1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
|
package io.skas.melbjvm.nio2;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.HashMap;
import java.util.Map;
/**
* VisitingWatcher is a watch service that watches a directory tree using the
* SimpleFileVisitor to register directory trees created within the watched
* directory.
*
* @author Szymon Szukalski [szymon.szukalski@gmail.com]
*/
public class VisitingWatcher {
private static final Logger LOG = LoggerFactory.getLogger(VisitingWatcher.class);
private WatchService watchService;
private final Map<WatchKey, Path> watchedPaths = new HashMap<WatchKey, Path>();
private void registerDirectory(Path directory) throws IOException {
WatchKey key = directory.register(
watchService,
StandardWatchEventKinds.ENTRY_CREATE,
StandardWatchEventKinds.ENTRY_MODIFY,
StandardWatchEventKinds.ENTRY_DELETE);
watchedPaths.put(key, directory);
}
private void registerTree(Path startingDirectory) throws IOException {
Files.walkFileTree(startingDirectory, new SimpleFileVisitor<Path>() {
/**
* Invoked for a directory before entries in the directory are visited.
* <p/>
* <p> Unless overridden, this method returns {@link java.nio.file.FileVisitResult#CONTINUE
* CONTINUE}.
*/
@Override
public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
LOG.debug("registering: {}", dir);
registerDirectory(dir);
return FileVisitResult.CONTINUE;
}
});
}
public void watchDirectory(Path directory) throws IOException, InterruptedException {
watchService = FileSystems.getDefault().newWatchService();
registerTree(directory);
while (true) {
// retrieve and remove the next watch key (waits)
final WatchKey key = watchService.take();
// get list of events for the key
for (WatchEvent<?> watchEvent : key.pollEvents()) {
// get the event kind
final WatchEvent.Kind<?> kind = watchEvent.kind();
// get the filename for the event
final WatchEvent<Path> watchEventPath = (WatchEvent<Path>) watchEvent;
final Path filename = watchEventPath.context();
LOG.debug("event: {} filename: {}", kind, filename);
// handle OVERFLOW event
if (kind == StandardWatchEventKinds.OVERFLOW) {
continue;
}
// handle CREATE event
if (kind == StandardWatchEventKinds.ENTRY_CREATE) {
final Path directoryPath = watchedPaths.get(key);
final Path child = directoryPath.resolve(filename);
if (Files.isDirectory(child, LinkOption.NOFOLLOW_LINKS)) {
registerTree(child);
}
}
}
// reset the key
boolean valid = key.reset();
// remove the key from watched paths if the key is not valid
// (if the directory was deleted, for example)
if (!valid) {
watchedPaths.remove(key);
if (watchedPaths.isEmpty()) {
break;
}
}
}
watchService.close();
}
}
|
