在java watchservice中实现重命名和删除

Question

我尝试在javaWatchService中实现简单的重命名。

我的假设是：当文件被重命名时，会执行三个操作

• 删除文件xxx
• 创建文件yyy
• 修改文件yyy

以下是我的代码：

MyWatcher.java

import java.io.IOException;
    import java.nio.file.FileSystems;
    import java.nio.file.Path;
    import java.nio.file.Paths;
    import java.nio.file.StandardWatchEventKinds;
    import java.nio.file.WatchEvent;
    import java.nio.file.WatchKey;
    import java.nio.file.WatchService;
    import java.util.ArrayList;
    import java.util.List;
    public class MyWatcher {
        @SuppressWarnings("rawtypes")
        public static void main(String[] strings) {
            Path myWatchPath = Paths.get("D:\log4j");
            long preventDuplicateTime = 0;
            FileDelete onDelete = new FileDelete();//this object must be thread safe
            List<String> notifications = new ArrayList<String>();
            WatchService myPathWatchService = null;
            try {
                myPathWatchService = FileSystems.getDefault().newWatchService();
            } catch (IOException e) {
                e.printStackTrace();
            }
            try {
                myWatchPath.register(myPathWatchService,
                        StandardWatchEventKinds.ENTRY_CREATE,
                        StandardWatchEventKinds.ENTRY_DELETE,
                        StandardWatchEventKinds.ENTRY_MODIFY);
            } catch (IOException e) {
                e.printStackTrace();
            }
            boolean isKeyValid = true;
            while (isKeyValid) {
                WatchKey myPathWatchKey = null;
                try {
                    myPathWatchKey = myPathWatchService.take();
                } catch (InterruptedException e) {
                    e.printStackTrace();// throw
                }
                    for (WatchEvent watchEvent : myPathWatchKey.pollEvents()) {
                        //WatchEvent.Kind kind = watchEvent.kind();
                        if (StandardWatchEventKinds.ENTRY_CREATE.equals(watchEvent
                                .kind())) {
                            String fileName = watchEvent.context().toString();
                            if(onDelete.status == -1)
                             System.out.println("File Created:" + fileName + " "
                                    + watchEvent.context());
                            else{
                                if(onDelete.status == 0){
                                    onDelete.createdTime = System.nanoTime();
                                if (onDelete.deletedTime / 10000000 == onDelete.createdTime / 10000000) {
                                    onDelete.createdFile = watchEvent.context().toString();
                                    onDelete.status++;
                                    notifications.add("File Created:" + fileName);
                                }else{
                                    for (String string : notifications) {
                                        System.out.println(string);
                                    }
                                    notifications = new ArrayList<String>();
                                    System.out.println("File Created:" + fileName + " "
                                            + watchEvent.context());
                                    onDelete = new FileDelete();  //Time duration not close (seems not renamed)
                                }
                                }else{
                                    //this should never come here!!
                                    onDelete = new FileDelete();
                                }
                            }
                        }
                        if (StandardWatchEventKinds.ENTRY_DELETE.equals(watchEvent
                                .kind())) {
                            String fileName = watchEvent.context().toString();
                            if(onDelete.status == -1){
                                onDelete = new FileDelete();
                                onDelete.status++;
                                onDelete.deletedFile = watchEvent.context().toString();
                                onDelete.deletedTime = System.nanoTime();
                                notifications.add("File deleted:" + fileName);
                            }
                            //System.out.println("File deleted:" + fileName);   // push to notfication to array for later use
                        }
                        if (StandardWatchEventKinds.ENTRY_MODIFY.equals(watchEvent
                                .kind())) {
                            long current = System.nanoTime();
                            String fileName = watchEvent.context().toString();
                            if(!(preventDuplicateTime/10000000 == current/10000000))
                                notifications.add("File modified:" + fileName);
                            preventDuplicateTime = (System.nanoTime());
                            onDelete.modifiedFile= fileName;
                            onDelete.modifiedTime =System.nanoTime();
                            if(onDelete.status != 1){
                                for (String messages : notifications) {
                                    System.out.println(messages);
                                }
                            onDelete= new FileDelete();
                            notifications = new ArrayList<String>();
                            }
                            else if(onDelete.createdFile.equals(onDelete.modifiedFile))
                                    if( onDelete.createdTime /10000000 == onDelete.modifiedTime/10000000){
                                        System.out.println("File renamed:" + fileName);
                                        onDelete = new FileDelete();
                                        notifications = new ArrayList<String>();
                             }
                        }
                    /*}*/
                }
                isKeyValid = myPathWatchKey.reset();
            }
        }
    }

FileRename.java

public class FileRename {
    int status =-1;
    String deletedFile = "";
    long deletedTime = 0 ;
    String createdFile = "";
    long createdTime =0 ;
    String modifiedFile = "";
    long modifiedTime = 0 ;
}

