java线程池怎么实现批量下载文件-乐山大橙子建站

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java线程池怎么实现批量下载文件

本篇内容主要讲解“java线程池怎么实现批量下载文件”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“java线程池怎么实现批量下载文件”吧!

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本文实例为大家分享了java线程池实现批量下载文件的具体代码，供大家参考，具体内容如下

1 创建线程池

package com.cheng.webb.thread;import java.util.concurrent.ArrayBlockingQueue;import java.util.concurrent.ExecutorService;import java.util.concurrent.ThreadFactory;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;import java.util.concurrent.atomic.AtomicInteger;public class ThreadUtil { /** * 创建批量下载线程池 * * @param threadSize 下载线程数 * @return ExecutorService */ public static ExecutorService buildDownloadBatchThreadPool(int threadSize) { int keepAlive = 0; String prefix = "download-batch"; ThreadFactory factory = ThreadUtil.buildThreadFactory(prefix); return new ThreadPoolExecutor(threadSize, threadSize, keepAlive, TimeUnit.SECONDS, new ArrayBlockingQueue<>(threadSize), factory); } /** * 创建自定义线程工厂 * * @param prefix 名称前缀 * @return ThreadFactory */ public static ThreadFactory buildThreadFactory(String prefix) { return new CustomThreadFactory(prefix); } /** * 自定义线程工厂 */ public static class CustomThreadFactory implements ThreadFactory { private String threadNamePrefix; private AtomicInteger counter = new AtomicInteger(1); /** * 自定义线程工厂 * * @param threadNamePrefix 工厂名称前缀 */ CustomThreadFactory(String threadNamePrefix) { this.threadNamePrefix = threadNamePrefix; } @Override public Thread newThread(Runnable r) { String threadName = threadNamePrefix + "-t" + counter.getAndIncrement(); return new Thread(r, threadName); } }}

2 批量下载文件

package com.cheng.webb.thread;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.io.File;import java.io.FileOutputStream;import java.io.InputStream;import java.net.HttpURLConnection;import java.net.URL;import java.util.ArrayList;import java.util.List;import java.util.Map;import java.util.concurrent.*;/** * 文件下载类 * * @author shucheng * @creation 2019年1月30日下午4:41:32 */public class DownloadUtil { private static Logger logger = LoggerFactory.getLogger(DownloadUtil.class); /** * 下载线程数 */ private static final int DOWNLOAD_THREAD_NUM = 14; /** * 下载线程池 */ private static ExecutorService downloadExecutorService = ThreadUtil .buildDownloadBatchThreadPool(DOWNLOAD_THREAD_NUM); /** * 文件下载 * * @param fileUrl * 文件url,如:https://img3.doubanio.com//view//photo//s_ratio_poster//public//p2369390663.webp * @param path * 存放路径,如: /opt/img/douban/my.webp */ public static void download(String fileUrl, String path) { // 判断存储文件夹是否已经存在或者创建成功 if (!createFolderIfNotExists(path)) { logger.error("We can't create folder:{}", getFolder(path)); return; } InputStream in = null; FileOutputStream out = null; try { URL url = new URL(fileUrl); HttpURLConnection conn = (HttpURLConnection) url.openConnection(); conn.setRequestMethod("GET"); // 2s conn.setConnectTimeout(10000); in = conn.getInputStream(); out = new FileOutputStream(path); int len; byte[] arr = new byte[1024 * 1000]; while (-1 != (len = in.read(arr))) { out.write(arr, 0, len); } out.flush(); conn.disconnect(); } catch (Exception e) { logger.error("Fail to download: {} by {}", fileUrl, e.getMessage()); } finally { try { if (null != out) { out.close(); } if (null != in) { in.close(); } } catch (Exception e) { // do nothing } } } /** * 创建文件夹,如果文件夹已经存在或者创建成功返回true * * @param path * 路径 * @return boolean */ private static boolean createFolderIfNotExists(String path) { String folderName = getFolder(path); if (folderName.equals(path)) { return true; } File folder = new File(getFolder(path)); if (!folder.exists()) { synchronized (DownloadUtil.class) { if (!folder.exists()) { return folder.mkdirs(); } } } return true; } /** * 获取文件夹 * * @param path * 文件路径 * @return String */ private static String getFolder(String path) { int index = path.lastIndexOf("/"); return -1 != index ? path.substring(0, index) : path; } /** * 下载资源 *

* issue: 线程池创建过多 *

* 最大批量下载为5,请知悉 * * @param resourceMap * 资源map, key为资源下载url,value为资源存储位置 */ public static void batch(Map resourceMap) { if (resourceMap == null || resourceMap.isEmpty()) { return; } try { List keys = new ArrayList<>(resourceMap.keySet()); int size = keys.size(); int pageNum = getPageNum(size); for (int index = 0; index < pageNum; index++) { int start = index * DOWNLOAD_THREAD_NUM; int last = getLastNum(size, start + DOWNLOAD_THREAD_NUM); final CountDownLatch latch = new CountDownLatch(last - start); // 获取列表子集 List urlList = keys.subList(start, last); for (String url : urlList) { // 提交任务 Runnable task = new DownloadWorker(latch, url, resourceMap.get(url)); downloadExecutorService.submit(task); } latch.await(); } } catch (Exception e) { logger.error("{}", e); } logger.info("Download resource map is all done"); } /** * 获取最后一个元素 * * @param size * 列表长度 * @param index * 下标 * @return int */ private static int getLastNum(int size, int index) { return index > size ? size : index; } /** * 获取划分页面数量 * * @param size * 列表长度 * @return int */ private static int getPageNum(int size) { int tmp = size / DOWNLOAD_THREAD_NUM; return size % DOWNLOAD_THREAD_NUM == 0 ? tmp : tmp + 1; } /** * 下载线程 */ static class DownloadWorker implements Runnable { private CountDownLatch latch; private String url; private String path; DownloadWorker(CountDownLatch latch, String url, String path) { this.latch = latch; this.url = url; this.path = path; } @Override public void run() { logger.debug("Start batch:[{}] into: [{}]", url, path); DownloadUtil.download(url, path); logger.debug("Download:[{}] into: [{}] is done", url, path); latch.countDown(); } }}

3 测试批量下载文件

package com.cheng.webb.thread;import java.util.HashMap;import java.util.Map;import org.junit.Test;import com.alibaba.fastjson.JSON;public class DownLoadTest { String json = "{\r\n" + " \"http://www.xxx.com/111/123.mp4\":\"myFile/111/123.mp4\",\r\n" + " \"http://www.xxx.com/111/124.mp4\":\"myFile/111/124.mp4\",\r\n" + " \"http://www.xxx.com/111/125.mp4\":\"myFile/111/125.mp4\"\r\n" + "}"; @SuppressWarnings("unchecked") @Test public void test() { Map map = new HashMap<>(); Map resMap = JSON.parseObject(json, map.getClass()); int times = 1; for (int index = 0; index < times; index++) { DownloadUtil.batch(resMap); } }}

到此，相信大家对“java线程池怎么实现批量下载文件”有了更深的了解，不妨来实际操作一番吧！这里是创新互联网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！

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