文件下载&&动态生成验证码

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");        }