监视目录和子目录以在Java中创建，修改和更改

Question

I have make some code for detect changed in directory C:/java/newfolder it working good. i have given below.

import java.nio.file.*;
import java.util.List;

public class DirectoryWatchExample {
public static void testForDirectoryChange(Path myDir){

        try {
           WatchService watcher = myDir.getFileSystem().newWatchService();
           myDir.register(watcher, StandardWatchEventKinds.ENTRY_CREATE,
           StandardWatchEventKinds.ENTRY_DELETE, StandardWatchEventKinds.ENTRY_MODIFY);

           WatchKey watckKey = watcher.take();

           List<WatchEvent<?>> events = watckKey.pollEvents();
           for (WatchEvent event : events) {
                if (event.kind() == StandardWatchEventKinds.ENTRY_CREATE) {
                    System.out.println("Created: " + event.context().toString());
                }
                if (event.kind() == StandardWatchEventKinds.ENTRY_DELETE) {
                    System.out.println("Delete: " + event.context().toString());
                }
                if (event.kind() == StandardWatchEventKinds.ENTRY_MODIFY) {
                    System.out.println("Modify: " + event.context().toString());
                }
            }

        } catch (Exception e) {
            System.out.println("Error: " + e.toString());
        }
}

public static void main (String[] args) {
    Path myDir = Paths.get("c:/java/newfolder/");
    //define a folder root
    testForDirectoryChange(myDir);

}
} 

now i watching only the directory. But i need to watch only the all sub directory.

for ex : c:/java/newfolder/folder1, c:/java/newfolder/folder2, c:/java/newfolder/folder3......etc

i given examples above sub directory

c:/java/newfolder/*..

i need to watch the all sub directory give me some solutions ?

Answer 1

What you want to do is register the WatchService recursively and continue to register it upon subsequent ENTRY_CREATE events. A complete example is provided by Oracle here: http://docs.oracle.com/javase/tutorial/essential/io/examples/WatchDir.java

Normally I wouldn't place a post with a single link, however I doubt Oracle will be taking down a fairly basic tutorial and the answer is far too verbose. Just in case though, examples are easily found by searching for "java watchservice recursive".

Answer 2

Here is what I came with..

    final WatchService watcher = FileSystems.getDefault().newWatchService();

    final SimpleFileVisitor<Path> fileVisitor = new SimpleFileVisitor<Path>(){
        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException
        {
            dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);

            return FileVisitResult.CONTINUE;
        }
    };

    Files.walkFileTree(Paths.get("/directory/to/monitor"), fileVisitor);

Answer 3

I'm not familiar with the Path API, so take the following with a grain of salt.

You're registering one directory for monitoring, and will receive notifications whenever one of its direct descendants is modified / created / deleted.

The first thing you need to do is register all of its subdirectories for watching:

// Used to filter out non-directory files.
// This might need to filter '.' and '..' out, not sure whether they're returned.
public class DirectoryFilter implements FileFilter {
    public boolean accept(File file) {
        return file.isDirectory();
    }
}


// Add this at the end of your testForDirectoryChange method
for(File dir: myDir.toFile().listFiles(new DirectoryFilter())) {
    testForDirectoryChange(dir.toPath());
}

This will recursively explore your file structure and register every directory for watching. Note that if your directory tree is too deep, recursion might not be an acceptable solution and you might need to 'iterify' it.

The second thing you need to do is, whenever you receive a directory creation event, not forget to register the new directory for monitoring.

That's how I'd do it anyway, but not having a valid Java 1.7 installation at hand, I can't test it. Do let me know if it works!

Answer 4

So what you want is listing the files/subdirectories within a directory? You can use:

File dir = new File("c:/java/newfolder/");
File[] files = dir.listFiles();

listFiles() gives you the Files in a directory or null it it's not a directory.

Then you can do:

for (File file: files){
     if (file.listFiles != null){
          //It's a subdirectory
          File [] subdirFiles = file.listfiles;
     }
}