在java watchservice中实现重命名和删除

Question

我试图在java WatchService中实现简单的重命名.

我的假设是:重命名文件时,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 ;
}

它完美地显示了重命名操作,但问题是我无法想象如何显示onDelete.因为每次删除都被推送到通知中!! 或者帮我实现重命名!!

*注意请不要建议第三方罐子!(因为大多数人,如JNotify,都依赖于操作系统)

Answer 1

请在下面找到一些解释为什么独立于操作系统的解决方案无效 为什么Java的事件粒度WatchService太弱而无法实现.

根据可用事件(CREATE,MODIFY,DELETE),您无法确定发生了哪个操作.

以下是Linux机器上的示例

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监视)

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

在您假设事件顺序之后,这将是一个rename动作.

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

对于Window机器现在也一样

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:\temp\stackoverflow\foo
ENTRY_CREATE 19:59:10 [.........]: c:\temp\stackoverflow\bar
ENTRY_MODIFY 19:59:10 [.........]: c:\temp\stackoverflow\bar

在您假设事件顺序之后,这将是一个rename动作.

ren bar foobar在这种情况下,Wheras 创建相同的事件顺序.

ENTRY_DELETE ..:..:.. [.........]: c:\temp\stackoverflow\bar
ENTRY_CREATE 20:02:41 [.........]: c:\temp\stackoverflow\foobar
ENTRY_MODIFY 20:02:41 [.........]: c:\temp\stackoverflow\foobar

与iwatch /tmp/stackoverflow/Linux机器相反,您可以确切地确定发生了什么.

执行命令rm foo && cp foo2 bar && echo foo > bar 会产生以下inotify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mv bar foobar创建以下inotify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.没有办法(在普通的Java中)找出是重命名一个文件还是删除一个文件而另一个文件被创建(同时).

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第376行

/**
 * 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;
}