How to recognize changes in log file - logfile

Question

I'm trying to write a java program that reacts if a new entry occures in the file C:/xampp/apache/logs/access.log in order to recognize a new request to my Apache Server.
I used the following code:
public static void monitor() throws IOException {
WatchService watcher = FileSystems.getDefault().newWatchService();
File file = new File("C:/xampp/apache/logs/");
Path dir = file.toPath();
dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY, OVERFLOW);
for (;;) {
// wait for key to be signaled
WatchKey key;
try {
key = watcher.take();
} catch (InterruptedException x) {
return;
}
for (WatchEvent<?> event : key.pollEvents()) {
WatchEvent.Kind<?> kind = event.kind();
// get file name
#SuppressWarnings("unchecked")
WatchEvent<Path> ev = (WatchEvent<Path>) event;
Path fileName = ev.context();
System.out.println(kind.name() + ": " + fileName);
if (kind == OVERFLOW) {
continue;
} else if (kind == ENTRY_CREATE) {
System.out.println("entry created occured");
// process create event
} else if (kind == ENTRY_DELETE) {
// process delete event
} else if (kind == ENTRY_MODIFY && fileName.toString().equals("access.log")) {
System.out.println("entry modified occured");
// process modify event
}
}
// Reset the key -- this step is critical if you want to
// receive further watch events. If the key is no longer valid,
// the directory is inaccessible so exit the loop.
boolean valid = key.reset();
if (!valid) {
break;
}
}
}
But it does not recognize the change in access.log until I manually open the file. Is there something wrong with my code?

Answer 1

There are differents options.
There are two questions that can be kind of similiar, the only difference is that they want to check a whole direcotry instead of just a file, but you could adapt the code to detect if the modified file is the one that you want.
Watching a Directory for Changes in Java
Java detect changes in filesystem
For a specific solution I've found
http://www.rgagnon.com/javadetails/java-0490.html
This code launches a thread that checks the lastModified value of the file, if it's different from the previous one, it means that the file has been modified. I don't know if it's very efficient, check them out.