近期基于項目上使用到的RestTemplate下載文件流，遇到1G以上的大文件，下載需要3-4分鐘，因為調用API接口沒有做分片與多線程， 文件流全部采用同步方式加載，性能很慢。最近結合網上案例及自己總結，寫了一個分片下載tuling/fileServer項目： 1.包含同步下載文件流在瀏覽器加載輸出相關代碼； 2.包含分片多線程下載分片文件及合并文件相關代碼；
另外在DownloadThread項目中使用代碼完成了一個遠程RestUrl請求去獲取一個遠端資源大文件進行多線程分片下載 到本地的一個案例，可以下載一些諸如.mp4/.avi等視頻類大文件。相關代碼也一并打包上傳。
同步下載，支持分片下載Range主要代碼：
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@Controllerpublic class DownLoadController { private static final String UTF8 = "UTF-8"; @RequestMapping("/download") public void downLoadFile(HttpServletRequest request, HttpServletResponse response) throws IOException { File file = new File("D:\\DevTools\\ideaIU-2021.1.3.exe"); response.setCharacterEncoding(UTF8); InputStream is = null; OutputStream os = null; try { // 分片下載 Range表示方式 bytes=100-1000 100- long fSize = file.length(); response.setContentType("application/x-download"); String fileName = URLEncoder.encode(file.getName(), UTF8); response.addHeader("Content-Disposition", "attachment;filename=" + fileName); // 支持分片下載 response.setHeader("Accept-Range", "bytes"); response.setHeader("fSize", String.valueOf(fSize)); response.setHeader("fName", fileName); long pos = 0, last = fSize - 1, sum = 0; if (null != request.getHeader("Range")) { response.setStatus(HttpServletResponse.SC_PARTIAL_CONTENT); String numberRange = request.getHeader("Range").replaceAll("bytes=", ""); String[] strRange = numberRange.split("-"); if (strRange.length == 2) { pos = Long.parseLong(strRange[0].trim()); last = Long.parseLong(strRange[1].trim()); if (last > fSize-1) { last = fSize - 1; } } else { pos = Long.parseLong(numberRange.replaceAll("-", "").trim()); } } long rangeLength = last - pos + 1; String contentRange = new StringBuffer("bytes").append(pos).append("-").append(last).append("/").append(fSize).toString(); response.setHeader("Content-Range", contentRange); response.setHeader("Content-Length", String.valueOf(rangeLength)); os = new BufferedOutputStream(response.getOutputStream()); is = new BufferedInputStream(new FileInputStream(file)); is.skip(pos); byte[] buffer = new byte[1024]; int length = 0; while (sum < rangeLength) { int readLength = (int) (rangeLength - sum); length = is.read(buffer, 0, (rangeLength - sum) <= buffer.length ? readLength : buffer.length); sum += length; os.write(buffer,0, length); } System.out.println("下載完成"); }finally { if (is != null){ is.close(); } if (os != null){ os.close(); } } }} |
多線程分片下載分片文件，下載完成之后合并分片主要代碼：
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@RestControllerpublic class DownloadClient { private static final Logger LOGGER = LoggerFactory.getLogger(DownloadClient.class); private final static long PER_PAGE = 1024L * 1024L * 50L; private final static String DOWN_PATH = "F:\\fileItem"; ExecutorService taskExecutor = Executors.newFixedThreadPool(10); @RequestMapping("/downloadFile") public String downloadFile() { // 探測下載 FileInfo fileInfo = download(0, 10, -1, null); if (fileInfo != null) { long pages = fileInfo.fSize / PER_PAGE; for (long i = 0; i <= pages; i++) { Future<FileInfo> future = taskExecutor.submit(new DownloadThread(i * PER_PAGE, (i + 1) * PER_PAGE - 1, i, fileInfo.fName)); if (!future.isCancelled()) { try { fileInfo = future.get(); } catch (InterruptedException | ExecutionException e) { e.printStackTrace(); } } } return System.getProperty("user.home") + "\\Downloads\\" + fileInfo.fName; } return null; } class FileInfo { long fSize; String fName; public FileInfo(long fSize, String fName) { this.fSize = fSize; this.fName = fName; } } /** * 根據開始位置/結束位置 * 分片下載文件，臨時存儲文件分片 * 文件大小=結束位置-開始位置 * * @return */ private FileInfo download(long start, long end, long page, String fName) { File dir = new File(DOWN_PATH); if (!dir.exists()) { dir.mkdirs(); } // 斷點下載 File file = new File(DOWN_PATH, page + "-" + fName); if (file.exists() && page != -1 && file.length() == PER_PAGE) { return null; } try { HttpClient client = HttpClients.createDefault(); HttpGet httpGet = new HttpGet("http://127.0.0.1:8080/download"); httpGet.setHeader("Range", "bytes=" + start + "-" + end); HttpResponse response = client.execute(httpGet); String fSize = response.getFirstHeader("fSize").getValue(); fName = URLDecoder.decode(response.getFirstHeader("fName").getValue(), "UTF-8"); HttpEntity entity = response.getEntity(); InputStream is = entity.getContent(); FileOutputStream fos = new FileOutputStream(file); byte[] buffer = new byte[1024]; int ch; while ((ch = is.read(buffer)) != -1) { fos.write(buffer, 0, ch); } is.close(); fos.flush(); fos.close(); // 最后一個分片 if (end - Long.parseLong(fSize) > 0) { // 開始合并文件 mergeFile(fName, page); } return new FileInfo(Long.parseLong(fSize), fName); } catch (IOException e) { e.printStackTrace(); } return null; } private void mergeFile(String fName, long page) { File file = new File(DOWN_PATH, fName); try { BufferedOutputStream os = new BufferedOutputStream(new FileOutputStream(file)); for (long i = 0; i <= page; i++) { File tempFile = new File(DOWN_PATH, i + "-" + fName); while (!file.exists() || (i != page && tempFile.length() < PER_PAGE)) { try { Thread.sleep(100); } catch (InterruptedException e) { e.printStackTrace(); } } byte[] bytes = FileUtils.readFileToByteArray(tempFile); os.write(bytes); os.flush(); tempFile.delete(); } File testFile = new File(DOWN_PATH, -1 + "-null"); testFile.delete(); os.flush(); os.close(); } catch (IOException e) { e.printStackTrace(); } } /** * 獲取遠程文件尺寸 */ private long getRemoteFileSize(String remoteFileUrl) throws IOException { long fileSize = 0; HttpURLConnection httpConnection = (HttpURLConnection) new URL(remoteFileUrl).openConnection(); //使用HEAD方法 httpConnection.setRequestMethod("HEAD"); int responseCode = httpConnection.getResponseCode(); if (responseCode >= 400) { LOGGER.debug("Web服務器響應錯誤!"); return 0; } String sHeader; for (int i = 1;; i++) { sHeader = httpConnection.getHeaderFieldKey(i); if (sHeader != null && sHeader.equals("Content-Length")) { LOGGER.debug("文件大小ContentLength:" + httpConnection.getContentLength()); fileSize = Long.parseLong(httpConnection.getHeaderField(sHeader)); break; } } return fileSize; } class DownloadThread implements Callable<FileInfo> { long start; long end; long page; String fName; public DownloadThread(long start, long end, long page, String fName) { this.start = start; this.end = end; this.page = page; this.fName = fName; } @Override public FileInfo call() { return download(start, end, page, fName); } }} |
代碼都在本地親測（已修復Bug）可用，目前比較欠缺的是沒有實現在分片下載時對應瀏覽器進行下載展示，需要暫存在本地磁盤目錄。 目前將代碼開源，希望能有更好解決方案的Coder Fork支持！也歡迎Star捧場。
博文參考了圖靈學院相關的分片下載案例教程，并修改了部分代碼實現：
WebUploader--基于SpringBoot搭建，Java文件上傳下載高階實戰
本文代碼已上傳至GitHub：
到此這篇關于SpringBoot大文件RestTemplate下載解決方案的文章就介紹到這了,更多相關SpringBoot RestTemplate下載內容請搜索服務器之家以前的文章或繼續瀏覽下面的相關文章希望大家以后多多支持服務器之家！
原文鏈接：https://www.cnblogs.com/yif0118/p/15456666.html
