Package com.complexible.common.base

Class AtomicState<S extends Enum<S>>

java.lang.Object
com.complexible.common.base.AtomicState<S>
public class AtomicState<S extends Enum<S>> extends Object
Represents a mutable state that can be updated exclusively through beginTransitionFrom(Enum[]) and endTransition() calls. Actual states are represented as enumerations. This class guarantees that there will be a single current state at any time and at most one state transition action will be running at any time.
Since:
2.0.3
Version:
3.0
Author:
Evren Sirin

  • Constructor Details

    • AtomicState

      public AtomicState(S theInitState)

  • Method Details

    • newState

      public static <S extends Enum<S>> AtomicState<S> newState(S theInitState)

    • beginTransitionFrom

      public S beginTransitionFrom(S... theStates)
      Starts a transition provided that the current state is one of the specified states. If no initial states are provided then the transition will begin regardless of the current state. This call will block if a current transition is in progress.
      Throws:
      IllegalStateException - if the current state is not a valid initial state for the action

    • tryBeginTransition

      public S tryBeginTransition(S... thePossibleInitialStates)
      Attempts to start a transition "tentatively": that is, it will attempt the transition only if the current state is contained in thePossibleInitialStates; If it is not, this will unroll any action taken, as if the transition was never attempted. If the transition is successful, then the old state will be returned. If it is not successful, then null is returned. This is an inexpensive way of doing idempotent transitions (i.e. only transition to a single state once).
      Parameters:
      thePossibleInitialStates - the possible states that the transaction can be in
      Returns:
      the old state, if the transition has begun, or null if the transition fails

    • endTransition

      public void endTransition(S theFinalState)
      Ends the transition with the given final state. This is equivalent to: try { set(theFinalState); } finally { endTransition(); }
      Parameters:
      theFinalState - the final state

    • endTransition

      public void endTransition()
      Ends the current transition.

    • transitionTo

      public void transitionTo(S theFinalState, S... theInitialStates)
      Performs the transition to a final state. This is equivalent to: beginTransitionFrom(theInitialStates); try { set(theFinalState); } finally { endTransition(); }
      Parameters:
      theFinalState -
      theInitialStates -

    • cancelTransition

      public void cancelTransition()
      Request the cancellation of current transition.

    • isTransitionCanceled

      public boolean isTransitionCanceled()
      Returns true if the current transition is requested to be canceled.

    • get

      public S get()
      Returns the current state.

    • set

      public void set(S theState)
      Sets the current state only if the current thread began a transition.

    • checkState

      public void checkState(S theState)
      Throws IllegalStateException if the current state is not equal to the given state.

    • checkState

      public void checkState(Collection<S> theStates)
      Throws IllegalStateException if the current state is one of the given states.

    • checkStateNot

      public void checkStateNot(S theState)
      Throws IllegalStateException if the current state is equal to the given state.

    • isInTransition

      public boolean isInTransition()
      Returns true if a transition is being performed.