org.alfresco.util.exec.RuntimeExecShutdownBean.java Source code

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Here is the source code for org.alfresco.util.exec.RuntimeExecShutdownBean.java

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/*
 * Copyright (C) 2005-2010 Alfresco Software Limited.
 *
 * This file is part of Alfresco
 *
 * Alfresco is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Alfresco is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with Alfresco. If not, see <http://www.gnu.org/licenses/>.
 */
package org.alfresco.util.exec;

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

import org.springframework.extensions.surf.util.AbstractLifecycleBean;
import org.alfresco.util.exec.RuntimeExec.ExecutionResult;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.context.ApplicationEvent;

/**
 * This bean executes a list of shutdown commands when either the VM shuts down
 * or the application context closes.  In both cases, the commands are only
 * executed if the application context was started.
 * 
 * @author Derek Hulley
 */
public class RuntimeExecShutdownBean extends AbstractLifecycleBean {
    private static Log logger = LogFactory.getLog(RuntimeExecShutdownBean.class);

    /** the commands to execute on context closure or VM shutdown */
    private List<RuntimeExec> shutdownCommands;
    /** the registered shutdown hook */
    private Thread shutdownHook;
    /** ensures that commands don't get executed twice */
    private boolean executed;

    /**
     * Initializes the bean with empty defaults, i.e. it will do nothing
     */
    public RuntimeExecShutdownBean() {
        this.shutdownCommands = Collections.emptyList();
        this.executed = false;
    }

    /**
     * Set the commands to execute, in sequence, when the application context
     * is initialized.
     * 
     * @param startupCommands list of commands
     */
    public void setShutdownCommands(List<RuntimeExec> startupCommands) {
        this.shutdownCommands = startupCommands;
    }

    private synchronized void execute() {
        // have we already done this?
        if (executed) {
            return;
        }
        executed = true;
        for (RuntimeExec command : shutdownCommands) {
            ExecutionResult result = command.execute();
            // check for failure
            if (!result.getSuccess()) {
                logger.error("Shutdown command execution failed.  Continuing with other commands.: \n" + result);
            }
        }
        // done
        if (logger.isDebugEnabled()) {
            logger.debug("Executed shutdown commands");
        }
    }

    /**
     * The thread that will call the shutdown commands.
     * 
     * @author Derek Hulley
     */
    private class ShutdownThread extends Thread {
        private ShutdownThread() {
            super(RuntimeExecShutdownBean.class.getName());
            this.setDaemon(true);
        }

        @Override
        public void run() {
            execute();
        }
    }

    @Override
    protected void onBootstrap(ApplicationEvent event) {
        // register shutdown hook
        shutdownHook = new ShutdownThread();
        Runtime.getRuntime().addShutdownHook(shutdownHook);

        if (logger.isDebugEnabled()) {
            logger.debug("Registered shutdown hook");
        }
    }

    @Override
    protected void onShutdown(ApplicationEvent event) {
        // remove shutdown hook and execute
        if (shutdownHook != null) {
            // execute
            execute();
            // remove hook
            try {
                Runtime.getRuntime().removeShutdownHook(shutdownHook);
            } catch (IllegalStateException e) {
                // VM is already shutting down
            }
            shutdownHook = null;

            if (logger.isDebugEnabled()) {
                logger.debug("Deregistered shutdown hook");
            }
        }
    }

}