JavaWeb-Response-下载文件以及实现验证码功能

飞熊 • 2023年6月20日下午5:10 • 后端笔记 • 阅读 231

文件下载：

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1. 获取下载文件的路径
        String filePath = "E:\\Java学习\\javaWeb02-servlet\\servlet03\\src\\main\\resources\\w02.jpg";
        //2. 下载的文件名称
        String fileName = filePath.substring(filePath.lastIndexOf("\\")+1);
        System.out.println("下载的文件名称为："+fileName);
        //3. 让浏览器支持我们需要下载的东西
        resp.setHeader("Content-disposition","attachment;filename"+ URLEncoder.encode(fileName,"UTF-8"));
        //4. 获取下载文件的输入流
        FileInputStream is = new FileInputStream(filePath);
        //5. 创建缓冲区
        int len = 0;
        byte[] bytes = new byte[1024];
        //6. 获取outputstream对象
        ServletOutputStream os = 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出到客户端
        len = is.read(bytes);
        while (len > 0){
            os.write(bytes,0,len);
        }

        is.close();
        os.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}

验证码功能

public class ImageServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.setHeader("refresh","3");//设置浏览器3s刷新
        //在内存中创建一个图片
        BufferedImage image = new BufferedImage(80, 20, BufferedImage.TYPE_INT_RGB);
        //得到图片
        Graphics2D g = (Graphics2D) image.getGraphics();
        //设置图片的背景颜色
        g.setBackground(Color.white);
        g.fillRect(0,0,80,20);
        //给图片写数据
        g.setColor(Color.blue);
        g.setFont(new Font(null,Font.BOLD,20));
        g.drawString(makeNums(),0,20);
        //告诉浏览器这个请求用图片的方式打开
        resp.setContentType("image/jpg");
        //清除缓存
        resp.setDateHeader("expires",-1);
        resp.setHeader("Cache-Control","no-cache");
        resp.setHeader("Pragma","no-cache");
        //把图片写给浏览器
        ImageIO.write(image,"jpg",resp.getOutputStream());
    }

	//定义一个方法实现生成随机6位数作为验证码
    private String makeNums(){
        Random random = new Random();
        String num = random.nextInt(999999) + "";
        StringBuffer bf = new StringBuffer();
        for (int i = 0; i < 6-num.length(); i++) {
            bf.append("0");
        }
        num = bf.toString()+num;
        return num;
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}