org.springframework.statemachine.state.JoinPseudoState.java Source code

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Here is the source code for org.springframework.statemachine.state.JoinPseudoState.java

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/*
 * Copyright 2015 the original author or authors.
 *
 * Licensed 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.springframework.statemachine.state;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.statemachine.StateContext;
import org.springframework.statemachine.guard.Guard;
import org.springframework.statemachine.state.PseudoStateContext.PseudoAction;
import org.springframework.statemachine.support.StateMachineUtils;
import org.springframework.util.Assert;

/**
 * Join implementation of a {@link PseudoState}.
 *
 * @author Janne Valkealahti
 *
 * @param <S> the type of state
 * @param <E> the type of event
 */
public class JoinPseudoState<S, E> extends AbstractPseudoState<S, E> {

    private final static Log log = LogFactory.getLog(JoinPseudoState.class);
    private final List<State<S, E>> joins;
    private final JoinTracker tracker;
    private final List<JoinStateData<S, E>> joinTargets;

    /**
     * Instantiates a new join pseudo state.
     *
     * @param joins the joins
     * @param joinTargets the target states
     */
    public JoinPseudoState(List<State<S, E>> joins, List<JoinStateData<S, E>> joinTargets) {
        super(PseudoStateKind.JOIN);
        this.joins = joins;
        this.joinTargets = joinTargets;
        this.tracker = new JoinTracker();
    }

    @Override
    public State<S, E> entry(StateContext<S, E> context) {
        if (!tracker.isNotified()) {
            return null;
        }
        State<S, E> s = null;
        for (JoinStateData<S, E> c : joinTargets) {
            s = c.getState();
            if (c.guard != null && evaluateInternal(c.guard, context)) {
                break;
            }
        }
        return s;
    }

    @Override
    public void exit(StateContext<S, E> context) {
        tracker.reset();
    }

    /**
     * Gets the join states.
     *
     * @return the joins
     */
    public List<State<S, E>> getJoins() {
        return joins;
    }

    private boolean evaluateInternal(Guard<S, E> guard, StateContext<S, E> context) {
        try {
            return guard.evaluate(context);
        } catch (Throwable t) {
            log.warn("Deny guard due to throw as GUARD should not error", t);
            return false;
        }
    }

    private class JoinTracker {

        private final List<State<S, E>> track;
        private volatile boolean notified = false;

        public JoinTracker() {
            this.track = new ArrayList<State<S, E>>(joins);
            for (State<S, E> tt : joins) {
                final State<S, E> t = tt;
                t.addStateListener(new StateListener<S, E>() {

                    @Override
                    public void onEntry(StateContext<S, E> context) {
                        if (context.getTransition() != null && StateMachineUtils
                                .isPseudoState(context.getTransition().getTarget(), PseudoStateKind.END)) {
                            if (!notified && track.size() > 0) {
                                track.remove(t);
                                if (track.size() == 0) {
                                    notified = true;
                                    notifyContext(new DefaultPseudoStateContext<S, E>(JoinPseudoState.this,
                                            PseudoAction.JOIN_COMPLETED));
                                }
                            }
                        }
                    }

                    @Override
                    public void onExit(StateContext<S, E> context) {
                        if (!notified && track.size() > 0) {
                            track.remove(t);
                            if (track.size() == 0) {
                                notified = true;
                                notifyContext(new DefaultPseudoStateContext<S, E>(JoinPseudoState.this,
                                        PseudoAction.JOIN_COMPLETED));
                            }
                        }
                    }
                });
            }
        }

        void reset() {
            track.clear();
            track.addAll(joins);
            notified = false;
        }

        public boolean isNotified() {
            return notified;
        }
    }

    /**
     * Data class wrapping join {@link State} and {@link Guard}
     * together.
     *
     * @param <S> the type of state
     * @param <E> the type of event
     */
    public static class JoinStateData<S, E> {
        private final StateHolder<S, E> state;
        private final Guard<S, E> guard;

        /**
         * Instantiates a new join state data.
         *
         * @param state the state holder
         * @param guard the guard
         */
        public JoinStateData(StateHolder<S, E> state, Guard<S, E> guard) {
            Assert.notNull(state, "Holder must be set");
            this.state = state;
            this.guard = guard;
        }

        /**
         * Gets the state holder.
         *
         * @return the state holder
         */
        public StateHolder<S, E> getStateHolder() {
            return state;
        }

        /**
         * Gets the state.
         *
         * @return the state
         */
        public State<S, E> getState() {
            return state.getState();
        }

        /**
         * Gets the guard.
         *
         * @return the guard
         */
        public Guard<S, E> getGuard() {
            return guard;
        }
    }
}