jetty-deploy-manager/src/main/java/org/eclipse/jetty/deploy/AppLifeCycle.java

// ========================================================================
// Copyright (c) Webtide LLC
// ------------------------------------------------------------------------
// All rights reserved. This program and the accompanying materials
// are made available under the terms of the Eclipse Public License v1.0
// and Apache License v2.0 which accompanies this distribution.
//
// The Eclipse Public License is available at 
// http://www.eclipse.org/legal/epl-v10.html
//
// The Apache License v2.0 is available at
// http://www.apache.org/licenses/LICENSE-2.0.txt
//
// You may elect to redistribute this code under either of these licenses. 
// ========================================================================
package org.eclipse.jetty.deploy;

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

/**
 * The lifecycle of an App in the {@link DeploymentManager}.
 * <p>
 * <img src="doc-files/AppLifeCycle.png">
 */
public class AppLifeCycle
{
    /**
     * State that an {@link App} can be in, as a result of traversal via the {@link AppLifeCycle}
     * <p>
     * <img src="doc-files/AppLifeCycle.png">
     */
    public enum State
    {
        /**
         * The web app is not available.
         * 
         * It has likely not been deployed, or has failed deployment.
         */
        UNAVAILABLE,

        /**
         * The web app has been deployed, but not yet made available for incoming requests.
         */
        DEPLOYED,

        /**
         * The web app has been started and is ready to accept requests on the expected context.
         */
        STARTED;
    }

    public enum Phase
    {
        DEPLOY, START, STOP, UNDEPLOY;
    }

    public class Step
    {
        private State from;
        private Phase phase;
        private State to;

        public Step(State from, Phase phase, State to)
        {
            this.from = from;
            this.phase = phase;
            this.to = to;
        }

        public State getFrom()
        {
            return from;
        }

        public Phase getPhase()
        {
            return phase;
        }

        public State getTo()
        {
            return to;
        }
    }

    public List<Step> getSteps(State from, State to)
    {
        if (from == to)
        {
            return Collections.emptyList();
        }

        List<Step> steps = new ArrayList<Step>();

        /*
         * This nastiness can be replaced with a simple BFS Graph impl w/ edge defs.
         */
        switch (from)
        {
            case UNAVAILABLE:
                switch (to)
                {
                    case DEPLOYED:
                        steps.add(new Step(from,Phase.DEPLOY,to));
                        return steps;
                    case STARTED:
                        steps.add(new Step(from,Phase.DEPLOY,State.DEPLOYED));
                        steps.add(new Step(State.DEPLOYED,Phase.START,to));
                        return steps;
                }
                break;
            case DEPLOYED:
                switch (to)
                {
                    case UNAVAILABLE:
                        steps.add(new Step(from,Phase.UNDEPLOY,to));
                        return steps;
                    case STARTED:
                        steps.add(new Step(from,Phase.START,to));
                        return steps;
                }
            case STARTED:
                switch (to)
                {
                    case DEPLOYED:
                        steps.add(new Step(from,Phase.STOP,to));
                        return steps;
                    case UNAVAILABLE:
                        steps.add(new Step(from,Phase.STOP,State.DEPLOYED));
                        steps.add(new Step(State.DEPLOYED,Phase.UNDEPLOY,to));
                        return steps;
                }
        }

        return steps;
    }
}