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An event driven framework
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package com.kaka.util;

import java.io.File;
import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import static java.nio.file.StandardWatchEventKinds.ENTRY_CREATE;
import static java.nio.file.StandardWatchEventKinds.ENTRY_DELETE;
import static java.nio.file.StandardWatchEventKinds.ENTRY_MODIFY;
import static java.nio.file.StandardWatchEventKinds.OVERFLOW;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * 文件变动监控
 *
 * @author zkpursuit
 */
public class FileWatcher implements Runnable {

    private final WatchService watcher = FileSystems.getDefault().newWatchService();
    private boolean watchFlag;
    private final WatchCallBack callback;

    /**
     * 构造方法
     *
     * @param watchDir 监控目录
     * @param descendants 是否监控目录下的子孙目录
     * @param callback 文件监控回调
     * @throws IOException IO流异常
     */
    public FileWatcher(String watchDir, boolean descendants, WatchCallBack callback) throws IOException {
        this.callback = callback;
        if (descendants) {
            File dir = new File(watchDir);
            List dirs = FileUtils.getDirectories(dir, true);
            for (File file : dirs) {
                String absPath = file.getAbsolutePath();
                Path path = Paths.get(absPath);
                path.register(watcher, ENTRY_CREATE, OVERFLOW, ENTRY_MODIFY, ENTRY_DELETE);
            }
        } else {
            Path path = Paths.get(watchDir);
            path.register(watcher, ENTRY_CREATE, OVERFLOW, ENTRY_MODIFY, ENTRY_DELETE);
        }
        watchFlag = true;
    }

    /**
     * 停止文件监控
     */
    public void stop() {
        watchFlag = false;
    }

    public void close() throws IOException {
        stop();
        watcher.close();
    }

    @Override
    public void run() {
        while (watchFlag) {
            if (watcher == null) {
                return;
            }
            WatchKey signal;
            try {
                signal = watcher.take();
                Path watchDirPath = (Path) signal.watchable();
                signal.pollEvents().forEach((WatchEvent event) -> {
                    WatchEvent.Kind kind = event.kind();
                    Path fileNamePath = (Path) event.context();
                    if (callback != null) {
                        callback.call(kind, watchDirPath, fileNamePath);
                    }
                });
                signal.reset();
            } catch (InterruptedException ex) {
                Logger.getLogger(FileWatcher.class.getName()).log(Level.SEVERE, null, ex);
            }
        }
    }

    /**
     * 文件变动回调
     */
    public interface WatchCallBack {

        /**
         * 监控文件变动的回调
         *
         * @param kind 文件变动的类型
         * @param watchDirPath 变化的目录
         * @param fileNamePath 变化的文件
         */
        void call(WatchEvent.Kind kind, Path watchDirPath, Path fileNamePath);

    }

}