以前看见各大网站都有图形化的验证码（虽然现在已经很少大型网站都不使用了）的时候就超级非常的好奇这个验证码到底是怎么实现的，真的是超级的羡慕…今天学习了很多东西，然后自己也来试着写了一下，为此记录下来，说不定以后会用得到吧 ~
这里以最原生的servlet来演示：
package com.service; import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.annotation.WebServlet; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.awt.*; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; //servlet3.0及以上可以使用注解， @WebServlet("/ValidateCodeServlet") public class ValidateCodeServlet extends HttpServlet { //这个地方其实数字1和字母l，还有数字0和字母0很多时候会混淆，可以去掉。 //字符数组用来生成验证码 private char[] codeSequence = {'A', '1', 'B', 'C', '2', 'D', '3', 'E', '4', 'F', '5', 'G', '6', 'H', '7', 'I', '8', 'J', 'K', '9', 'L', '1', 'M', '2', 'N', 'P', '3', 'Q', '4', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'}; @Override protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { int width = 76; int height = 45; Random random = new Random(); //设置response头信息 //禁止缓存 response.setHeader("Pragma", "No-cache"); response.setHeader("Cache-Control", "no-cache"); response.setDateHeader("Expires", 0); //生成缓冲区image类 BufferedImage image = new BufferedImage(width, height, 1); //产生image类的Graphics用于绘制操作 Graphics g = image.getGraphics(); //Graphics类的样式 背景颜色 g.setColor(new Color(16, 48, 77));//颜色可以随便改 g.setFont(new Font("Times New Roman", 0, 25)); g.fillRect(0, 0, width, height); //绘制干扰线 for (int i = 0; i < 20; i++) { g.setColor(this.getColor(130, 200)); int x = random.nextInt(width); int y = random.nextInt(height); int x1 = random.nextInt(12); int y1 = random.nextInt(12); g.drawLine(x, y, x + x1, y + y1); } //绘制字符 String strCode = ""; for (int i = 0; i < 4; i++) { String rand = String.valueOf(codeSequence[random.nextInt(codeSequence.length)]); strCode = strCode + rand; // g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110))); //设置字体颜色 g.setColor(new Color(255, 255, 255)); g.drawString(rand, 13 * i + 8, 30);//这里是所处图片的位置 } //将字符保存到session中用于前端的验证 request.getSession().setAttribute("authCode", strCode.toLowerCase()); g.dispose(); ImageIO.write(image, "JPEG", response.getOutputStream()); response.getOutputStream().flush(); } public Color getColor(int fc, int bc) { Random random = new Random(); if (fc > 255) fc = 255; if (bc > 255) bc = 255; int r = fc + random.nextInt(bc - fc); int g = fc + random.nextInt(bc - fc); int b = fc + random.nextInt(bc - fc); return new Color(r, g, b); } }servlet3.0以下代码需要在web.xml中加入下面的映射
<servlet> <servlet-name>ValidateCodeServlet</servlet-name> <servlet-class>com.service.ValidateCodeServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ValidateCodeServlet</servlet-name> <url-pattern>/ValidateCodeServlet</url-pattern> </servlet-mapping>最后来写个网页来演示一下：
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>验证码测试</title> </head> <body> <img src="/firstWeb/ValidateCodeServlet" /> </body> </html>刷新一下： 完美实现！！！
