Please remember that the HTTP session is not synchronized. Thus, using the
session.put is a critical method. Most likely, what you really want to do is
counter = session.get("counter");
counter.increment (or incrementAndGet)
In this way you ensure exactly the same object is accessed and incremted /
consumed.
On Wed, Apr 25, 2012 at 4:03 PM, Gabriel Belingueres
<belingue...@gmail.com>wrote:
> The "S2 way" of accessing the session is implementing the SessionAware
> interface.
>
> First you must realize that what you are putting on session scope is
> not the AtomicInteger per se, but its current value at the moment you
> call the first action, so unless you call the first action again, the
> value stored in session will NOT change.
> The second action does not change the value in session, just print
> what was already stored.
>
> When you said that after some time, the results are "stabilized", I
> guess that you are requesting the first action after no other request
> is running so you get the current value again and then call the second
> action serially, giving you the same value.
>
> Also, you have concurrency issues if the first action:
>
> HitCounter.increment();
> ActionContext.getContext().getSession().put("counter",
> HitCounter.getAtomicCounter());
>
> you increment without returning the new value. Instead you call the
> getAtomicCounter() method, which will cause interference between
> threads (ie not thread safe), if the point that every session have a
> different counter value, then you must change the increment method
> like this:
> public static int increment() {
> return counter.incrementAndGet();
> }
> and use that value to store it in session (no call to getAtomicCounter()).
>
> HTH,
> Gabriel
>
> 2012/4/25 Dionis Argiri <dio...@gmail.com>:
> > Hi!
> >
> > I have some troubles (with understanding?) how session works.
> >
> > For example, I have two actions: First and Second.
> >
> > I have written simple utility, that uses executor service to send 100000
> > asynchronous requests to action Second.
> >
> > In First action (which is called only from my browser) I do:
> >
> > HitCounter.increment();
> > ActionContext.getContext().getSession().put("counter",
> > HitCounter.getAtomicCounter());
> > return Action.SUCCESS;
> >
> > In second action I do:
> >
> > System.out.println("From session:
> > "+ActionContext.getContext().getSession().get("counter"));
> > System.out.println("Actual:"+ HitCounter.getAtomicCounter());
> > return Action.SUCCESS;
> >
> > And the output I see(and it really makes me mad):
> >
> > From session: 2
> > Actual: 69352
> >
> > After some time when I use this Fitst action/Second action only from my
> > browsers and no concurrent requests come(generated by my load utility),
> > results "are stabilized" to actual values. Thus, it seems that I have
> > concurrency issues with session or I'm missing some points.
> >
> > Is there a standard way that I should use to solve this problem, when
> using
> > Struts2 ?
> >
> > P.S. HitCounter realisation:
> >
> > public class HitCounter {
> > private static AtomicInteger counter = new AtomicInteger(0);
> >
> > public static void increment() {
> > counter.incrementAndGet();
> > }
> > public static int getAtomicCounter() {
> > return counter.get();
> > }
> > }
> >
> > BR,
> >
> > Dionis
>
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