Listener di directory in Java

Question

Ho un'applicazione in cui voglio ascoltare le modifiche apportate a una directory specifica. L'applicazione dovrebbe eseguire il ping non appena ci sono file aggiunti, cancellati o aggiornati in quella directory.

Answer 1

È possibile utilizzare JNotify

JNotify è una libreria Java che permettono di applicazioni Java per ascoltare un file eventi di sistema, come ad esempio: file creato File file modificato rinominato File cancellato supportati piattaforme

Windows (2000 o più recente) Note di Windows Linux con supporto INofity (2.6.14 o più recenti) Note Linux Mac OS X (1 0.5 o più recente ) Mac OS nota

Ulteriori informazioni:

Scarica JNotify da here

estrarre la zip, inserire .dll/.so in base alla piattaforma nel tuo percorso lib. e creare una classe fornire jnotify-0.93.jar nel percorso di classe.

codice di esempio:

package org.life.java.stackoverflow.questions; 

import net.contentobjects.jnotify.JNotify; 
import net.contentobjects.jnotify.JNotifyListener; 

/** 
* 
* @author Jigar 
*/ 
public class JNotifyDemo { 

    public void sample() throws Exception { 
     // path to watch 
     String path = System.getProperty("user.home"); 

     // watch mask, specify events you care about, 
     // or JNotify.FILE_ANY for all events. 
     int mask = JNotify.FILE_CREATED 
       | JNotify.FILE_DELETED 
       | JNotify.FILE_MODIFIED 
       | JNotify.FILE_RENAMED; 

     // watch subtree? 
     boolean watchSubtree = true; 

     // add actual watch 
     int watchID = JNotify.addWatch(path, mask, watchSubtree, new Listener()); 

     // sleep a little, the application will exit if you 
     // don't (watching is asynchronous), depending on your 
     // application, this may not be required 
     Thread.sleep(1000000); 

     // to remove watch the watch 
     boolean res = JNotify.removeWatch(watchID); 
     if (!res) { 
      // invalid watch ID specified. 
     } 
    } 

    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) throws Exception { 
     new JNotifyDemo().sample(); 
    } 
} 

uscita:

modified C:\Documents and Settings\jigar: LOCALS~1\Temp\etilqs_4s8ywsvyukghK0uDxRop 
modified C:\Documents and Settings\jigar : LOCALS~1\Temp\etilqs_4s8ywsvyukghK0uDxRop 
modified C:\Documents and Settings\jigar : LOCALS~1\Temp\output1295531079119 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default 
deleted C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001ea9 
created C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001eae 
modified C:\Documents and Settings\jigar : LOCALS~1\Temp\etilqs_04gchL79ZJrpClZIqiom 
modified C:\Documents and Settings\jigar : LOCALS~1\Temp\etilqs_04gchL79ZJrpClZIqiom 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001eae 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001eae 
modified C:\Documents and Settings\jigar : LOCALS~1\Temp\output1295531079119 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Current Session 
deleted C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001ea8 
created C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001eaf 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache 
modified C:\Documents and Settings\jigar : LOCALS~1\Temp\etilqs_04gchL79ZJrpClZIqiom 
modified C:\Documents and Settings\jigar : LOCALS~1\Temp\etilqs_04gchL79ZJrpClZIqiom 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001eaf 
modified C:\Documents and Settings\jigar : Local Settings\Application Data\Google\Chrome\User Data\Default\Cache\f_001eaf 

Answer 2

Jnotify per notifica file in java. Esempio di codice

public void sample() throws Exception { 
     // path to watch  
     String path = System.getProperty("user.home");  
     // watch mask, specify events you care about,  
     // or JNotify.FILE_ANY for all events.  
     int mask = JNotify.FILE_CREATED |     
     JNotify.FILE_DELETED |     
     JNotify.FILE_MODIFIED |     
     JNotify.FILE_RENAMED;  
     // watch subtree? boolean watchSubtree = true;  
     // add actual watch  
     int watchID = JNotify.addWatch(path, mask, watchSubtree, new Listener());  
     // sleep a little, the application will exit if you  
     // don't (watching is asynchronous), depending on your  
     // application, this may not be required  
     Thread.sleep(1000000);  
     // to remove watch the watch  
     boolean res = JNotify.removeWatch(watchID);  
     if (!res) {  
      // invalid watch ID specified.  
      } 
     } 
    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); } 
     } 

Answer 3

Dal momento che Java 1.7 è possibile utilizzare la Watch Service API per registrarsi per gli eventi di directory. Fa parte della libreria Java New I/O (NIO) e non richiede risorse aggiuntive. Un esempio di come utilizzare l'API può essere trovato nel official documentation.

Dopo aver registrato il WatchService è possibile recuperare gli eventi per il percorso di destinazione in questo modo:

for (WatchEvent<?> event: key.pollEvents()) { 
      // 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); 
     }