摘要：項目地址，另外知乎同名文章也是我發布的，大家可以多多關注首先觀察控制臺其次再看本地壁紙庫現在進入正題，這個小項目用到了具體版本見，另外還用到了中的線程池阻塞隊列生產消費者模式文件監聽服務，所以至少要求版本為或者以上項目分為個類和一個方法入

項目地址，另外知乎同名文章也是我發布的，大家可以多多關注

首先觀察控制臺

其次再看本地壁紙庫

現在進入正題，這個小項目用到了 Jsoup具體版本見 POM），另外還用到了 JDK中的線程池、阻塞隊列（生產-消費者模式）、NIO2（文件監聽服務 API），所以至少要求 JDK版本為7或者以上

項目分為5個類和一個方法入口類

生產者類（任務：從列表頁拿到詳情頁鏈接并放入阻塞隊列）

public class Producer implements Runnable {

    private String name;
    private BlockingQueue blockingQueue;

    public Producer(String name, BlockingQueue blockingQueue) {
        this.name = name;
        this.blockingQueue = blockingQueue;
    }

    @Override
    public void run() {
        Document doc = null;
        try {
            for(int i = 1; i < 12018; i ++) {
                System.out.println();
                System.out.println();
                System.out.println("current page:" + i);
                System.out.println("-----------------------------------");
                if(i == 1) {
                    doc = Jsoup.connect("https://alpha.wallhaven.cc/latest").get();
                } else {
                    doc = Jsoup.connect("https://alpha.wallhaven.cc/latest?page=" + i).get();
                }
                Element div = doc.getElementById("thumbs");
                Elements sections = div.getElementsByTag("section");
                for (Element ele : sections) {
                    Elements links = ele.getElementsByClass("preview");
                    for (Element e : links) {
                        String href = e.attr("href");
                        blockingQueue.put(href);
                        System.out.println(name + " put " + href);
                    }
                }
            }
            blockingQueue.put("");
            System.out.println(name + " is over");
        } catch (IOException | InterruptedException e) {
            e.printStackTrace();
        } 
    }
}

消費者類（任務：從隊列拿到鏈接并獲取圖片源地址并將下載任務交給一個緩存線程池）

public class Consumer implements Runnable {

    private String name;
    private BlockingQueue blockingQueue;
    private ExecutorService taskPool;

    public Consumer(String name, BlockingQueue blockingQueue, ExecutorService taskPool) {
        this.name = name;
        this.blockingQueue = blockingQueue;
        this.taskPool = taskPool;
    }

    @Override
    public void run() {
        Document doc = null;
        try {
            String href = null;
            while((href = blockingQueue.take()) != "") {
                System.out.println(name + " take " + href);
                doc = Jsoup.connect(href).get();
                Element img = doc.getElementById("wallpaper");
                String src = "https:" + img.attr("src");
                taskPool.submit(new DownloadTask(src));
            }
            System.out.println(name + " is over");
        } catch (IOException | InterruptedException e) {
            e.printStackTrace();
        } 
    }

}

下載任務執行類（任務：下載圖片到本地）

public class DownloadTask implements Runnable {

    private static String path = "C:UsersaiyapengDesktopPaper";
    private String src;
    private String name;

    public DownloadTask(String src) {
        this.src = src;
        int n = src.lastIndexOf("/");
        this.name = src.substring(++n);
    }

    @Override
    public void run() {
        Response res = null;
        try {
            res = Jsoup.connect(src).ignoreContentType(true).timeout(30000).execute();
            byte[] bytes = res.bodyAsBytes();
            File file = new File(path + name);
            if (!file.exists()) {
                RandomAccessFile raf = new RandomAccessFile(file, "rw");
                raf.write(bytes);
                raf.close();
            }
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }

}

監聽服務類（任務：將文件路徑注冊到監聽服務上并開始監聽）

public class ResourceListener {

    private static ExecutorService fixedThreadPool = Executors.newCachedThreadPool();

    private WatchService ws;

    private ResourceListener(String path) {
        try {
            ws = FileSystems.getDefault().newWatchService();
            start();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void start() {
        fixedThreadPool.execute(new Listener(ws));
    }

    public static void addListener(String path) {
        try {
            ResourceListener resourceListener = new ResourceListener(path);
            Path p = Paths.get(path);
            p.register(resourceListener.ws, StandardWatchEventKinds.ENTRY_CREATE);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

}

監聽回調類（任務：執行回調任務）

public class Listener implements Runnable {

    private WatchService service;

    public Listener(WatchService service) {
        this.service = service;
    }

    @Override
    public void run() {
        try {
            while (true) {
                WatchKey watchKey = service.take();
                List> watchEvents = watchKey.pollEvents();
                for (WatchEvent event : watchEvents) {
                    System.err.println(event.context() + "已下載");
                }
                watchKey.reset();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } 
    }
}

方法入口類

public class DownloadTaskExecutor {

    public static void main(String[] args) throws IOException {
        
        ResourceListener.addListener("C:UsersaiyapengDesktopPaper");
    
        BlockingQueue blockingQueue = new SynchronousQueue(true);
        ExecutorService proservice = Executors.newSingleThreadExecutor();
        ExecutorService conservice = Executors.newSingleThreadExecutor();
        ExecutorService taskPool = Executors.newCachedThreadPool();
        proservice.submit(new Producer("Producer", blockingQueue));
        conservice.submit(new Consumer("Consumer", blockingQueue, taskPool));
        proservice.shutdown();
        conservice.shutdown();
    }

}

最后就是設置壁紙庫并設定更換頻率

感謝大家，有問題可以再評論區留言~~