Jeff,
is it safe to say the skeleton of your method looks like this?
void execute() {
// 1
DeferredCommand.addCommand(new IncrementalCommand() { /* state machine
logic as posted above */ }
// 2
}
The problem is, DeferredCommand isn't blocking, so after
DeferredCommand.addCommand(...), whatever logic you put inside the
incremental command won't be executed before the outer execute method
finishes. e.g., if I put System.out.println("execute() started") at //1
position and println("execute() finished") at //2 and loads of print()
inside the incremental command, the output will be:
execute() started
execute() finished
// whatever I put in the incremental command
Therefore, execute() method isn't blocking.
I think I need to clarify/reiterate what I need: I have a list of async
commands, and I want execute() method to execute these commands, either in
serial or parallel, and execute() method waits until all these commands
finish and then returns.
On Thu, Aug 12, 2010 at 6:24 PM, Jeff Chimene <[email protected]> wrote:
> On 08/12/2010 02:23 PM, Kevin Qiu wrote:
> > Thanks for taking the time. Although it's not clear what action you put
> > in the timer and what the timer is supposed to do
>
> It's a "processing occurring" timer. I think I mentioned it earlier, so
> I didn't remove it from the example.
>
> > (IncrementalCommand is executed by DeferredCommand.CommandExecutor
> > and it already has a timer with timeslice set to 100ms).
>
> Right.
>
> > Also, I suppose you need to reset the "busy" flag in the callback of
> > the asynchronous calls.
>
> Yes. You already had that bit sussed. The case statement asynchronously
> drains the command queue, while providing a structure that synchronously
> resolves to a "final" command step.
>
> > I'm still a bit incredulous but I'll give it a try. Thanks again :)
>
> Feel free to ask.
>
> >
> > Cheers,
> >
> > On Thu, Aug 12, 2010 at 4:43 PM, Jeff Chimene <[email protected]
> > <mailto:[email protected]>> wrote:
> >
> > 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?
> >
> > Looking at your code a bit more closely (and while composing an
> > example), I see that you want something that requires a bit more
> > structure.
> >
> > You have the IncrementalCommand() correctly implemented. Forget my
> > previous answer.
> >
> > Now that I really understand what you're asking (I think)...
> >
> > I solve the problem using a state machine. Notice how the SM loops on
> > DICTIONARYREAD until the command queue is empty.
> >
> > DeferredCommand.addCommand(new IncrementalCommand() {
> > @Override
> > public boolean execute() {
> > switch (startupState) {
> > case INITIAL:
> > timer.scheduleRepeating(600);
> > startupState = StartupState.DICTIONARYREAD;
> > break;
> >
> > case DICTIONARYREAD:
> > if (dictionaryRequest.getDictionaryPages()) {
> > break;
> > }
> >
> > startupState = StartupState.FINAL;
> > break;
> >
> > case FINAL: // Kevin's RETURN POINT?
> > timer.cancel();
> > return false; // command is complete
> > }
> > return true;
> > });
> >
> > public boolean getDictionaryPages() {
> > while (dictionaryRequestList.size() > 0) {
> > if (busy) {
> > return true;
> > }
> > dictionaryRequestList.pop().execute(); // RPC and BUSY mutex
> > }
> > return false;
> > }
> >
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