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/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
package org.apache.qpid.server.store;
import java.util.EnumMap;
import java.util.Map;
public class StateManager
{
private State _state = State.INITIAL;
private EventListener _eventListener;
private static final Map<State,Map<State, Transition>> _validTransitions = new EnumMap<State, Map<State, Transition>>(State.class);
static class Transition
{
private final Event _event;
private final State _endState;
private final State _startState;
public Transition(State startState, State endState, Event event)
{
_event = event;
_startState = startState;
_endState = endState;
Map<State, Transition> stateTransitions = _validTransitions.get(startState);
if(stateTransitions == null)
{
stateTransitions = new EnumMap<State, Transition>(State.class);
_validTransitions.put(startState, stateTransitions);
}
stateTransitions.put(endState, this);
}
public Event getEvent()
{
return _event;
}
public State getStartState()
{
return _startState;
}
public State getEndState()
{
return _endState;
}
}
public static final Transition CONFIGURE = new Transition(State.INITIAL, State.CONFIGURING, Event.BEFORE_INIT);
public static final Transition CONFIGURE_COMPLETE = new Transition(State.CONFIGURING, State.CONFIGURED, Event.AFTER_INIT);
public static final Transition RECOVER = new Transition(State.CONFIGURED, State.RECOVERING, Event.BEFORE_ACTIVATE);
public static final Transition ACTIVATE = new Transition(State.RECOVERING, State.ACTIVE, Event.AFTER_ACTIVATE);
public static final Transition CLOSE_ACTIVE = new Transition(State.ACTIVE, State.CLOSING, Event.BEFORE_CLOSE);
public static final Transition CLOSE_QUIESCED = new Transition(State.QUIESCED, State.CLOSING, Event.BEFORE_CLOSE);
public static final Transition CLOSE_COMPLETE = new Transition(State.CLOSING, State.CLOSED, Event.AFTER_CLOSE);
public static final Transition QUIESCE = new Transition(State.ACTIVE, State.QUIESCING, Event.BEFORE_PASSIVATE);
public static final Transition QUIESCE_COMPLETE = new Transition(State.QUIESCING, State.QUIESCED, Event.BEFORE_PASSIVATE);
public static final Transition RESTART = new Transition(State.QUIESCED, State.RECOVERING, Event.BEFORE_ACTIVATE);
public StateManager(final EventManager eventManager)
{
this(new EventListener()
{
@Override
public void event(Event event)
{
eventManager.notifyEvent(event);
}
});
}
public StateManager(EventListener eventListener)
{
_eventListener = eventListener;
}
public synchronized State getState()
{
return _state;
}
public synchronized void stateTransition(final State current, final State desired)
{
if (_state != current)
{
throw new IllegalStateException("Cannot transition to the state: " + desired + "; need to be in state: " + current
+ "; currently in state: " + _state);
}
attainState(desired);
}
public synchronized void attainState(State desired)
{
Transition transition = null;
final Map<State, Transition> stateTransitionMap = _validTransitions.get(_state);
if(stateTransitionMap != null)
{
transition = stateTransitionMap.get(desired);
}
if(transition == null)
{
throw new IllegalStateException("No valid transition from state " + _state + " to state " + desired);
}
_state = desired;
_eventListener.event(transition.getEvent());
}
public synchronized boolean isInState(State testedState)
{
return _state.equals(testedState);
}
public synchronized boolean isNotInState(State testedState)
{
return !isInState(testedState);
}
public synchronized void checkInState(State checkedState)
{
if (isNotInState(checkedState))
{
throw new IllegalStateException("Unexpected state. Was : " + _state + " but expected : " + checkedState);
}
}
}
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