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The official Couchbase JVM Core IO Library
/**
* Copyright (C) 2014 Couchbase, Inc.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALING
* IN THE SOFTWARE.
*/
package com.couchbase.client.core.state;
import com.couchbase.client.core.logging.CouchbaseLogger;
import com.couchbase.client.core.logging.CouchbaseLoggerFactory;
import rx.Observable;
import rx.subjects.BehaviorSubject;
/**
* Abstract {@link Stateful} implementation which acts like a simple state machine.
*
* This class is thread safe, so state transitions can be issued from any thread without any further synchronization.
*
* @author Michael Nitschinger
* @since 1.0
*/
public class AbstractStateMachine implements Stateful {
/**
* The logger used.
*/
private static final CouchbaseLogger LOGGER = CouchbaseLoggerFactory.getInstance(Stateful.class);
/**
* The observable which emits all the subsequent state changes.
*/
private final BehaviorSubject observable;
/**
* The current state of the state machine.
*/
private volatile S currentState;
/**
* Creates a new state machine.
*
* @param initialState the initial state of the state machine.
*/
protected AbstractStateMachine(final S initialState) {
currentState = initialState;
observable = BehaviorSubject.create(currentState);
}
@Override
public final Observable states() {
return observable;
}
@Override
public final S state() {
return currentState;
}
@Override
public final boolean isState(final S state) {
return currentState == state;
}
@Override
public boolean hasSubscribers() {
return observable.hasObservers();
}
/**
* Transition into a new state.
*
* This method is intentionally not public, because the subclass should only be responsible for the actual
* transitions, the other components only react on those transitions eventually.
*
* @param newState the states to transition into.
*/
protected void transitionState(final S newState) {
if (newState != currentState) {
if (LOGGER.isTraceEnabled()) {
LOGGER.trace("State (" + getClass().getSimpleName() + ") " + currentState + " -> " + newState);
}
currentState = newState;
observable.onNext(newState);
}
}
}