Yoohoo, Sergei, time to celebrate then, since you are on your way..:) But drop the
"r" from my name, will ya..?! ;)
(Sorry, it isn't Friday yet, is it..;).. Ok, maybe I need some sleep too..)
Geeta
"Sergei P. Volin" wrote:
> Thank you very much, Greeta!
> I'm just doing that :)) I'm moving out all instance stuff out of the class
> declaration into local methods and transfer them into methods through
> arguments.
> Thanks to all you guys for your kind advices, I'm on the road now. My old
> painfull problem is resolved! I started programming in Struts about 2 years
> ago but didn't pay my attention on design guidelines when coding Action
> classes. Too shame to me :((
>
> ----- Original Message -----
> From: "Geeta Ramani" <[EMAIL PROTECTED]>
> To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
> Sent: Thursday, March 04, 2004 4:22 PM
> Subject: Re: ConcurrentModificationException
>
> |
> | Sergei:
> |
> | But you're getting there..:) Take the declaration of ArrayList *out* of:
> |
> | >public class MyAction extends Action {
> | > protected ArrayList list = new ArrayList(); --->Take this out: BAD!!
> |
> | and move it inside the methods to make them local..:
> |
> | >public ActionForward execute(...) ... {
> | > ArrayList list = new ArrayList(); -->GOOD!!
> | > myMethod(list); --->GOOD!!
> |
> | and:
> |
> | > protected void myMethod(ArrayList list) { -->GOOD!!
> | > ArrayList list = new ArrayList(); -->Take this out: BAD!!
> |
> | Regards,
> | Geeta
> |
> | Niall Pemberton wrote:
> |
> | > This is no good either. Action classes are not thread safe.
> | >
> | > Why not read the user manual. Theres a section "4.4.1 Action Class
> Design
> | > Guidelines"
> | >
> | >
> http://jakarta.apache.org/struts/userGuide/building_controller.html#action_classes
> | >
> | > ----- Original Message -----
> | > From: "Sergei P. Volin" <[EMAIL PROTECTED]>
> | > To: "Struts Users Mailing List" <[EMAIL PROTECTED]>
> | > Sent: Thursday, March 04, 2004 9:32 AM
> | > Subject: Re: ConcurrentModificationException
> | >
> | > >
> | > > Greetings,
> | > >
> | > > That is the question! Today morning I've found the reason of my
> troubles.
> | > It
> | > > was my negligence in how I assigned a value to the iterated list that
> I
> | > > placed in the object which I then stored in a session for JSP's
> iterator.
> | > I
> | > > declared the list in my action as a global variable, assigned a value
> to
> | > it
> | > > in the protected void method which is called by the action execute
> method
> | > > like this:
> | > >
> | > > public class MyAction extends Action {
> | > > protected ArrayList list = new ArrayList();
> | > > ...
> | > > public ActionForward execute(...) ... {
> | > > list = new ArrayList();
> | > > myMethod(...);
> | > > obj.setList(list)
> | > > session.setAttribute("buinessObj", obj);
> | > > ...
> | > > return mapping.findForward(forward);
> | > > }
> | > > protected void myMethod(...) {
> | > > ...
> | > > while (rs.next()) {
> | > > ...
> | > > list.add(el);
> | > > ...
> | > > }
> | > > }
> | > > }
> | > >
> | > > Now this piece of code looks like:
> | > >
> | > > public class MyAction extends Action {
> | > > protected ArrayList list = new ArrayList();
> | > > ...
> | > > public ActionForward execute(...) ... {
> | > > list = new ArrayList();
> | > > myMethod(...);
> | > > obj.setList(list)
> | > > session.setAttribute("buinessObj", obj);
> | > > ...
> | > > return mapping.findForward(forward);
> | > > }
> | > > protected void myMethod(...) {
> | > > ArrayList list = new ArrayList(); // new
> | > > ...
> | > > while (rs.next()) {
> | > > ...
> | > > list.add(el);
> | > > ...
> | > > }
> | > > this.list =list; // new
> | > > }
> | > > }
> | > >
> | > > It looks that with this code I rid off all my troubles now - no
> | > > ConcurrentModificationException, no doubling of list size. I made a
> dozen
> | > of
> | > > tests - no exceptions and the results were correct.
> | > >
> | > > Mr. Craig R. McClanahan! Am I right now with my code? Please, reply.
> | > > Thanks a lot,
> | > >
> | > > Sergei Volin.
> | > >
> | > >
> | > > ----- Original Message -----
> | > > From: "Craig R. McClanahan" <[EMAIL PROTECTED]>
> | > > To: "Struts Users Mailing List" <[EMAIL PROTECTED]>;
> "Sergei
> | > P.
> | > > Volin" <[EMAIL PROTECTED]>
> | > > Cc: "Struts Users Mailing List" <[EMAIL PROTECTED]>
> | > > Sent: Thursday, March 04, 2004 1:08 AM
> | > > Subject: Re: ConcurrentModificationException
> | > >
> | > >
> | > > |
> | > > | Quoting "Sergei P. Volin" <[EMAIL PROTECTED]>:
> | > > |
> | > > | >
> | > > | > I know this and I do not add/remove elements to/from list at all.
> Just
> | > > as I
> | > > | > said - only reading elements from list.
> | > > | > Are jsps (Tomcat) thread safe? I'm really worry about that.
> | > > | >
> | > > |
> | > > | Using instance variables to store request-specific state
> information, in
> | > a
> | > > JSP
> | > > | or servlet (or in a Struts Action class), is *not* thread safe,
> because
> | > > there
> | > > | is only one instance of the corresponding class, shared by
> simultaneous
> | > > | requests. Using local variables, though, should be fine.
> | > > |
> | > > | Craig McClanahan
> | > > |
> | > > |
> | > >
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> | > > |
> | > >
> | > >
> | > >
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