I would like to know how to efficiently implement filesystem changes in java? Say I got a file in a folder and modify that file. I would like to be notified by java about th
Take a look at JNotify, which performs this type of monitoring.
Java 7 will have some more advanced APIs (WatchService) for this sort of work which will eliminate polling on the OSes that support this.
There is an Apache package that does file system monitoring: commons.io.monitor.
Documentation
An example
From what I can tell, you will still need to poll albeit you have control over the frequency.
I doubt that there is a pure java way to do this. Operating systems offer APIs to monitor file system a activity. You will probably need to call those APIs.
Use JNotify, All you need to do is add jnotify.jar in buildpath and put two dll files i.e jnotify.dll jnotify_64bit.dll and inside lib of jdk. A demo program is
package jnotify;
import net.contentobjects.jnotify.JNotify;
import net.contentobjects.jnotify.JNotifyListener;
public class MyJNotify {
public void sample() throws Exception {
String path = "Any Folder location here which you want to monitor";
System.out.println(path);
int mask = JNotify.FILE_CREATED | JNotify.FILE_DELETED
| JNotify.FILE_MODIFIED | JNotify.FILE_RENAMED;
boolean watchSubtree = true;
int watchID = JNotify
.addWatch(path, mask, watchSubtree, new Listener());
Thread.sleep(1000000);
boolean res = JNotify.removeWatch(watchID);
if (!res) {
System.out.println("Invalid");
}
}
class Listener implements JNotifyListener {
public void fileRenamed(int wd, String rootPath, String oldName,
String newName) {
print("renamed " + rootPath + " : " + oldName + " -> " + newName);
}
public void fileModified(int wd, String rootPath, String name) {
print("modified " + rootPath + " : " + name);
}
public void fileDeleted(int wd, String rootPath, String name) {
print("deleted " + rootPath + " : " + name);
}
public void fileCreated(int wd, String rootPath, String name) {
print("created " + rootPath + " : " + name);
}
void print(String msg) {
System.err.println(msg);
}
}
public static void main(String[] args) {
try {
new MyJNotify().sample();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}