我可以使用 WatchService(不是整个目录)监视单个文件的更改吗? [英] Can I watch for single file change with WatchService (not the whole directory)?

问题描述

当我尝试注册文件而不是目录时，抛出 java.nio.file.NotDirectoryException.我可以监听单个文件的变化，而不是整个目录吗?

When I'm trying to register a file instead of a directory java.nio.file.NotDirectoryException is thrown. Can I listen for a single file change, not the whole directory?

推荐答案

只需过滤目录中所需文件的事件:

Just filter the events for the file you want in the directory:

final Path path = FileSystems.getDefault().getPath(System.getProperty("user.home"), "Desktop");
System.out.println(path);
try (final WatchService watchService = FileSystems.getDefault().newWatchService()) {
    final WatchKey watchKey = path.register(watchService, StandardWatchEventKinds.ENTRY_MODIFY);
    while (true) {
        final WatchKey wk = watchService.take();
        for (WatchEvent<?> event : wk.pollEvents()) {
            //we only register "ENTRY_MODIFY" so the context is always a Path.
            final Path changed = (Path) event.context();
            System.out.println(changed);
            if (changed.endsWith("myFile.txt")) {
                System.out.println("My file has changed");
            }
        }
        // reset the key
        boolean valid = wk.reset();
        if (!valid) {
            System.out.println("Key has been unregisterede");
        }
    }
}

这里我们检查修改后的文件是否是myFile.txt"，如果是则做任何事情.

Here we check whether the changed file is "myFile.txt", if it is then do whatever.

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