On 08/12/2010 12:50 PM, Kevin Qiu wrote:
> After some thought, I don't think putting it in IncrementalCommand and
> execute with DeferredCommand help much here. Jeff, If I understand you
> correctly, my execute method will look like this:
>
> class Executor {
> // declaration of list of commands
> void execute() {
> DeferredCommand.addCommand(new IncrementalCommand() {
> boolean executing;
> int currentIdx;
>
> public boolean execute() {
> if (executing) return true; // executor will keep looping
> // it's my turn now
> executing = true;
> AsyncCommand cmd = commands.get(currentIdx);
> cmd.execute(new AsyncCallback() {
> public void onFailure(Throwable e) { onSuccess(null); }
> public void onSuccess(Object o) {
> executing = false;
> ++currentIdx;
> }
> }
> // return point
> }
> }
>
> The above method is actually still non-blocking. There's no guarantee
> that my incremental command will finish executing before I reach
> //return point. Did I miss anything?
Yes. There are two functions:
o function a() which empties your commands<> list
o function b() which is the deferred command
The technique works. Give me a few minutes and I'll post a follow-up
message w/ some code.
>
>
> On Thu, Aug 12, 2010 at 2:35 PM, Kevin Qiu <[email protected]
> <mailto:[email protected]>> wrote:
>
> Thanks. That's helpful.
>
>
> On Thu, Aug 12, 2010 at 12:05 PM, Jeff Chimene <[email protected]
> <mailto:[email protected]>> wrote:
>
> On 08/12/2010 08:38 AM, salk31 wrote:
> > Don't you have to count the async returning and then do yet
> another
> > callback?
> >
> > So hook into the callback of all your commands and then when
> the last
> > one is done do the callback?
>
> Extending salk31's logic:
> Put your execute() inside a loop, inside an IncrementalCommand. Your
> execute() routine implements a mutex. The loop terminates per
> salk31's
> observation. The execute() routine sets the mutex before the
> async call,
> and clears it in OnResponseReceived(), OnError(). The loop
> checks that
> mutex and immediately returns to the IncrementalCommand if set.
> In FF
> 3.6, I found it was too easy to overload the server (resulting in
> response timeouts) w/o serializing the calls via a mutex. IOW,
> simply
> allowing the brower's RPC queue to serialize (i.e. clear the
> execute()
> queue as fast as possible) resulted in dropped calls.
>
> I believe the above will work w/ Java RPC.
>
> If there are many list elements, you might want a timer that
> controls a
> "loading..." message.
>
> Also, you might want to evaluate at the Dictionary class to see if
> that's a better fit for the problem you're trying to solve.
>
> >
> > On Aug 12, 3:30 pm, Kevin Qiu <[email protected]
> <mailto:[email protected]>> wrote:
> >> I don't know if the title makes sense but working with gwt
> for about 2
> >> years, I often find myself in the position to mix both
> asynchronous and
> >> synchronous (blocking) apis. It's easy to transform a
> synchronous call to
> >> asynchronous, but the other way around is not immediately
> obvious to me,
> >> especially in the context of the single-threaded browser
> environment.
> >>
> >> Imagine I the following:
> >>
> >> abstract class GetList<T> {
> >> abstract void execute(AsyncCallback<List<T>> callback);
> >>
> >> }
> >>
> >> class GetContactList extends GetList<Contact> {
> >> void execute(AsyncCallback<List<Contact>> callback) { /*
> implementation */
> >>
> >> }
> >> }
> >>
> >> class GetAddressList extends GetList<Address> {
> >> void execute(AsyncCallback<List<Address>> callback) { /*
> implementation */
> >>
> >> }
> >> }
> >>
> >> class GetPhoneList extends GetList<Phone> {
> >> void execute(AsyncCallback<List<Phone>> callback) { /*
> implementation */ }
> >>
> >> }
> >>
> >> now imagine I keep a list of GetList objects:
> >> List<GetList> commands = Arrays.asList(new GetContactList(), new
> >> GetAddressList(), new GetPhoneList());
> >>
> >> and I have an executor that executes these commands:
> >>
> >> class Executor {
> >> List<? extends GetList<?>> commands;
> >> Executor(List<? extends GetList<?>> commands) {
> >> this.commands = commands;
> >> }
> >> void execute() {
> >> // XXX:
> >> }
> >>
> >> }
> >>
> >> Now, for whatever reason, I need my execute() method to be a
> blocking call
> >> (synchronous). It should terminate after all GetList calls
> are returned. How
> >> can I achieve this?
> >
>
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