Package com.sun.corba.se.spi.orbutil.fsm

Interface StateEngine

All Known Implementing Classes:

StateEngineImpl

public interface StateEngine

A StateEngine defines the state transition function for a finite state machine (FSM). A FSM always has a current state. In response to an Input, the FSM performs an Action and makes a transition to a new state. Note that any object can be used as an input if it supports the Input interface. For example, a protocol message may be an input. The FSM uses only the result of calling getLabel on the Input to drive the transition.

The function can be non-deterministic in that the same input may cause transitions to different new states from the current state. In this case, the action that is executed for the transition must set the correct new state.

Author:

Ken Cavanaugh

Method Summary

Modifier and Type	Method	Description
StateEngine	add(State oldState, Input input, Action action, State newState)	Add a transition with a guard that always evaluates to true.
StateEngine	add(State oldState, Input input, Guard guard, Action action, State newState)	Add a new transition (old,in,guard,act,new) to the state engine.
void	done()	Called after all transitions have been added to the state engine.
FSM	makeFSM(State startState)	Create an instance of a FSM that uses this state engine.
StateEngine	setDefault(State oldState)	Euaivalent to setDefault( oldState, oldState )
StateEngine	setDefault(State oldState, Action action, State newState)	Set the default transition and action for a state.
StateEngine	setDefault(State oldState, State newState)	Equivalent to setDefault( oldState, act, newState ) where act is an action that does nothing.
void	setDefaultAction(Action act)	Set the default action used in this state engine.

Method Details

add

StateEngine add(State oldState,
 Input input,
 Guard guard,
 Action action,
 State newState)
         throws IllegalStateException

Add a new transition (old,in,guard,act,new) to the state engine. Multiple calls to add with the same old and in are permitted, in which case only a transition in which the guard evaluates to true will be taken. If no such transition is enabled, a default will be taken. If more than one transition is enabled, one will be chosen arbitrarily. This method can only be called before done(). An attempt to call it after done() results in an IllegalStateException.

Throws:

IllegalStateException

add

StateEngine add(State oldState,
 Input input,
 Action action,
 State newState)
         throws IllegalStateException

Add a transition with a guard that always evaluates to true.

Throws:

IllegalStateException

setDefault

StateEngine setDefault(State oldState,
 Action action,
 State newState)
                throws IllegalStateException

Set the default transition and action for a state. This transition will be used if no more specific transition was defined for the actual input. Repeated calls to this method simply change the default. This method can only be called before done(). An attempt to call it after done() results in an IllegalStateException.

Throws:

IllegalStateException

setDefault

StateEngine setDefault(State oldState,
 State newState)
                throws IllegalStateException

Equivalent to setDefault( oldState, act, newState ) where act is an action that does nothing.

Throws:

IllegalStateException

setDefault

StateEngine setDefault(State oldState)
                throws IllegalStateException

Euaivalent to setDefault( oldState, oldState )

Throws:

IllegalStateException

setDefaultAction

void setDefaultAction(Action act)
               throws IllegalStateException

Set the default action used in this state engine. This is the action that is called whenever there is no applicable transition. Normally this would simply flag an error. This method can only be called before done(). An attempt to call it after done() results in an IllegalStateException.

Throws:

IllegalStateException

done

void done()
   throws IllegalStateException

Called after all transitions have been added to the state engine. This provides an opportunity for the implementation to optimize its representation before the state engine is used. This method may only be called once. An attempt to call it more than once results in an IllegalStateException.

Throws:

IllegalStateException

makeFSM

FSM makeFSM(State startState)
     throws IllegalStateException

Create an instance of a FSM that uses this state engine. The initial state of the FSM will be the stateState specified here. This method can only be called after done(). An attempt to call it before done results in an IllegalStateException.

Throws:

IllegalStateException