下载时监听文件夹变化

引自: https://www.cnblogs.com/yangzhilong/p/7487220.html

package com.longge.mytest;

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 yangzhilong
 *
 */
public class TestWatchService {
    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<?> event : watchEvents){  
                        //TODO 根据事件类型采取不同的操作。。。。。。。  
                        System.out.println("["+path+"/"+event.context()+"]文件发生了["+event.kind()+"]事件");    
                    }  
                    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) {
            }
        }));
    }
}

引自: https://www.jianshu.com/p/928ce1010407

package service;

import config.Config;
import java.io.IOException;
import java.nio.file.*;
import java.util.List;
import java.util.concurrent.TimeUnit;

public class WatchDirService {
    private WatchService watchService;
    private boolean notDone = true;

    public WatchDirService(String dirPath){
        init(dirPath);
    }

    private void init(String dirPath) {
        Path path = Paths.get(dirPath);
        try {
            watchService = FileSystems.getDefault().newWatchService();  //创建watchService
            path.register(watchService, 
            StandardWatchEventKinds.ENTRY_CREATE,
            StandardWatchEventKinds.ENTRY_MODIFY,
            StandardWatchEventKinds.ENTRY_DELETE); //注册需要监控的事件,ENTRY_CREATE 文件创建,ENTRY_MODIFY 文件修改,ENTRY_MODIFY 文件删除
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void start(){
        System.out.print("watch...");
        while (notDone){
            try {
                WatchKey watchKey = watchService.poll(Config.POLL_TIME_OUT, TimeUnit.SECONDS); 
                if(watchKey != null){
                    List<WatchEvent<?>> events = watchKey.pollEvents();  //获取所有得事件
                    for (WatchEvent event : events){
                        WatchEvent.Kind<?> kind = event.kind(); 
                        if (kind == StandardWatchEventKinds.OVERFLOW){
                            //当前磁盘不可用
                            continue;
                        }
                        WatchEvent<Path> ev = event;
                        Path path = ev.context();
                        if(kind == StandardWatchEventKinds.ENTRY_CREATE){
                            System.out.println("create " + path.getFileName());
                        }else if(kind == StandardWatchEventKinds.ENTRY_MODIFY){
                            System.out.println("modify " + path.getFileName());
                        }else if(kind == StandardWatchEventKinds.ENTRY_DELETE){
                            System.out.println("delete " + path.getFileName());
                        }
                    }
                    if(!watchKey.reset()){ 
                        //已经关闭了进程
                        System.out.println("exit watch server");
                        break;
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
                return;
            }
        }
    }
}

作者：DrJasonZhang
链接：https://www.jianshu.com/p/928ce1010407
來源：简书
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