/* *  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.mina.statemachine;import java.util.Collection;import java.util.Collections;import java.util.HashMap;import java.util.LinkedList;import java.util.Map;import java.util.Stack;import org.apache.mina.statemachine.context.StateContext;import org.apache.mina.statemachine.event.Event;import org.apache.mina.statemachine.event.UnhandledEventException;import org.apache.mina.statemachine.transition.Transition;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * Represents a complete state machine. Contains a collection of {@link State} * objects connected by {@link Transition}s. Normally you wouldn't create  * instances of this class directly but rather use the  * {@link org.apache.mina.statemachine.annotation.State} annotation to define * your states and then let {@link StateMachineFactory} create a  * {@link StateMachine} for you. * * @author The Apache MINA Project (dev@mina.apache.org) * @version $Rev: 641052 $, $Date: 2008-03-25 23:22:35 +0100 (Tue, 25 Mar 2008) $ */public class StateMachine {    private static final Logger log = LoggerFactory.getLogger(StateMachine.class);    private static final String CALL_STACK = StateMachine.class.getName() + ".callStack";    private final State startState;    private final Map<String, State> states;    private final ThreadLocal<Boolean> processingThreadLocal = new ThreadLocal<Boolean>() {        protected Boolean initialValue() {            return Boolean.FALSE;        }    };    private final ThreadLocal<LinkedList<Event>> eventQueueThreadLocal = new ThreadLocal<LinkedList<Event>>() {        protected LinkedList<Event> initialValue() {            return new LinkedList<Event>();        }    };        /**     * Creates a new instance using the specified {@link State}s and start     * state.     *      * @param states the {@link State}s.     * @param startStateId the id of the start {@link State}.     */    public StateMachine(State[] states, String startStateId) {        this.states = new HashMap<String, State>();        for (State s : states) {            this.states.put(s.getId(), s);        }        this.startState = getState(startStateId);    }    /**     * Creates a new instance using the specified {@link State}s and start     * state.     *      * @param states the {@link State}s.     * @param startStateId the id of the start {@link State}.     */    public StateMachine(Collection<State> states, String startStateId) {        this(states.toArray(new State[0]), startStateId);    }        /**     * Returns the {@link State} with the specified id.     *      * @param id the id of the {@link State} to return.     * @return the {@link State}     * @throws NoSuchStateException if no matching {@link State} could be found.     */    public State getState(String id) throws NoSuchStateException {        State state = states.get(id);        if (state == null) {            throw new NoSuchStateException(id);        }        return state;    }    /**     * Returns an unmodifiable {@link Collection} of all {@link State}s used by     * this {@link StateMachine}.     *      * @return the {@link State}s.     */    public Collection<State> getStates() {        return Collections.unmodifiableCollection(states.values());    }        /**     * Processes the specified {@link Event} through this {@link StateMachine}.     * Normally you wouldn't call this directly but rather use     * {@link StateMachineProxyBuilder} to create a proxy for an interface of     * your choice. Any method calls on the proxy will be translated into     * {@link Event} objects and then fed to the {@link StateMachine} by the     * proxy using this method.     *      * @param event the {@link Event} to be handled.     */    public void handle(Event event) {        StateContext context = event.getContext();        synchronized (context) {            LinkedList<Event> eventQueue = eventQueueThreadLocal.get();            eventQueue.addLast(event);            if (processingThreadLocal.get()) {                /*                 * This thread is already processing an event. Queue this                  * event.                 */                if (log.isDebugEnabled()) {                    log.debug("State machine called recursively. Queuing event " + event                            + " for later processing.");                }            } else {                processingThreadLocal.set(true);                try {                    if (context.getCurrentState() == null) {                        context.setCurrentState(startState);                    }                    processEvents(eventQueue);                } finally {                    processingThreadLocal.set(false);                }            }        }    }    private void processEvents(LinkedList<Event> eventQueue) {        while (!eventQueue.isEmpty()) {            Event event = eventQueue.removeFirst();            StateContext context = event.getContext();            handle(context.getCurrentState(), event);        }    }        private void handle(State state, Event event) {        StateContext context = event.getContext();        for (Transition t : state.getTransitions()) {            if (log.isDebugEnabled()) {                log.debug("Trying transition " + t);            }            try {                if (t.execute(event)) {                    if (log.isDebugEnabled()) {                        log.debug("Transition " + t + " executed successfully.");                    }                    setCurrentState(context, t.getNextState());                    return;                }            } catch (BreakAndContinueException bace) {                if (log.isDebugEnabled()) {                    log.debug("BreakAndContinueException thrown in "                             + "transition " + t                            + ". Continuing with next transition.");                }            } catch (BreakAndGotoException bage) {                State newState = getState(bage.getStateId());                if (bage.isNow()) {                    if (log.isDebugEnabled()) {                        log.debug("BreakAndGotoException thrown in "                                 + "transition " + t + ". Moving to state "                                + newState.getId() + " now.");                    }                    setCurrentState(context, newState);                    handle(newState, event);                } else {                    if (log.isDebugEnabled()) {                        log.debug("BreakAndGotoException thrown in "                                 + "transition " + t + ". Moving to state "                                + newState.getId() + " next.");                    }                    setCurrentState(context, newState);                }                return;            } catch (BreakAndCallException bace) {                State newState = getState(bace.getStateId());                Stack<State> callStack = getCallStack(context);                State returnTo = bace.getReturnToStateId() != null                     ? getState(bace.getReturnToStateId())                     : context.getCurrentState();                callStack.push(returnTo);                if (bace.isNow()) {                    if (log.isDebugEnabled()) {                        log.debug("BreakAndCallException thrown in "                                 + "transition " + t + ". Moving to state "                                + newState.getId() + " now.");                    }                    setCurrentState(context, newState);                    handle(newState, event);                } else {                    if (log.isDebugEnabled()) {                        log.debug("BreakAndCallException thrown in "                                 + "transition " + t + ". Moving to state "                                + newState.getId() + " next.");                    }                    setCurrentState(context, newState);                }                return;            } catch (BreakAndReturnException bare) {                Stack<State> callStack = getCallStack(context);                State newState = callStack.pop();                if (bare.isNow()) {                    if (log.isDebugEnabled()) {                        log.debug("BreakAndReturnException thrown in "                                 + "transition " + t + ". Moving to state "                                + newState.getId() + " now.");                    }                    setCurrentState(context, newState);                    handle(newState, event);                } else {                    if (log.isDebugEnabled()) {                        log.debug("BreakAndReturnException thrown in "                                 + "transition " + t + ". Moving to state "                                + newState.getId() + " next.");                    }                    setCurrentState(context, newState);                }                return;            }        }        /*         * No transition could handle the event. Try with the parent state if         * there is one.         */        if (state.getParent() != null) {            handle(state.getParent(), event);        } else {            throw new UnhandledEventException(event);        }    }    private Stack<State> getCallStack(StateContext context) {        @SuppressWarnings("unchecked")        Stack<State> callStack = (Stack<State>) context.getAttribute(CALL_STACK);        if (callStack == null) {            callStack = new Stack<State>();            context.setAttribute(CALL_STACK, callStack);        }        return callStack;    }    private void setCurrentState(StateContext context, State newState) {        if (newState != null) {            if (log.isDebugEnabled()) {                if (newState != context.getCurrentState()) {                    log.debug("Leaving state " + context.getCurrentState().getId());                    log.debug("Entering state " + newState.getId());                }            }            context.setCurrentState(newState);        }    }    }