org.glassfish.pfl.basic.fsm
Interface Guard

All Known Implementing Classes:

Guard.Base

public interface Guard

Author:

Ken Cavanaugh

Nested Class Summary

static class	Guard.Base
static class	Guard.Result

Method Summary

Guard.Result

evaluate(FSM fsm, Input in) Called by the state engine to determine whether a transition is enabled, defered, or disabled.

Method Detail

evaluate

Guard.Result evaluate(FSM fsm,
                      Input in)

Called by the state engine to determine whether a transition is enabled, defered, or disabled. The result is interpreted as follows:

• ENABLED if the transition is ready to proceed
• DISABLED if the transition is not ready to proceed
• DEFERED if the action associated with the transition is to be deferred. This means that the input will not be acted upon, but rather it will be saved for later execution. Typically this is implemented using a CondVar wait, and the blocked thread represents the defered input. The defered input is retried when the thread runs again.

Parameters:

fsm - is the state machine causing this action.

in - is the input that caused the transition.