java 多线程下载网络图片、视频等

客官°小女子只卖身不卖艺 2024-03-23 13:32 117阅读 0赞

#### 多线程下载网络图片、视频等 ####

*  一、使用准备
 *  二、一个文件实现多线程下载
 *  三、多个文件实现多线程
 *  四、封装使用示例

--------------------

## 一、使用准备 ##

创建一个StartThread 类继承 Runnable 实现多线程

import java.io.File;
    import java.io.InputStream;
    import java.io.RandomAccessFile;
    import java.net.HttpURLConnection;
    import java.net.URL;
    
    public class StartThread implements Runnable {
        
        private String urlLocation;
    
        private String filePath;
    
        private long start;
    
        private long end;
    
        public StartThread(String urlLocation, String filePath, long start, long end) {
        
            this.urlLocation = urlLocation;
            this.filePath = filePath;
            this.start = start;
            this.end = end;
        }
    
        @Override
        public void run() {
        
            try {
        
    
                System.out.println("进入多线程方法");
    
                HttpURLConnection conn = getHttp();
    
                conn.setRequestProperty("Range", "bytes=" + start + "-" + end);
                System.out.println("图片名称-->" + filePath);
    
                File file = new File(filePath);
                RandomAccessFile out = null;
    
                if (file != null) {
        
                    out = new RandomAccessFile(file, "rwd");
                }
    
                out.seek(start);
                InputStream in = conn.getInputStream();
    
                byte[] b = new byte[1024];
                int len = 0;
                while ((len = in.read(b)) != -1) {
        
                    out.write(b, 0, len);
                }
                in.close();
                out.close();
    
    
            } catch (Exception e) {
        
                System.out.println("download fail");
                e.printStackTrace();
    
            }
    
        }
    
        /**
         * 创建连接
         *
         * @return
         */
        public HttpURLConnection getHttp() {
        
            URL url = null;
            HttpURLConnection conn = null;
            try {
        
    
                if (urlLocation != null) {
        
                    url = new URL(urlLocation);
                }
                conn = (HttpURLConnection) url.openConnection();
                conn.setReadTimeout(5000);
                conn.setRequestMethod("GET");
            } catch (Exception e) {
        
                System.out.println("getHttp error");
            }
            return conn;
        }
    
    }

## 二、一个文件实现多线程下载 ##

> 例如：下载一个视频的时候，文件很大却又想下载快些就可以使用多线程进行下载。多线程的方式把一个视频查分成多个视频进行下载，加快视频的下载速度。

import java.io.IOException;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    
    
    public class CreateThread {
        
        /**
         * 实现多线程 方法
         * @param urlLocation //网络图片地址    //  一个图片使用
         * @param filePath
         * @param poolLength
         * @throws IOException
         */
        public void getFileWithThreadPool(String urlLocation,String filePath, int poolLength) throws IOException{
        
    
            ExecutorService threadPool = Executors.newFixedThreadPool(poolLength);
            /**
             * 下载一个文件多线程下载(一个文件很大 可以由多个线程一起下载)
             */
            long len = getContentLength(urlLocation);
            System.out.println("一个文件大小--》"+len+"--线程数--》"+poolLength);
    
            for(int i=0;i<poolLength;i++){
        
    
                long start=i*len/poolLength;
                long end = (i+1)*len/poolLength-1;
    
                System.out.println("start-->"+start+"--end-->"+end);
                if(i==poolLength-1){
        
                    end =len;
                    System.out.println("len 赋值");
                }
    
                //创建多个线程
                StartThread download=new StartThread(urlLocation, filePath, start,end);
                threadPool.execute(download);
    
            }
    
            //让线程执行完自动关闭
            threadPool.shutdown();
            System.err.println("分配线程 任务结束");
        }
    
    
        /**
         * 获取文件的大小 （单位 byte）
         * @param urlLocation
         * @return
         * @throws IOException
         */
        private static long getContentLength(String urlLocation) throws IOException{
        
            URL url = null;
            if (urlLocation != null)
            {
        
                url = new URL(urlLocation);
            }
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            long len = conn.getContentLength();
    
            return len;
        }
    
    
    
        public static void main(String[] args) {
        
            try {
        
    
                //一个文件  多线程下载
    //            String url = "http://img.tupianzj.com/uploads/allimg/140716/3-140G61501440-L.jpg";
                String url = "https://resource.meihua.info/2SxYJ5jka40dYgykSYASyV3Rrik=/lkbiIFctwfhJpPG2epYX_iOTOSS6";
    
                CreateThread createThread = new CreateThread();
                // 网络文件url --- 存放路径 --- 创建的线程数
                createThread.getFileWithThreadPool(url, "D:/usr/share/", 3);
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }
    }

## 三、多个文件实现多线程 ##

> 例如：实现多个文件同时下载，通过爬虫的方式，或者其他渠道获得到的图片、视频路径(多个)，如果成千上百个图片、视频还好你可以等一会，但是上万个，就算一个文件一秒，你也不想等把，如果是视频呢，所以就总结了一下，使用多线程的方式，同时下载多个文件。既加快速度页，又节省时间

import java.io.IOException;
    import java.net.HttpURLConnection;
    import java.net.URL;
    import java.util.concurrent.ExecutorService;
    import java.util.concurrent.Executors;
    
