Java文件监控方式

有三种方式：
1、java common.io    内部实现是遍历的方式，小文件夹的效率还好，比如我测试60G的目录，就很慢很慢了。
2、jdk 7 的watch service    //没有测试
3、jnotify                   直接调用windows的api，效率很高，也很简单，推荐使用。

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common.io
需要java.io 2.1及其以上版本。版本地址如下：
http://commons.apache.org/io/download_io.cgi

import org.apache.commons.io.monitor.FileAlterationListenerAdaptor;
 
/** 
* 自定义文件监听器 
* @author   
* @date    2010-11-16 
* @file    org.demo.file.MyFileListener.java 
*/ 
public class MyFileListener extends FileAlterationListenerAdaptor{  
    @Override 
    public void onFileCreate(File file) {  
        System.out.println("[新建]:" + file.getAbsolutePath());  
    }  
    @Override 
    public void onFileChange(File file) {  
        System.out.println("[修改]:" + file.getAbsolutePath());  
    }  
    @Override 
    public void onFileDelete(File file) {  
        System.out.println("[删除]:" + file.getAbsolutePath());  
    }  
}


import org.apache.commons.io.monitor.FileAlterationMonitor;
import org.apache.commons.io.monitor.FileAlterationObserver;


public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception{
           // 监控目录  
        String rootDir = "d:\\Temp";  
        // 轮询间隔 5 毫秒  
        long interval = 5l;  
        //   
        FileAlterationObserver observer = new FileAlterationObserver(  
                                              rootDir,null,   
                                              null);  
        observer.addListener(new MyFileListener());  
        FileAlterationMonitor monitor = new FileAlterationMonitor(interval,observer);  
        // 开始监控  
        monitor.start(); 
    }
}
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jdk7 watchservice
详见 http://www.cnblogs.com/callwangxiang/archive/2011/08/04/JavaDirectoryWatcherFileWatcher.html
Java SE 7 Tutorial中增加了一个监控目录变更情况的示例，用于介绍其新发布的WatchService API。



但对于用惯了.NET FileWatcher的用户而言，如果用于项目我认为它有两个欠缺：

1、应该提供一个独立线程后台运行机制，让这个监控过程自己在后台转，不影响前端处理

2、 Java不像.NET有内置的源生事件机制，不过可以借助它内置的Observer/Observable对象用观察者模式实现准事件



下面是把Java SE Tutorial示例中无关内容删除，补充上述两个扩展后的实现，因为这个API比较新，也希望能和大家多多探讨：



1、参考.NET定义事件参数对象

package marvellousworks.practicalpattern.concept.unittest;

import java.nio.file.WatchEvent.Kind;

/**
* 文件系统事件类型
* @author wangxiang
*
*/
public final class FileSystemEventArgs {
    private final String fileName;
    private final Kind<?> kind;
   
    public FileSystemEventArgs(String fileName, Kind<?> kind){
        this.fileName = fileName;
        this.kind = kind;
    }
   
    /**
     * 文件的路径
     */
    public String getFileName(){return fileName;}
   
    /**
     * 操作类型：变更、创建、删除
     */
    @SuppressWarnings("rawtypes")
    public Kind getKind(){return kind;}
}


2、定义DirectoryWatcher，用于监控某个文件夹，至于如何扩展FileWatcher则可以在这个基础上通过限定文件名称和操作类型的方式扩展



package marvellousworks.practicalpattern.concept.unittest;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.WatchEvent;
import java.nio.file.WatchEvent.Kind;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.util.Observable;
import java.util.concurrent.Callable;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;

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

/**
* 监控一个目录内文件的更新、创建和删除事件（不包括子目录）
*
* 对于http://download.oracle.com/javase/tutorial/essential/io/notification.html进行了改造
* 使其更接近.NET的DirectoryWatcher使用习惯
*
* 由于java没有类似.NET源生的事件机制
* 因此实现上采用了Java SE自带的Observer/Observable对象对外抛出“假”事件
*
* 适于Java SE 7
*
* @author wangxiang
*
*/
public class DirectoryWatcher extends Observable{

    private WatchService watcher;
    private Path path;
    private WatchKey key;
    private Executor executor = Executors.newSingleThreadExecutor();
   
    FutureTask<Integer> task = new FutureTask<Integer>(
            new Callable<Integer>(){
                public Integer call() throws InterruptedException{
                    processEvents();
                    return Integer.valueOf(0);}});

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

    public DirectoryWatcher(String dir) throws IOException {
        watcher = FileSystems.getDefault().newWatchService();
        path = Paths.get(dir);
        //    监控目录内文件的更新、创建和删除事件
        key = path.register(watcher, ENTRY_MODIFY, ENTRY_CREATE, ENTRY_DELETE);
    }

