文件下载

@WebServlet("/download")
public class DowenloadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String fileName= req.getParameter("file");
        String name = req.getParameter("name");

        System.out.println(fileName);

        File saveDir = new File("D:/upload");
        File file = new File(saveDir,fileName);

        if(file.exists()){
            if(StringUtils.isNotEmpty(name)){
                //设置文件头 二进制文件代码为了让浏览器不识别 而弹窗
                resp.setContentType("application/octet-stream");

                //告诉浏览器下载文件大小，浏览器知道大小会在下载进度条上有区别
                //resp.setContentLengthLong(file.length());
                resp.setContentLength((int) file.length());

                //下载文件名为中文出现乱码 如下解决
                fileName = new String(fileName.getBytes("UTF-8"),"ISO8859-1");
                //设置下载的文件名
                resp.addHeader("Content-Disposition","attachment;filename=\""+fileName+"\"");
            }

            //响应输出流
            OutputStream outputStream = resp.getOutputStream();

            FileInputStream fileInputStream = new FileInputStream(file);

            IOUtils.copy(fileInputStream,outputStream);


            outputStream.flush();
            outputStream.close();
            fileInputStream.close();

        }else {
            resp.sendError(404,"文件未找到");
        }

    }
}