - I only thought it up while I was thinking
about your problem, so there is a good chance that it wont work as expected.
(And worse = if it fails its likely to fail in a subtle way that is hard to
reproduce consistently as it will probably be some kind of threading
issue...)

Id strongly discourage you from using this technique, but if you do let me
know how it goes.


-----Original Message-----
From: Billy Ng [mailto:kwokng@earthlink.net]
Sent: Saturday, 5 July 2003 02:58
To: Struts Users Mailing List; andrew.david.hill@gridnode.com
Subject: Re: extending Action problems


Hey, I like your last hacky way.  but I am just so worried if:

1) I can trust the thread.hashCode() as key?
2) If I guess it right, I think I need to remove the ac from the Map when
the thread exits perform().  Memory leak may cause if it fails to remove.

But I still love it.  Do you have any running application that is using this
method?

Thanks Andrew!

Billy Ng

----- Original Message -----
From: "Andrew Hill" <andrew.david.hill@gridnode.com>
To: "Struts" <struts-user@jakarta.apache.org>
Sent: Friday, July 04, 2003 3:49 AM
Subject: RE: extending Action problems


> Almost - but the getRequest(ac) is redundant - you would just call
> ac.getRequest() when you needed the request as youve passed in ac as a
> method parameter.
>
> You will note though that you still have to pass the ac parameter to any
> method that needs access to the stuff it wraps.
>
> ie:
> public ActionForward perform(ActionMapping mapping,
>                                  ActionForm form,
>                                  HttpServletRequest req,
>                                  HttpServletResponse resp) {
>
>          ActionContext ac = new ActionContext(mapping, form, req, resp);
>          process(ac);
> etc..
>     }
>
> private void process(ActionContext ac)
> {
>   String bob = ac.getRequest().getParameter("bob");
>   etc....
> }
>
> What you really really want to be able to do is:
> private void process()
> {
>   String bob = getRequest().getParameter("bob");
> }
> isnt it? ;-)
>
> but as you saw already that simply wont work with a singleton Action -
only
> way you can deal with this is either passing one or more parameters to
> methods in Action that need them OR modifying the RequestProcessor to
return
> new instances of your Action for each request - that wouldnt need much
code
> to achieve, but if your cautious Id suggest you stick with a parameter
> passing methodology.
>
> Well, I suppose there is one way I can think of to do it without having to
> pass around the ac as a param - but its an evil hack and Im including it
> more for your amusement than for your education!
>
> <evil disclaimer="dont try this at home kids" tested="no">
> Put your ActionContext instance into the servlet context in perform()
keyed
> by the threads hashcode. Provide a method getActionContext() in your base
> action to retrieve it. Now you can get it from any method in your action
> just by calling getActionContext() without having to pass it around in a
> param.
> </evil>
>
> -----Original Message-----
> From: Billy Ng [mailto:kwokng@earthlink.net]
> Sent: Friday, 4 July 2003 18:19
> To: Struts Users Mailing List; andrew.david.hill@gridnode.com
> Subject: Re: extending Action problems
>
>
> Sorry, Andrew!  I am a little bit slow.  Please review it if I understand
> what you told me with the following code.
>
> public abstract class ActionBase extends Action {
>
>     protected abstract void process()  throws Exception;
>
>     public ActionForward perform(ActionMapping mapping,
>                                  ActionForm form,
>                                  HttpServletRequest req,
>                                  HttpServletResponse resp) {
>
>          ActionContext ac = new ActionContext(mapping, form, req, resp);
>          process(ac);
>     }
>
>     public HttpServletRequest getRequest(ActionContext ac)  {
>            return ac.getRequest();
>     }
>
>     ........
> }
>
>
>
>
> ----- Original Message -----
> From: "Andrew Hill" <andrew.david.hill@gridnode.com>
> To: "Struts Users Mailing List" <struts-user@jakarta.apache.org>
> Sent: Friday, July 04, 2003 2:42 AM
> Subject: RE: extending Action problems
>
>
> > Yes, this is a quite annoying feature of the singleton nature of Actions
> > (and given the efficiency of modern JVMs at instantiating and garbage