    /**
     * 启动监控过程
     */
    public void execute(){
        // 通过线程池启动一个额外的线程加载Watching过程
        executor.execute(task);       
    }
   
    /**
     * 关闭后的对象无法重新启动
     * @throws IOException
     */
    public void shutdown() throws IOException {
        watcher.close();
        executor = null;
    }

    /**
     * 监控文件系统事件
     */
    void processEvents() {
        while (true) {
            // 等待直到获得事件信号
            WatchKey signal;
            try {
                signal = watcher.take();
            } catch (InterruptedException x) {
                return;
            }

            for (WatchEvent<?> event : signal.pollEvents()) {
                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();
                notifiy(name.getFileName().toString(), kind);
            }
            //    为监控下一个通知做准备
            key.reset();
        }
    }
   
    /**
     * 通知外部各个Observer目录有新的事件更新
     */
    void notifiy(String fileName, Kind<?> kind){
        // 标注目录已经被做了更改
        setChanged();
        //     主动通知各个观察者目标对象状态的变更
        //    这里采用的是观察者模式的“推”方式
        notifyObservers(new FileSystemEventArgs(fileName, kind));
    }
}


3、单元测试

package marvellousworks.practicalpattern.concept.unittest;

import static org.junit.Assert.*;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Observable;
import java.util.Observer;

import org.junit.Test;
import static java.nio.file.StandardWatchEventKinds.*;

public class DirectoryWatcherFixture {

    private static final String DIR_PATH =System.getProperty("user.dir");
    private static final File DIR = new File(DIR_PATH);
    private static final String SUFFIX = ".txt";
    private static final String PREFIX = "test";
    private static final int ADD_TIMES = 3;

    /**
     * 观察者
     * @author wangxiang
     *
     */
    public class Logger implements Observer{
        @Override
        public void update(Observable observable, Object eventArgs) {
            FileSystemEventArgs args = (FileSystemEventArgs) eventArgs;
            System.out.printf("%s has been %s\n", args.getFileName(), args.getKind());
            assertTrue(args.getFileName().startsWith(PREFIX));
                assertEquals(ENTRY_CREATE, args.getKind());
        }
    }
   
    @Test
    public void testWatchFile() throws IOException, InterruptedException{
        DirectoryWatcher watcher = new DirectoryWatcher(DIR_PATH);
        Logger l1 = new Logger();
        watcher.addObserver(l1);
        watcher.execute();
       
        //    创建一系列临时文件
        List<String> files = new ArrayList<>();
        for(int i=0; i<ADD_TIMES; i++){
            files.add(File.createTempFile(PREFIX, SUFFIX, DIR).toString());
        }
       
        //    延迟等待后台任务的执行
        Thread.sleep(4000);
        watcher.shutdown();
        System.out.println("finished");
    }
}


Console窗口显示的测试内容



test5769907807190550725.txt has been ENTRY_CREATE
test4657672246246330348.txt has been ENTRY_CREATE
test1823102943601166149.txt has been ENTRY_CREATE
finished

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jnotify
详见 http://www.blogjava.net/pengo/archive/2011/01/09/342622.html
jnotify分为64位 和 32位。 详见 http://jnotify.sourceforge.net/
public class Test {

    /**
     * @param args
     */
    public static void main(String[] args) throws Exception{
           // 监控目录  
        String rootDir = "Z:\\";
        String path = rootDir;
        int mask = JNotify.FILE_CREATED | JNotify.FILE_DELETED
                | JNotify.FILE_MODIFIED | JNotify.FILE_RENAMED;
        boolean watchSubtree = true;
        while (true) { //否则一次就完了
            System.out.println("begin watch");
            JNotify.addWatch(path, mask, watchSubtree, new MyJnotifyListner());
            Thread.sleep(10000);
            System.out.println("end watch");
        }
    }

}



import net.contentobjects.jnotify.JNotifyListener;


public class MyJnotifyListner implements JNotifyListener {
    public void fileRenamed(int wd, String rootPath, String oldName,
            String newName) {
        System.out.println("文件：" + rootPath + " : " + oldName + " 重命名为： "
                + newName + "\n");
    }

    public void fileModified(int wd, String rootPath, String name) {
        System.out.println("文件修改 " + rootPath + " : " + name + "\n");
    }

    public void fileDeleted(int wd, String rootPath, String name) {
        System.out.println("删除文件： " + rootPath + " : " + name + "\n");
    }

    public void fileCreated(int wd, String rootPath, String name) {
        System.out.println("新建文件: " + rootPath + " : " + name + "\n");
    }
}