文件下载&&动态生成验证码

蔚落 2022-06-08 11:10 172阅读 0赞

**文件下载**

> **下载方式（两头一流）：**  
> （1）超链接下载  
> `<a href="">下载</a>`  
> （2）编码下载 通过servlet完成  
> `<a href="/项目名称/servlet名称"？name=（文件名 ）>下载</a>`  
> a:设置文件的mime类型  
> `String mimeType=context.getMimeType(文件名)`  
> `response.setContentType(mimeType);`  
> b:设置下载头信息content-disposition  
> `response.setHeader("content-disposition","attachment;filename="+文件名称`  
> c:提供流

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // 获取下载文件名称
            String filename = request.getParameter("name");
            ServletContext context = this.getServletContext();
    
            // 文件下载
            // 1:设置文件的mime类型
            String mimeType = context.getMimeType(filename);
            response.setContentType(mimeType);
            // 2:设置下载的头信息
            response.setHeader("content-disposition", " attchment;filename=" + filename);
            // 3:对拷流
            // 获取输入流
            InputStream is = context.getResourceAsStream("/download/" + filename);
            // 获取输出流
            ServletOutputStream os = response.getOutputStream();
            int len = -1;
            byte[] b = new byte[1024];
            while ((len = is.read(b)) != -1) {
                os.write(b, 0, len);
            }
            os.close();
            is.close();
    
        }

> 用到的包：commons-io-1.4.jar,就可以不用流了

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // 获取下载文件名称
            String filename = request.getParameter("name");
            ServletContext context = this.getServletContext();
    
            // 文件下载
            // 1:设置文件的mime类型
            String mimeType = context.getMimeType(filename);
            response.setContentType(mimeType);
            // 2:设置下载的头信息
            response.setHeader("content-disposition", " attchment;filename=" + filename);
            // 3:对拷流
            // 获取输入流
            InputStream is = context.getResourceAsStream("/download/" + filename);
            // 获取输出流
            ServletOutputStream os = response.getOutputStream();
            // int len = -1;
            /* * byte[] b = new byte[1024]; while ((len = is.read(b)) != -1) { os.write(b, 0, len); } */
            IOUtils.copy(is, os);
            os.close();
            is.close();
    
        }

> **生成验证码**  
> 点击看不清可以换一张

/** * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response) */
        protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            // 使用java图形界面技术绘制一张图片
            int charNum = 4;
            int width = 30 * 4;
            int height = 30;
            // 1:创建一张内存图片
            BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
            // 2:获得绘制图像
            Graphics graphics = bufferedImage.getGraphics();
            // 3:绘制背颜色
            graphics.setColor(Color.YELLOW);
            graphics.fillRect(0, 0, width, height);
            // 4:绘制图片边框
            graphics.setColor(Color.BLUE);
            graphics.drawRect(0, 0, width - 1, height - 1);
            // 5:输出验证码内容
            graphics.setColor(Color.RED);
            graphics.setFont(new Font("宋体", Font.BOLD, 20));
            // 随机输出4个字符
            Graphics2D graphics2d = (Graphics2D) graphics;
            String s = "ABCDEFGHIJKLMNOPQRSTUVWXYZ23456789";
            Random random = new Random();
            // session中要用到
            String msg = "";
            int x = 5;
            for (int i = 0; i < 4; i++) {
                int index = random.nextInt(32);
                String content = String.valueOf(s.charAt(index));
                msg += content;
                double theta = random.nextInt(45) * Math.PI / 180;
                // 让字体扭曲
                graphics2d.rotate(theta, x, 18);
                graphics2d.drawString(content, x, 18);
                graphics2d.rotate(-theta, x, 18);
                x += 30;
            }
            // 6.绘制干扰线
            graphics.setColor(Color.GRAY);
            for (int i = 0; i < 5; i++) {
                int x1 = random.nextInt(width);
                int x2 = random.nextInt(width);
    
                int y1 = random.nextInt(height);
                int y2 = random.nextInt(width);
                graphics.drawLine(x1, y1, x2, y2);
            }
            // 释放资源
            graphics.dispose();
            // 图片输出ImageIO
            ImageIO.write(bufferedImage, "jpg", response.getOutputStream());
    
        }

**referer（盗链）**

// 获取 浏览器内核
            String agent = request.getHeader("user-agent");
            System.out.println(agent);
            // 获取referer
            String referer = request.getHeader("referer");
            if (referer == null) {
                System.out.println("直接在地址栏上输入的");
            } else if (referer.contains("92.168.")) {
                System.out.println("哥们姐妹点的");
            } else {
                System.out.println("盗链不好");
            }