我试图在MacOS（High Sierra）上设置WatchService，除非我重命名dir，否则它似乎正常工作。作为一个例子，我重命名＆＃34;测试＆＃34;到＆＃34;你好＆＃34;而这就是我得到的：
ENTRY_CREATE: /Users/david/Desktop/watchme/hello
update: /Users/david/Desktop/watchme/test -> /Users/david/Desktop/watchme/hello
ENTRY_DELETE: /Users/david/Desktop/watchme/test
我希望看到：
register: /Users/david/Desktop/watchme/hello
但这并没有发生，所以当我修改＆＃34; hello＆＃34;内的任何内容时，我得到的唯一回应是：
ENTRY_MODIFY: /Users/david/Desktop/watchme/hello
没有关于＆＃34;你好＆＃34;
内的文件或文件夹我直接从Oracle复制了以下代码，除了对attrs进行硬编码以外，我可以在Idea中运行它：
import java.nio.file.*;
import static java.nio.file.StandardWatchEventKinds.*;
import static java.nio.file.LinkOption.*;
import java.nio.file.attribute.*;
import java.io.*;
import java.util.*;
/**
* Example to watch a directory (or tree) for changes to files.
*/
public class WatchDir {
private final WatchService watcher;
private final Map<WatchKey,Path> keys;
private final boolean recursive;
private boolean trace = false;
@SuppressWarnings("unchecked")
private static <T> WatchEvent<T> cast(WatchEvent<?> event) {
return (WatchEvent<T>)event;
}
/**
* Register the given directory with the WatchService
*/
private void register(Path dir) throws IOException {
WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
if (trace) {
Path prev = keys.get(key);
if (prev == null) {
System.out.format("register: %s\n", dir);
} else {
if (!dir.equals(prev)) {
System.out.format("update: %s -> %s\n", prev, dir);
}
}
}
keys.put(key, dir);
}
/**
* 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
{
register(dir);
return FileVisitResult.CONTINUE;
}
});
}
/**
* Creates a WatchService and registers the given directory
*/
private WatchDir(Path dir, boolean recursive) throws IOException {
this.watcher = FileSystems.getDefault().newWatchService();
this.keys = new HashMap<>();
this.recursive = recursive;
if (recursive) {
System.out.format("Scanning %s ...\n", dir);
registerAll(dir);
System.out.println("Done.");
} else {
register(dir);
}
// enable trace after initial registration
this.trace = true;
}
/**
* Process all events for keys queued to the watcher
*/
private void processEvents() {
for (;;) {
// wait for key to be signalled
WatchKey key;
try {
key = watcher.take();
} catch (InterruptedException x) {
return;
}
Path dir = keys.get(key);
if (dir == null) {
System.err.println("WatchKey not recognized!!");
continue;
}
for (WatchEvent<?> event: key.pollEvents()) {
WatchEvent.Kind kind = event.kind();
// TBD - provide example of how OVERFLOW event is handled
if (kind == OVERFLOW) {
continue;
}
// Context for directory entry event is the file name of entry
WatchEvent<Path> ev = cast(event);
Path name = ev.context();
Path child = dir.resolve(name);
// print out event
System.out.format("%s: %s\n", event.kind().name(), child);
if(child.toString().contains("testdir")) {
System.out.println("This is an update");
}
// if directory is created, and watching recursively, then
// register it and its sub-directories
if (recursive && (kind == ENTRY_CREATE)) {
try {
if (Files.isDirectory(child, NOFOLLOW_LINKS)) {
registerAll(child);
}
} catch (IOException x) {
// ignore to keep sample readbale
}
}
}
// reset key and remove from set if directory no longer accessible
boolean valid = key.reset();
if (!valid) {
keys.remove(key);
// all directories are inaccessible
if (keys.isEmpty()) {
break;
}
}
}
}
private static void usage() {
System.err.println("usage: java WatchDir [-r] dir");
System.exit(-1);
}
@SuppressWarnings("ParameterCanBeLocal")
public static void main(String[] args) throws IOException {
// parse arguments
args = new String[2]; // Added for debug
args[0] = "-r"; // Added for debug
args[1] = "/Users/david/Desktop/watchme"; // Added for debug
if (args.length == 0 || args.length > 2)
usage();
boolean recursive = false;
int dirArg = 0;
if (args[0].equals("-r")) {
if (args.length < 2)
usage();
recursive = true;
dirArg++;
}
// register directory and process its events
Path dir = Paths.get(args[dirArg]);
new WatchDir(dir, recursive).processEvents();
}
}
答案 0 :(得分：1)
这是一个有趣的问题。我尝试在自己的Mac上获得相同的结果。
当我们将 test 重命名为 hello 时，操作系统首先创建 hello ，然后删除 test ，两者都< em> watchme 和 test 将获得活动。 watchme 文件夹的WatchKey获取ENTRY_CREATE和ENTRY_DELETE事件。 在此步骤中，虽然新的目录名称为 hello ，但在此代码之后
WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
我们获得的密钥仍然是 test 的监视密钥，这就是我们在控制台中看到更新日志的原因。
ENTRY_CREATE: /Users/david/Desktop/watchme/hello
update: /Users/david/Desktop/watchme/test -> /Users/david/Desktop/watchme/hello
ENTRY_DELETE: /Users/david/Desktop/watchme/test
这是有趣的事情。当输入目录是 hello 时，为什么我们得到 test 的watchKey。当我调试代码时，请在
处停止它WatchKey key = dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
收到 hello 的ENTRY_CREATE事件一段时间后，我得到 hello 的密钥而不是 test 的密钥和注册日志不更新日志。当调用dir.register方法时，我们似乎无法立即看到 hello 文件夹。我不知道操作系统在重命名文件夹时会做什么，希望别人回复。
这是我在processEvents添加了测试代码的日志，您可以亲自尝试。
private void processEvents() {
for (; ; ) {
// wait for key to be signalled
WatchKey key;
try {
key = watcher.take();
} catch (InterruptedException x) {
return;
}
Path dir = keys.get(key);
if (dir == null) {
System.err.println("WatchKey not recognized!!");
continue;
} else {
System.out.println("CurrentDir=" + dir.getFileName() + " keySize=" + keys.size() + " valid=" + key.isValid());
}
for (WatchEvent<?> event : key.pollEvents()) {
WatchEvent.Kind kind = event.kind();
// TBD - provide example of how OVERFLOW event is handled
if (kind == OVERFLOW) {
continue;
}
// Context for directory entry event is the file name of entry
WatchEvent<Path> ev = cast(event);
Path name = ev.context();
Path child = dir.resolve(name);
// print out event
System.out.format("%s: %s\n", event.kind().name(), child);
// if directory is created, and watching recursively, then
// register it and its sub-directories
if (recursive && (kind == ENTRY_CREATE)) {
try {
if (Files.isDirectory(child, NOFOLLOW_LINKS)) {
registerAll(child);
}
} catch (IOException x) {
// ignore to keep sample readbale
}
}
}
// reset key and remove from set if directory no longer accessible
boolean valid = key.reset();
if (!valid) {
System.out.println("Remove From keys");
keys.remove(key);
// all directories are inaccessible
if (keys.isEmpty()) {
break;
}
}
}
}