Java实现高速视频下载示例代码

public class MultiThreadDownloader {
    private static final int THREAD_COUNT = 8; // 根据网络情况调整
    
    public void download(String fileUrl, String savePath) throws Exception {
        long fileSize = getFileSize(fileUrl);
        long blockSize = fileSize / THREAD_COUNT;
        
        ExecutorService executor = Executors.newFixedThreadPool(THREAD_COUNT);
        List<Future<?>> futures = new ArrayList<>();
        
        for (int i = 0; i < THREAD_COUNT; i++) {
            long startPos = i * blockSize;
            long endPos = (i == THREAD_COUNT - 1) ? fileSize - 1 : (i + 1) * blockSize - 1;
            
            futures.add(executor.submit(() -> {
                downloadBlock(fileUrl, savePath, startPos, endPos, i);
            }));
        }
        
        // 等待所有线程完成
        for (Future<?> future : futures) {
            future.get();
        }
        executor.shutdown();
        
        mergeFiles(savePath); // 合并临时文件
    }
    
    private long getFileSize(String fileUrl) throws IOException {
        HttpURLConnection conn = (HttpURLConnection) new URL(fileUrl).openConnection();
        conn.setRequestMethod("HEAD");
        return conn.getContentLengthLong();
    }
}

public class ResumableDownloader {
    private Map<Integer, Long> progressMap = new ConcurrentHashMap<>();
    private String tempDir = "download_tmp/";
    
    public void downloadWithResume(String fileUrl, String savePath) {
        // 检查已有进度
        loadProgress();
        
        // 每个线程检查自己的下载进度
        // ... 类似多线程下载，但起始位置从progressMap中读取
        
        // 定期保存进度
        saveProgress();
    }
    
    private void saveProgress() {
        // 实现进度保存逻辑，可以保存到文件或数据库
    }
    
    private void loadProgress() {
        // 实现进度加载逻辑
    }
}

public class FastFileWriter {
    private static final int BUFFER_SIZE = 8 * 1024; // 8KB缓冲区
    
    public void writeBlock(String path, long position, InputStream input) throws IOException {
        try (RandomAccessFile raf = new RandomAccessFile(path, "rw");
             BufferedInputStream bis = new BufferedInputStream(input, BUFFER_SIZE)) {
            
            raf.seek(position);
            byte[] buffer = new byte[BUFFER_SIZE];
            int len;
            
            while ((len = bis.read(buffer)) != -1) {
                raf.write(buffer, 0, len);
                // 更新进度
            }
        }
    }
}

public class NetworkOptimizer {
    public static HttpURLConnection configureConnection(String url) throws IOException {
        HttpURLConnection conn = (HttpURLConnection) new URL(url).openConnection();
        
        // 重要优化参数
        conn.setRequestProperty("Accept-Encoding", "identity"); // 禁用压缩
        conn.setConnectTimeout(15000); // 15秒连接超时
        conn.setReadTimeout(30000);    // 30秒读取超时
        conn.setRequestProperty("Connection", "Keep-Alive");
        conn.setRequestProperty("User-Agent", "Mozilla/5.0");
        
        return conn;
    }
}

int optimalThreads = Math.max(1, NetworkSpeedTester.getOptimalThreadCount());

MappedByteBuffer buffer = new RandomAccessFile(file, "rw")
    .getChannel()
    .map(FileChannel.MapMode.READ_WRITE, position, blockSize);

try (FileChannel destChannel = new FileOutputStream(file, true).getChannel()) {
    destChannel.transferFrom(Channels.newChannel(inputStream), position, Long.MAX_VALUE);
}

conn.setRequestProperty("Accept-Encoding", "gzip");

public class HighSpeedVideoDownloader {
    private static final String TEMP_DIR = "tmp_downloads/";
    
    public static void main(String[] args) {
        String videoUrl = "http://example.com/video.mp4";
        String savePath = "downloaded_video.mp4";
        
        try {
            new HighSpeedVideoDownloader().download(videoUrl, savePath);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    public void download(String fileUrl, String savePath) throws Exception {
        // 1. 创建临时目录
        createTempDir();
        
        // 2. 获取文件信息
        long fileSize = getFileSize(fileUrl);
        int threadCount = calculateOptimalThreadCount(fileSize);
        
        // 3. 分块下载
        downloadInParallel(fileUrl, savePath, fileSize, threadCount);
        
        // 4. 合并文件
        mergeFiles(savePath);
        
        // 5. 清理临时文件
        cleanTempFiles();
    }
    
    // 其他具体方法实现...
}