Java 中的目录监听器

Question

我有一个应用程序，我想在其中监听对特定目录所做的任何更改。一旦该目录中添加、删除或更新了任何文件，应用程序应该立即对我进行 ping 操作。

Answer 1

从 Java 1.7 开始，您可以使用 Watch Service API 来注册对于目录事件。它是 Java 新 I/O (NIO) 的一部分图书馆，不需要任何额外的资源。如何使用 API 的示例可以在官方文档中找到。

注册 WatchService 后，您可以检索目标路径的事件，如下所示：

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);
        }

Answer 2

您可以使用 JNotify

JNotify是一个java库，允许java应用程序监听文件
系统事件，例如： 文件已创建
文件已修改 文件已重命名 文件
已删除支持的平台

Windows（2000 或更高版本）Windows 注释
支持 INofity 的 Linux（2.6.14 或
较新版本）Linux 注释 Mac OS X（10.5 或
较新）Mac OS 注释

更多信息：

从 此处

解压 zip，根据平台将 .dll/.so 放入您的 lib 路径中。并在类路径中创建一个提供jnotify-0.93.jar的类。

示例代码：

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();
    }
}

输出：

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 3

java中的Jnotify用于文件通知。代码示例

   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);    }  
        }