Purpose:
Prevent malicious form registration
Generate verification code image
1. Define width and height
int width = 100; int height = 50;
2. Use BufferedImage to generate images in memory
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
3. Draw background and borders
Graphics g = image.getGraphics(); g.setColor(Color.WHITE); g.fillRect(0, 0, width, height); g.setColor(Color.BLACK); g.drawRect(0, 0, width - 1, height - 1);
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4. Create a random character set and random number object
//字符集 String str = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefgjijklmnopqrstuvwxyz"; //随机数 Random ran = new Random();
5. Create a random color generation method
private Color getRandomColor(Random random) { //获取随机颜色 int colorIndex = random.nextInt(3); switch (colorIndex) { case 0: return Color.BLUE; case 1: return Color.GREEN; case 2: return Color.RED; case 3: return Color.YELLOW; default: return Color.MAGENTA; } }
6. Draw Verification code characters
//绘制验证码 for (int i = 0; i < 4; i++) { //获取随机字符 int index = ran.nextInt(str.length()); char ch = str.charAt(index); //获取随机色 Color randomColor = getRandomColor(ran); g.setColor(randomColor); //设置字体 Font font = new Font("宋体", Font.BOLD, height / 2); g.setFont(font); //写入验证码 g.drawString(ch + "", (i == 0) ? width / 4 * i + 2 : width / 4 * i, height - height / 4); }
7, draw interference lines
//干扰线 for (int i = 0; i < 10; i++) { int x1 = ran.nextInt(width); int x2 = ran.nextInt(width); int y1 = ran.nextInt(height); int y2 = ran.nextInt(height); Color randomColor = getRandomColor(ran); g.setColor(randomColor); g.drawLine(x1, x2, y1, y2); }
8, use ImageIO to output pictures
ImageIO.write(image, "jpg", resp.getOutputStream());
to achieve refresh effect
1. Create a new html page
2. Use the img tag to display images
看不清，换一张
3. Use js to achieve the refresh effect
//点击图片时 var img = document.getElementById("//m.sbmmt.com/m/faq/identcode"); img.onclick = function (){ refesh(); } //点击连接时 var a = document.getElementById("refesh"); a.onclick = function (){ refesh(); //返回false防止a标签默认href行为 return false; } function refesh() { /** * 由于路径相同时浏览器会自动调用缓存中的图片 * 所以在连接后加时间戳解决此问题 */ var date = new Date().getTime(); img.src = "identcode?" + date; }
Finally Rendering:
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