/**
   * 文件下载
   */
  public void downloadFile(HttpServletResponse response, BufferedInputStream bis, String fileName) {
    OutputStream os = null;
    BufferedOutputStream bos = null;
    try {
      //文件流的声明
      //重点突出(特别注意),通过response获取的输出流，作为服务端向客户端浏览器输出内容的通道
      os = response.getOutputStream();
      // 为了提高效率使用缓冲区流
      bos = new BufferedOutputStream(os);
      // 对文件名进行编码处理中文问题
      // 处理中文文件名的问题
      fileName = java.net.URLEncoder.encode(fileName, "UTF-8");
      // 处理中文文件名的问题
      fileName = new String(fileName.getBytes(StandardCharsets.UTF_8), "GBK");
      response.reset();
      response.setCharacterEncoding("UTF-8");
      // 不同类型的文件对应不同的MIME类型
      response.setContentType("application/x-msdownload");
      response.setHeader("Content-Disposition", "attachment;filename=" + fileName);
      int bytesRead;
      byte[] buffer = new byte[4096];
      //重点
      while ((bytesRead = bis.read(buffer)) != -1) {
        // 将文件发送到客户端
        bos.write(buffer, 0, bytesRead);
        bos.flush();
      }

    } catch (Exception ex) {
      throw new RuntimeException(ex);
    } finally {
      try {
        if (null != bis) {
          bis.close();
        }
        if (null != bos) {
          bos.close();
        }
        if (null != os) {
          os.close();
        }
      } catch (Exception ex) {
        System.out.println(ex.getMessage());
      }
    }
  }

生成临时文件方式下载

/**
   * 测试文件上传，需要生成本地文件
   */
  @RequestMapping(value = "/getZipFiles2",method =RequestMethod.GET)
  @ResponseBody
  public void getZipFiles2(HttpServletResponse response) throws Exception {
    // 获取三个文件的字符流
    File file1 = new File("D:\\test\\1.exe");
    File file2 = new File("D:\\test\\2.exe");
    File file3 = new File("D:\\test\\3.exe");
    BufferedInputStream bis1 = new BufferedInputStream(new FileInputStream(file1), 1024);
    BufferedInputStream bis2 = new BufferedInputStream(new FileInputStream(file2), 1024);
    BufferedInputStream bis3 = new BufferedInputStream(new FileInputStream(file3), 1024);
    List<BufferedInputStream> fileList = new ArrayList();
    fileList.add(bis1);
    fileList.add(bis2);
    fileList.add(bis3);
    //创建zip输出流
    ZipOutputStream out = new ZipOutputStream(new FileOutputStream("D:\\test\\1.zip"));
    //创建缓冲输出流
    BufferedOutputStream bos = new BufferedOutputStream(out);
    for (int i = 0; i < fileList.size(); i++) {
      out.putNextEntry(new ZipEntry(i+".exe"));
      int len=-1;
      //将源文件写入到zip文件中
      byte[] buf = new byte[1024];
      while ((len = fileList.get(i).read(buf)) != -1) {
        bos.write(buf,0,len);
      }
      fileList.get(i).close();
    }
    bos.close();
    // 输出流转输入流
    downloadFile(response, new BufferedInputStream(new FileInputStream("D:\\test\\1.zip"), 1024), "1.zip");
  }

测试

三个文件压缩后的大小大概是192MB，其实算比较大了。

我们看到总用时是8.83秒（博主多次测试，大概都是这个时间）。

web项目下载文件，总有人喜欢先在本地生成临时文件，在此验证其效率，看是否可以进一步优化_输出流

直接输出流转输入流的方式下载

/**
   * 测试文件上传，不需要生成本地文件
   */
  @RequestMapping(value = "/getZipFiles1",method =RequestMethod.GET)
  @ResponseBody
  public void getZipFiles1(HttpServletResponse response) throws Exception {
    // 获取三个文件的字符流
    File file1 = new File("D:\\test\\1.exe");
    File file2 = new File("D:\\test\\2.exe");
    File file3 = new File("D:\\test\\3.exe");
    BufferedInputStream bis1 = new BufferedInputStream(new FileInputStream(file1), 1024);
    BufferedInputStream bis2 = new BufferedInputStream(new FileInputStream(file2), 1024);
    BufferedInputStream bis3 = new BufferedInputStream(new FileInputStream(file3), 1024);
    List<BufferedInputStream> fileList = new ArrayList();
    fileList.add(bis1);
    fileList.add(bis2);
    fileList.add(bis3);
    // 压缩成一个zip
    //创建一个ByteArray输出流
    ByteArrayOutputStream arrayOutputStream =new ByteArrayOutputStream();
    //创建zip输出流
    ZipOutputStream out = new ZipOutputStream(arrayOutputStream);
    //创建缓冲输出流
    BufferedOutputStream bos = new BufferedOutputStream(out);
    for (int i = 0; i < fileList.size(); i++) {
      out.putNextEntry(new ZipEntry(i+".exe"));
      int len=-1;
      //将源文件写入到zip文件中
      byte[] buf = new byte[1024];
      while ((len = fileList.get(i).read(buf)) != -1) {
        bos.write(buf,0,len);
      }
      fileList.get(i).close();
    }
    bos.close();
    // 输出流转输入流
    InputStreamSource inputStreamSource = new ByteArrayResource(arrayOutputStream.toByteArray());
    downloadFile(response, new BufferedInputStream(inputStreamSource.getInputStream()), "1.zip");
  }