使用 Java 监视服务监视子文件夹
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Monitor subfolders with a Java watch service
提问by Raja
I am using watchKeyto listen for a file change in a particular folder.
我正在使用watchKey侦听特定文件夹中的文件更改。
Path _directotyToWatch = Paths.get("E:/Raja");
WatchService watcherSvc = FileSystems.getDefault().newWatchService();
WatchKey watchKey = _directotyToWatch.register(watcherSvc, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
while (true) {
watchKey=watcherSvc.take();
for (WatchEvent<?> event: watchKey.pollEvents()) {
WatchEvent<Path> watchEvent = castEvent(event);
System.out.println(event.kind().name().toString() + " " + _directotyToWatch.resolve(watchEvent.context()));
watchKey.reset();
}
}
It working fine for me. If I modify a file in raja folder it gives me the file name with path. But, when I put some files in subfolders like "E:/Raja/Test", it gives me only the path where I put it, not the file name.
它对我来说工作正常。如果我修改 raja 文件夹中的文件，它会给我带路径的文件名。但是，当我把一些文件放在像“E:/Raja/Test”这样的子文件夹中时，它只给我放置它的路径，而不是文件名。
How to get the file name?
如何获取文件名？
回答by informatik01
The reason whyyou're not getting the file name created/modified inside a subfolder is given by Stephen Cin his answer.
Stephen C在他的回答中给出了为什么没有在子文件夹中创建/修改文件名的原因。
Here is a simple example of howto register directoriesand subdirectoriesto watch them for the events you are interested in:
下面是一个简单的示例，说明如何注册目录和子目录以监视它们以查看您感兴趣的事件：
/**
* Register the given directory and all its sub-directories with the WatchService.
*/
private void registerAll(final Path start) throws IOException {
// register directory and sub-directories
Files.walkFileTree(start, 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;
}
});
}
Check out the official Java Tutorials: Watching a Directory for Changes. There you can find very nice explanations and examples with the source code.
查看官方 Java 教程：观察目录的变化。在那里您可以找到非常好的解释和示例以及源代码。
Particularly you'll be interested in this example of how to watch a directory (or directory tree) for changes to files: WatchDir.java.
特别是您会对这个关于如何观察目录（或目录树）的文件更改的示例感兴趣：WatchDir.java。
The method I supplied above was taken from this example (omitting some parts for brevity).
Read the tutorial for the details.
我上面提供的方法取自这个例子（为了简洁省略了一些部分）。
阅读教程了解详情。
回答by Stephen C
The reason you are only seeing an event for "E:/Raja/Test" and not "E:/Raja/Test/Foo.txt" (for example) is that you've only registered the "E:/Raja" directory with the service. This means you will see events on the directory and its immediate members. The "E:/Raja/Test" is a member of the directory, and you are getting events to say that is has been changed ... when files are added to it.
您只看到“E:/Raja/Test”事件而不是“E:/Raja/Test/Foo.txt”（例如）的原因是您只注册了“E:/Raja”目录与服务。这意味着您将看到有关目录及其直接成员的事件。"E:/Raja/Test" 是该目录的一个成员，当文件被添加到它时，你会收到事件说它已经改变了。
The solution is to register all of subdirectories of "E:/Raja" as well ... going as far down the directory hierarchy as you need to go.
解决方案是同时注册“E:/Raja”的所有子目录……在您需要的目录层次结构中尽可能向下。
回答by Nick
I know this is ugly, hopefully somebody has a better answer but you can create a list of every file in every subfolder and there last modified times.
我知道这很难看，希望有人有更好的答案，但您可以创建每个子文件夹中每个文件的列表，并列出最后修改时间。
When you receive ENTRY_CREATE or ENTRY_DELETE compare the folder to your list to figure out which file was changed
当您收到 ENTRY_CREATE 或 ENTRY_DELETE 时，将文件夹与您的列表进行比较，以确定哪个文件被更改
When you receive a ENTRY_MODIFY compare the last modified times.
当您收到 ENTRY_MODIFY 时，请比较上次修改的时间。
Remember to update your list.
记得更新你的清单。
