com.garyclayburg.filesystem.WatchDir.java Source code

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Here is the source code for com.garyclayburg.filesystem.WatchDir.java

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/*
 * VisualSync - a tool to visualize user data synchronization
 * Copyright (c) 2014 Gary Clayburg
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 */

package com.garyclayburg.filesystem;

import com.garyclayburg.attributes.AttributeService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;

import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.HashMap;
import java.util.Map;

import static java.nio.file.LinkOption.NOFOLLOW_LINKS;
import static java.nio.file.StandardWatchEventKinds.*;

/*
 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * Example to watch a directory (or tree) for changes to files.
 */
@Component
public class WatchDir implements Runnable {

    private WatchService watcher;
    private Map<WatchKey, Path> keys;
    private boolean recursive;
    private Path watchDir;
    private boolean trace = false;

    @SuppressWarnings("UnusedDeclaration")
    private static final Logger log = LoggerFactory.getLogger(WatchDir.class);

    @Qualifier("attributeService")
    @Autowired
    private AttributeService attributeService;

    @SuppressWarnings("unchecked")
    static <T> WatchEvent<T> cast(WatchEvent<?> event) {
        return (WatchEvent<T>) event;
    }

    /**
     * Register the given directory with the WatchService
     */
    private void register(Path dir) throws IOException {
        WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
        if (trace) {
            Path prev = keys.get(key);
            if (prev == null) {
                log.debug("register: {}", dir);
            } else {
                if (!dir.equals(prev)) {
                    log.debug("update: {} -> {}", prev, dir);
                }
            }
        }
        keys.put(key, dir);
    }

    /**
     * Register the given directory, and all its sub-directories, with the
     * WatchService.
     */
    private void registerAll(final Path start) throws IOException {
        // register directory and sub-directories
        Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
                register(dir);
                return FileVisitResult.CONTINUE;
            }
        });
    }

    /**
     * Creates a WatchService and registers the given directory
     */
    public WatchDir(Path dir, boolean recursive) throws IOException {
        this.recursive = recursive;
        this.watchDir = dir;
    }

    private void init(Path dir, boolean recursive) throws IOException {
        this.watcher = FileSystems.getDefault().newWatchService();
        this.keys = new HashMap<>();

        if (recursive) {
            log.info("Scanning {} ...\n", dir);
            registerAll(dir);
            log.debug("Scanning Done.");
        } else {
            register(dir);
        }

        // enable trace after initial registration
        this.trace = true;
    }

    @Override
    public void run() {
        try {
            init(watchDir, recursive);
            for (;;) {

                log.debug("Listening for File Events...");
                // wait for key to be signalled
                WatchKey key;
                try {
                    key = watcher.take();
                } catch (InterruptedException x) {
                    return;
                }

                Path dir = keys.get(key);
                if (dir == null) {
                    log.warn("WatchKey not recognized!! " + key);
                    continue;
                }
                for (WatchEvent<?> event : key.pollEvents()) {
                    WatchEvent.Kind kind = event.kind();

                    // TBD - provide example of how OVERFLOW event is handled
                    if (kind == OVERFLOW) {
                        continue;
                    }

                    // Context for directory entry event is the file name of entry
                    WatchEvent<Path> ev = cast(event);
                    Path name = ev.context();
                    Path child = dir.resolve(name);

                    // print out event
                    log.info("{}: {}", event.kind().name(), child);
                    if (kind == ENTRY_CREATE || kind == ENTRY_MODIFY) {
                        attributeService.reloadGroovyClass(child);
                    } else if (kind == ENTRY_DELETE) {
                        attributeService.removeGroovyClass(child);
                    }

                    // if directory is created, and watching recursively, then
                    // register it and its sub-directories
                    if (recursive && (kind == ENTRY_CREATE)) {
                        try {
                            if (Files.isDirectory(child, NOFOLLOW_LINKS)) {
                                registerAll(child);
                            }
                        } catch (IOException x) {
                            log.warn("Cannot register possible new directory for groovy changes: {}", child);
                        }
                    }
                }

                // reset key and remove from set if directory no longer accessible
                boolean valid = key.reset();
                if (!valid) {
                    keys.remove(key);

                    // all directories are inaccessible
                    if (keys.isEmpty()) {
                        break;
                    }
                }
            }
            log.info("Stopped listening for file events");
        } catch (IOException e) {
            log.warn("Could not start File Watch service", e);
        }
    }

}