它在重命名操作中显示得很好，但问题是我不知道如何显示onDelete。因为每次删除都会被推送到通知中！！或者帮我实现重命名！！

*注意：请不要建议使用第三方罐子！（因为它们中的大多数，如JNotify，都依赖于操作系统）

Answer 1

请在下面找到独立于操作系统的解决方案无法工作的一些解释。以及为什么Java WatchService的事件粒度对于您想要实现的目标来说太弱。

根据可用的事件（CREATE、MODIFY、DELETE），您无法确定发生了哪个操作。

以Linux机器为例

创建一些测试文件

touch /tmp/stackoverflow/foo /tmp/stackoverflow/foo2

执行以下命令

rm foo && cp foo2 bar && echo foo > bar

这将创建以下事件（使用WatchDir.java监控）

ENTRY_DELETE ..:..:.. [.........]: /tmp/stackoverflow/foo
ENTRY_CREATE 20:09:37 [rw.rw.rw.]: /tmp/stackoverflow/bar
ENTRY_MODIFY 20:09:37 [rw.rw.rw.]: /tmp/stackoverflow/bar

根据您对事件顺序的假设，这将是rename操作。

Wheras mv bar foobar创建以下事件。

ENTRY_DELETE ..:..:.. [.........]: /tmp/stackoverflow/bar
ENTRY_CREATE 19:55:37 [rw.rw.rw.]: /tmp/stackoverflow/foobar

现在窗口机也是如此

创建一些测试文件

rem.>c:/temp/stackoverflow/foo
rem.>c:/tmp/stackoverflow/foo2

执行以下命令

del foo
copy foo2 bar

这将创建以下事件

ENTRY_DELETE ..:..:.. [.........]: c:tempstackoverflowfoo
ENTRY_CREATE 19:59:10 [.........]: c:tempstackoverflowbar
ENTRY_MODIFY 19:59:10 [.........]: c:tempstackoverflowbar

根据您对事件顺序的假设，这将是rename操作。

Wheras ren bar foobar在这种情况下创建相同的事件顺序。

ENTRY_DELETE ..:..:.. [.........]: c:tempstackoverflowbar
ENTRY_CREATE 20:02:41 [.........]: c:tempstackoverflowfoobar
ENTRY_MODIFY 20:02:41 [.........]: c:tempstackoverflowfoobar

与Linux机器上的iwatch /tmp/stackoverflow/相反，您可以准确地确定发生了什么。

执行命令rm foo && cp foo2 bar && echo foo > bar产生以下不合理的事件。

[31/Mär/2015 20:25:40] IN_DELETE /tmp/stackoverflow//foo
[31/Mär/2015 20:25:40] * /tmp/stackoverflow//foo is deleted
[31/Mär/2015 20:25:40] IN_CREATE /tmp/stackoverflow//bar
[31/Mär/2015 20:25:40] IN_CLOSE_WRITE /tmp/stackoverflow//bar
[31/Mär/2015 20:25:40] * /tmp/stackoverflow//bar is closed
[31/Mär/2015 20:25:40] IN_CLOSE_WRITE /tmp/stackoverflow//bar
[31/Mär/2015 20:25:40] * /tmp/stackoverflow//bar is closed

而CCD_ 8创建了以下不确定事件

[31/Mär/2015 20:27:10] IN_MOVED_FROM /tmp/stackoverflow//bar
[31/Mär/2015 20:27:10] IN_MOVED_TO /tmp/stackoverflow//foobar
[31/Mär/2015 20:27:10] * /tmp/stackoverflow//bar is moved to /tmp/stackoverflow//foobar

编辑相关的Java源代码以确认我的解释。（在纯Java中）无法确定是重命名了一个文件，还是删除了一个，同时创建了另一个。

WindowsWatchService.java第462行

// Translate file change action into watch event
private WatchEvent.Kind<?> translateActionToEvent(int action)
{
    switch (action) {
        case FILE_ACTION_MODIFIED :
            return StandardWatchEventKinds.ENTRY_MODIFY;
        case FILE_ACTION_ADDED :
        case FILE_ACTION_RENAMED_NEW_NAME :
            return StandardWatchEventKinds.ENTRY_CREATE;
        case FILE_ACTION_REMOVED :
        case FILE_ACTION_RENAMED_OLD_NAME :
            return StandardWatchEventKinds.ENTRY_DELETE;
        default :
            return null;  // action not recognized
    }
}

LinuxWatchService.java线路376

/**
 * map inotify event to WatchEvent.Kind
 */
private WatchEvent.Kind<?> maskToEventKind(int mask) {
    if ((mask & IN_MODIFY) > 0)
        return StandardWatchEventKinds.ENTRY_MODIFY;
    if ((mask & IN_ATTRIB) > 0)
        return StandardWatchEventKinds.ENTRY_MODIFY;
    if ((mask & IN_CREATE) > 0)
        return StandardWatchEventKinds.ENTRY_CREATE;
    if ((mask & IN_MOVED_TO) > 0)
        return StandardWatchEventKinds.ENTRY_CREATE;
    if ((mask & IN_DELETE) > 0)
        return StandardWatchEventKinds.ENTRY_DELETE;
    if ((mask & IN_MOVED_FROM) > 0)
        return StandardWatchEventKinds.ENTRY_DELETE;
    return null;
}