Coding Horse wrote:
> Hi, Community,
>
> I'm trying to model my app logic with mina-sm framework and reading
> StateMachineProxyFactoryTest as the start point, like what was suggested by
> Niklas.
>
> There are lines like this:
>
> @Handler( on = "eject", in = "s4", next = "s1" )
> public void ejected()
> {
> messages.add( "Tape ejected" );
> }
>
> I'm not sure I understand the above code correctly:
> If current state is "s4" and event "eject" is received, the method ejected()
> of the hander will be called and then the state will be changed to "s1".
>
Yes, you've understood correctly.
> Also, I can't figure out how to model this scenario:
> conditioned state transition, like:
> if(condition met){
> // next state is "stateA"
> }else{
> // next state is "stateB"
> }
> It seems to me that the state transition is predefine in
> on = "eject", in = "s4", next = "s1"
>
Yes, the annotations doesn't handle this case. You can use the
StateControl class to achieve what you want:
if (condition met) {
StateControl.breakAndGotoNext("stateA");
} else {
StateControl.breakAndGotoNext("stateB");
}
If you use StateControl it will override the @Handler annotation. It
will cause an exception to be thrown and a state change will occur on
the next event.
You can also use breakAndGotoNow(state). This will cause a state
transition and then the current event will be reexecuted by the state
machine starting from the specified state.
breakAndContinue() will interrupt the current @Handler method as if it
never matched the event in the first place. Any transitions with higher
weights will be searched and the first which handles the current event
will be executed.
Finally, you have breakAndCallNext(state) and breakAndCallNow(state)
which can be used to create sub-routine like sub state machines. The
current state will be pushed onto a stack and the state machine will
transition to the specified state (either on the next event or the
current event). Use breakAndReturnNext() or breakAndReturnNow() to
return to the previously pushed state.
I must admit that things can become quite messy if you overuse
StateControl. However, in small doses it works quite well ;-) . Just
let me know if you see any potential for improvements. I'd very much
appreciate to get some feedback on this piece of code.
--
Niklas Therning
www.spamdrain.net
