@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    //1.要获取下载文件的路径
    //String realPath = this.getServletContext().getRealPath("/1.png");
    String realPath = "E:\\IntelliJ_Idea_workspaces\\JavaSE\\response\\src\\main\\resources\\图片.PNG";
    System.out.println("下载的文件的路径是:" + realPath);
    //2.要下载的文件是啥?
    String fileName = realPath.substring(realPath.lastIndexOf("\\") + 1);
    //3.设置想办法让浏览器能够支持(Content-Disposition)下载我们需要的东西,中文文件名URLEncoder.encode编码,否则有可能乱码.
    resp.setHeader("Content-Disposition", "attachment;fileName=" + URLEncoder.encode(fileName,"UTF-8"));
    //4.获取下载文件的输入流
    FileInputStream in = new FileInputStream(realPath);
    //5.创建缓冲区
    int len = 0;
    byte[] buffer = new byte[1024];
    //6.获取OutputStream
    ServletOutputStream out = resp.getOutputStream();
    //7.将FileOutputStream流写入到buffer缓冲区,使用OutputStream将缓冲区中的数据输入到客户端!
    while ((len = in.read(buffer)) > 0) {
        out.write(buffer, 0, len);
    }
    in.close();
    out.close();
}