    //同时下载多个文件
    public class MoreFileCreateThread {
        
        /**
         * 实现多线程 方法
         *
         * @param urlLocation //网络图片地址    多个图片用逗号(,)隔开 使用 同时下载多个文件
         * @param filePath
         * @param poolLength
         * @throws IOException
         */
        public void getFileWithThreadPool(String urlLocation, String filePath, int poolLength) throws IOException {
        
    
            ExecutorService threadPool = Executors.newFixedThreadPool(poolLength);
    
    
            /**
             * 同时下载多个文件
             */
            String[] arrayStrings = urlLocation.split(",");
            poolLength = arrayStrings.length;
    
            System.out.println("线程数" + poolLength);
    
            //也可以写一个固定的线程数  一个线程里面执行一份部分下载
    
            for (int a = 0; a < arrayStrings.length; a++) {
        
                System.out.println(a + "长度" + arrayStrings[a]);
                long len = getContentLength(arrayStrings[a]);
    
                StartThread download = new StartThread(arrayStrings[a], filePath + a + ".jpg", 0, len);
                threadPool.execute(download);
    
            }
    
            //让线程执行完自动关闭
            threadPool.shutdown();
            System.err.println("分配线程 任务结束");
        }
    
    
        /**
         * 获取文件的大小 （单位 byte）
         *
         * @param urlLocation
         * @return
         * @throws IOException
         */
        private static long getContentLength(String urlLocation) throws IOException {
        
            URL url = null;
            if (urlLocation != null) {
        
                url = new URL(urlLocation);
            }
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            long len = conn.getContentLength();
    
            return len;
        }
    
    
        public static void main(String[] args) {
        
            try {
        
    
                //多个文件多线程下载  用逗号(,) 隔开
                String url = "http://img.tupianzj.com/uploads/allimg/140716/3-140G61501440-L.jpg, http://img.tupianzj.com/uploads/allimg/140418/3-14041Q43F40-L.jpg, http://img.tupianzj.com/uploads/allimg/140319/4-1403191055450-L.jpg, http://img.tupianzj.com/uploads/allimg/131120/3-1311200954320-L.jpg, http://img.tupianzj.com/uploads/allimg/130802/4-130P21036010-L.jpg, http://img.tupianzj.com/uploads/allimg/170107/9-1F10H004310-L.jpg, http://img.tupianzj.com/uploads/allimg/180523/9-1P5231000080-L.jpg, http://img.tupianzj.com/uploads/allimg/170309/9-1F3092145190-L.jpg, http://img.tupianzj.com/uploads/allimg/161107/9-16110H205210-L.jpg, http://img.tupianzj.com/uploads/allimg/170107/9-1F10H004310-L.jpg, http://img.tupianzj.com/uploads/allimg/140604/3-1406041414480-L.jpg, http://img.tupianzj.com/uploads/allimg/171017/9-1G01G15T00-L.jpg, http://img.tupianzj.com/uploads/allimg/170805/9-1FP51IA80-L.jpg, http://img.tupianzj.com/uploads/allimg/180331/9-1P3311131060-L.jpg, http://img.tupianzj.com/uploads/allimg/140102/3-1401021142510-L.jpg, http://img.tupianzj.com/uploads/allimg/161121/9-1611212039430-L.jpg, http://img.tupianzj.com/uploads/allimg/150317/7-15031G511460-L.jpg, http://img.tupianzj.com/uploads/allimg/180202/9-1P2021AS60-L.jpg, http://img.tupianzj.com/uploads/allimg/180202/9-1P2021A5070-L.jpg";
    
                MoreFileCreateThread createThread = new MoreFileCreateThread();
                // 网络文件url --- 存放路径 --- 创建的线程数
                createThread.getFileWithThreadPool(url, "D:/临时/threadimg/", 3);
    
            } catch (Exception e) {
        
                e.printStackTrace();
            }
        }
    
    
    }

--------------------

## 四、封装使用示例 ##

`接富文本提取资源上传`  
![在这里插入图片描述][1cd54625601b4792a71ee618cb93ac54.png]

[富文本提取资源][Link 1]

//将网络链接下载到本地,输出新的文件名
        @Transactional
        public String urlFileThread(String url, int poolLength) throws IOException {
        
    
            String fileName = (new SimpleDateFormat("yyyyMMddHHmmssSSS")).format(new Date()) + "_" + RandomUtil.randomInt(10000);
            String name = url.substring(url.lastIndexOf("/") + 1);
            int len = name.lastIndexOf(".");
            if (len <= 0) {
        
                throw new ServiceException("文件类型有误,请确认!");
            } else {
        
                fileName = fileName + name.substring(len);
            }
            CreateThread createThread = new CreateThread();
            // 网络文件url --- 存放路径 --- 创建的线程数
            createThread.getFileWithThreadPool(url, filePath + fileName, poolLength);
    
            return fileName;
        }

--------------------

[1cd54625601b4792a71ee618cb93ac54.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/03/23/ae82cefd95a243f8919c595035e623ee.png
[Link 1]: https://blog.csdn.net/weixin_45248225/article/details/130201021