1. 將文件以流的形式一次性讀取到內存,通過響應輸出流輸出到前端
/** * @param path 想要下載的文件的路徑 * @param response * @功能描述 下載文件: */ @RequestMapping("/download") public void download(String path, HttpServletResponse response) { try { // path是指想要下載的文件的路徑 File file = new File(path); log.info(file.getPath()); // 獲取文件名 String filename = file.getName(); // 獲取文件後綴名 String ext = filename.substring(filename.lastIndexOf(".") + 1).toLowerCase(); log.info("文件後綴名:" + ext); // 將文件寫入輸入流 FileInputStream fileInputStream = new FileInputStream(file); InputStream fis = new BufferedInputStream(fileInputStream); byte[] buffer = new byte[fis.available()]; fis.read(buffer); fis.close(); // 清空response response.reset(); // 設置response的Header response.setCharacterEncoding("UTF-8"); //Content-Disposition的作用:告知瀏覽器以何種方式顯示響應返回的文件,用瀏覽器打開還是以附件的形式下載到本地保存 //attachment表示以附件方式下載 inline表示在線打開 "Content-Disposition: inline; filename=文件名.mp3" // filename表示文件的默認名稱,因爲網絡傳輸只支持URL編碼的相關支付,因此需要將文件名URL編碼後進行傳輸,前端收到後需要反編碼才能獲取到真正的名稱 response.addHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(filename, "UTF-8")); // 告知瀏覽器文件的大小 response.addHeader("Content-Length", "" + file.length()); OutputStream outputStream = new BufferedOutputStream(response.getOutputStream()); response.setContentType("application/octet-stream"); outputStream.write(buffer); outputStream.flush(); } catch (IOException ex) { ex.printStackTrace(); } }
2、將輸入流中的數據循環寫入到響應輸出流中,而不是一次性讀取到內存,通過響應輸出流輸出到前端
/** * @param path 指想要下載的文件的路徑 * @param response * @功能描述 下載文件:將輸入流中的數據循環寫入到響應輸出流中,而不是一次性讀取到內存 */ @RequestMapping("/downloadLocal") public void downloadLocal(String path, HttpServletResponse response) throws IOException { // 讀到流中 InputStream inputStream = new FileInputStream(path);// 文件的存放路徑 response.reset(); response.setContentType("application/octet-stream"); String filename = new File(path).getName(); response.addHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(filename, "UTF-8")); ServletOutputStream outputStream = response.getOutputStream(); byte[] b = new byte[1024]; int len; //從輸入流中讀取一定數量的字節,並將其存儲在緩衝區字節數組中,讀到末尾返回-1 while ((len = inputStream.read(b)) > 0) { outputStream.write(b, 0, len); } inputStream.close(); }
3、下載網絡文件到本地
/** * @param path 下載後的文件路徑和名稱 * @param netAddress 文件所在網絡地址 * @功能描述 網絡文件下載到服務器本地 */ @RequestMapping("/netDownloadLocal") public void downloadNet(String netAddress, String path) throws IOException { URL url = new URL(netAddress); URLConnection conn = url.openConnection(); InputStream inputStream = conn.getInputStream(); FileOutputStream fileOutputStream = new FileOutputStream(path); int bytesum = 0; int byteread; byte[] buffer = new byte[1024]; while ((byteread = inputStream.read(buffer)) != -1) { bytesum += byteread; System.out.println(bytesum); fileOutputStream.write(buffer, 0, byteread); } fileOutputStream.close(); }
4.下載服務器文件到本地
package com.llp.response; import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.FileInputStream; import java.io.IOException; import java.net.URLEncoder; public class FileDownServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 1.獲取下載文件的路徑** String realPath="E:\\target\\classes\\ddl.txt"; System.out.println("下載文件路徑"+realPath); // 2.下載的文件名 String fileName=realPath.substring(realPath.lastIndexOf("\\"+1)); // 3.設置讓瀏覽器支持所下載的文件(設置中文編碼utf-8格式) resp.setHeader("Content-Disposition", "attachment;filename="+ URLEncoder.encode(fileName, "utf-8")); // 4.獲取下載文件的輸入流 FileInputStream in= new FileInputStream(realPath); // 5.創建緩衝區 int len=0; byte[] buffer=new byte[1024]; // 6.獲取OutputStream對象 ServletOutputStream out=resp.getOutputStream(); // 7.將FileOutputStream流寫入到buffer緩衝區 // 8.使用OutputStream將緩衝區中的數據輸入到客戶端 while((len=in.read(buffer))>0){ out.write(buffer,0,len); } in.close(); out.close(); } @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { super.doPost(req, resp); } }
5. 網絡文件獲取到服務器後,經服務器處理後響應給前端
/** * @param netAddress * @param filename * @param isOnLine * @param response * @功能描述 網絡文件獲取到服務器後,經服務器處理後響應給前端 */ @RequestMapping("/netDownLoadNet") public void netDownLoadNet(String netAddress, String filename, boolean isOnLine, HttpServletResponse response) throws Exception { URL url = new URL(netAddress); URLConnection conn = url.openConnection(); InputStream inputStream = conn.getInputStream(); response.reset(); response.setContentType(conn.getContentType()); if (isOnLine) { // 在線打開方式 文件名應該編碼成UTF-8 response.setHeader("Content-Disposition", "inline; filename=" + URLEncoder.encode(filename, "UTF-8")); } else { //純下載方式 文件名應該編碼成UTF-8 response.setHeader("Content-Disposition", "attachment; filename=" + URLEncoder.encode(filename, "UTF-8")); } byte[] buffer = new byte[1024]; int len; OutputStream outputStream = response.getOutputStream(); while ((len = inputStream.read(buffer)) > 0) { outputStream.write(buffer, 0, len); } inputStream.close(); }
參考:
https://blog.csdn.net/aaa58962458/article/details/120764754
https://blog.csdn.net/weixin_55491446/article/details/122951047