Java之——JDK7中的WatchService

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JDK7中的WatchService能够实现文件变更监听，使用示例如下代码所示：

package com.binghe.jdk7.listener;

import java.io.IOException;
import java.nio.file.FileSystems;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardWatchEventKinds;
import java.nio.file.WatchEvent;
import java.nio.file.WatchKey;
import java.nio.file.WatchService;
import java.util.List;

/**
 * 测试JDK的WatchService监听文件变化
 * @author binghe
 *
 */
public class Watcher {
    public static void main(String[] args) throws IOException {
        // 需要监听的文件目录（只能监听目录）
        String path = "d:/test";
        
        WatchService watchService = FileSystems.getDefault().newWatchService();
        Path p = Paths.get(path);
        p.register(watchService, StandardWatchEventKinds.ENTRY_MODIFY,  
                StandardWatchEventKinds.ENTRY_DELETE,  
                StandardWatchEventKinds.ENTRY_CREATE);  
        
        Thread thread = new Thread(() -> {
            try {  
                while(true){  
                    WatchKey watchKey = watchService.take();  
                    List<WatchEvent<?>> watchEvents = watchKey.pollEvents();  
                    for(WatchEvent<?> watchEvent : watchEvents){  
                    	WatchEvent.Kind<?> kind = watchEvent.kind();
                    	System.out.println("当前的文件为：" + path+"/"+watchEvent.context() + ", 进行的操作类型为：" + kind);
                    	if (kind == StandardWatchEventKinds.ENTRY_CREATE) {
                    		System.out.println("新建文件: "+watchEvent.context()+" 次数: " + watchEvent.count());
                        } else if (kind == StandardWatchEventKinds.ENTRY_DELETE) {
                        	System.out.println("删除文件: "+ watchEvent.context()+", 次数: " + watchEvent.count());
                        } else if (kind == StandardWatchEventKinds.ENTRY_MODIFY) {
                        	System.out.println("修改文件: "+watchEvent.context()+", 次数: " + watchEvent.count());
                        } else if (kind == StandardWatchEventKinds.OVERFLOW) {
                        	System.out.println("overflow: "+watchEvent.context()+", 次数: " + watchEvent.count());
                        }
                    }  
                    watchKey.reset();  
                }  
            } catch (InterruptedException e) {  
                e.printStackTrace();  
            }
        });
        thread.setDaemon(false);
        thread.start();
        
        // 增加jvm关闭的钩子来关闭监听
        Runtime.getRuntime().addShutdownHook(new Thread(() -> {
            try {
                watchService.close();
            } catch (Exception e) {
            }
        }));
    }
}