SPRINGBOOT 下载

SPRINGBOOT通过以下三种方式实现文件下载功能：
1. 通过URL连接下载网络文件到本地：

@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;
        fileOutputStream.write(buffer, 0, byteread);
    }
    fileOutputStream.close();
}

2. 将文件的输入流循环写入响应输出流，实现文件下载：

@RequestMapping("/downloadLocal")
public void downloadLocal(String path, HttpServletResponse response) throws IOException {
    InputStream inputStream = new FileInputStream(path);
    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;
    while ((len = inputStream.read(b)) > 0) {
        outputStream.write(b, 0, len);
    }
    inputStream.close();
}

3. 将网络文件获取到服务器后，经过服务器处理后响应给前端：

@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) {
        response.setHeader("Content-Disposition", "inline; filename=" + URLEncoder.encode(filename, "UTF-8"));
    } else {
        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();
}