通过response生成验证码 java验证码

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通过response生成验证码
验证码:
作用:防止暴力攻击
点击换一张的js代码:
function changeImg(obj){
//操作src属性
obj.src="/test/code?i="+Math.random();

}

代码参考：

public class CodeServlet extends HttpServlet {public 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.获得绘图对象Graphics graphics = bufferedImage.getGraphics();// 3、绘制背景颜色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 = "ABCDEFGHGKLMNPQRSTUVWXYZ23456789";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(height);graphics.drawLine(x1, y1, x2, y2);}// 释放资源graphics.dispose();// 图片输出 ImageIOImageIO.write(bufferedImage, "jpg", response.getOutputStream());}public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {}}

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