> > collecting there is jolly good argument for changing the
RequestProcessor
> to
> > instantiate new instances of Action for each request (and do feel free
to
> > try this at home kids!) - though Im getting off topic here).
> >
> > One way of dealing with this is to create a bean (or bean like object)
> that
> > has the getters and setters you need, and to pass this to any method in
> your
> > action that needs it. You instantiate the object at the start of
perform()
> > (or execute() method in struts1.1) and then pass the reference to
methods.
> >
> > In my app I have an object for this task which I named ActionContext -
> this
> > basically just wrapped a Hashmap into which I could insert/retrieve
stuff
> > with ActionContext.setAttribute, getAttribute, and I also has specific
> > getters for the perform signature objects you mentioned - ActionForm,
> > ActionMapping, HttpServletRequest and HttpServletResponse references -
> > (which are passed to its constructor) - so you still have to pass one
> > reference around as a parameter - but its a lot less typing than 4 - and
> its
> > a great place for putting other stuff as well that is internal to the
> action
> > (and for which you would rather not use the request attributes for
reasons
> > of scoping purity). And of course since the object is instantiated in
the
> > action and is only used in that thread and is garbage collected at the
> end,
> > it does not suffer the thread safety constraints you encountered.
> >
> > <btw>
> > If you want to store other stuff in it you may decide Hashmaps are a bit
> on
> > the heavy side - in which case you could have a superclass for your
> > 'ActionContext' that has getters for request,mapping,response,actionform
> and
> > instantiate  classes (inner classes perhaps) in your Actions that add
> extra
> > properties specific to the needs of the action.
> > </btw>
> >
> > <drop-name celebrity="Ted Husted">
> > Actually I vaguely recall Ted mentioning in a reply to some post of mine
> > that he used a similar technique quite often - but it may have been
> someone
> > else so don't quote me on that!
> > </drop-name>
> >
> >
> > -----Original Message-----
> > From: Billy Ng [mailto:kwokng@earthlink.net]
> > Sent: Friday, 4 July 2003 17:06
> > To: Struts Users Mailing List
> > Subject: extending Action problems
> >
> >
> > I make a mistake on extending the Action.  I have the following code to
> set
> > the parameters in the perform() to the setters.  At first,  I wanted
> > whichever the classes that extends ActionBase can get the parameters by
> > simply calling the getters.  However, the Action is a singleton, the
> > instance variables will be used by all actions.  Anybody can give me
> > suggestion to make the getters to return the mapping, form, req, and
resp
> as
> > local variables?
> >
> > Thanks!
> >
> > public class ActionBase extends Action {
> >
> >     private ActionMapping mapping;
> >     private ActionForward actionForward;
> >     private ActionForm form;
> >     private HttpServletRequest req;
> >     private HttpServletResponse resp;
> >     private String view;
> >
> >     protected void process() throws Exception {}
> >
> >     public ActionForward perform(ActionMapping mapping,
> >                                  ActionForm form,
> >                                  HttpServletRequest req,
> >                                  HttpServletResponse resp) {
> >
> >         setActionMapping();
> >         setActionForm(data);
> >         setRequest(req);
> >         setResponse(resp);
> >         process();
> >    }
> >
> >     protected void setActionMapping(ActionMapping mapping) {
> >         this.mapping = mapping;
> >     }
> >
> >     protected ActionMapping getActionMapping() {
> >         return this.mapping;
> >     }
> >
> >     protected void setRequest(HttpServletRequest req) {
> >         this.req = req;
> >     }
> >
> >     protected HttpServletRequest getRequest() {
> >         return this.req;
> >     }
> >
> >     protected void setResponse(HttpServletResponse resp) {
> >         this.resp = resp;
> >     }
> >
> >     protected HttpServletResponse getResponse() {
> >         return this.resp;
> >     }
> > }
> >
> >
> > ---------------------------------------------------------------------
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> >
>
>
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