jsp页面动态生成验证码

该文章主要实现的功能是在jsp页面中动态显示验证码，点击验证码能够实现验证码的刷新。

验证码在前台显示的为一张图片，而该图片是通过后台Servlet生成的，原理为：用Graphics画出一张图片，输入BufferedImage图片缓冲区中，然后通过ImageIO流输出出来。前台标签为<img/>标签，img的src属性指向Servlet，并通过img标签的onclick事件调用Servlet，实现验证码图片的刷新。

点击刷新后:

jsp页面代码为：

<tr><td>验证码：</td><td><input type="text" name="validate" size="5" class="text" onBlur="checkCode()"/>   <img class="code" alt="点击刷新" src="code" onclick="this.src='code?s='+new Date().getTime();" ></td><td><div id="checkCode" class="check">*</div></td></tr>

CodeServlet代码为：

import java.awt.Color;import java.awt.Font;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.util.Random;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.ServletOutputStream;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * 生成验证码的类 * @author guduchina */@SuppressWarnings("serial")public class CodeServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {this.doPost(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("image/JPEG");ServletOutputStream out = response.getOutputStream();// 定义图片的高度和宽度int width = 80;int height = 25;// 定义随机数对象Random ran = new Random();// 定义图片缓冲区，使用RGB模式输出图片BufferedImage image = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);// 定义画笔工具对象Graphics graphics = image.getGraphics();// 设置验证码框的背景颜色graphics.setColor(new Color(200, 200, 200));// 填充整个矩形graphics.fillRect(0, 0, width, height);// 定义要显示的验证码StringBuffer sb = new StringBuffer("");// 定义验证码数组String[] code = { "A", "a", "B", "b", "C", "c", "D", "d", "E", "e","F", "f", "G", "g", "H", "h", "I", "i", "J", "j", "K", "k","L", "l", "M", "m", "N", "n", "O", "o", "P", "p", "Q", "q","R", "r", "S", "s", "T", "t", "U", "u", "V", "v", "W", "w","X", "x", "Y", "y", "Z", "z", "0", "1", "2", "3", "4", "5","6", "7", "8", "9", "0", "1", "2", "3", "4", "5", "6", "7","8", "9", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9","0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "1","2", "3", "4", "5", "6", "7", "8", "9", "0", "1" };for (int i = 0; i < 4; i++) {String str = code[ran.nextInt(code.length)];// 设置颜色graphics.setColor(new Color(ran.nextInt(150), ran.nextInt(150), ran.nextInt(150)));// 设置字体graphics.setFont(new Font("宋体", Font.BOLD, 20));// 绘制验证码graphics.drawString(str, 20 * i+4, 20 - ran.nextInt(5));sb.append(str);}// 随机产生100个干扰点for (int i = 0; i < 100; i++) {// 随机生成干扰点的坐标int x = ran.nextInt(width);int y = ran.nextInt(height);// 随机生成干扰点的颜色graphics.setColor(new Color(ran.nextInt(185) + 40,ran.nextInt(185) + 40, ran.nextInt(185) + 40));// 设置干扰点的位置长宽graphics.drawOval(x, y, 1, 1);}String codeInfo = sb.toString();// 将验证码的值放到session中，以供前台进行验证request.getSession().setAttribute("code", codeInfo);// 将Image通过out输出为jpeg格式的图片ImageIO.write(image, "JPEG", out);out.flush();out.close();}}

然后就是web.xml配置代码：

<servlet>    <servlet-name>CodeServlet</servlet-name>    <servlet-class>com.niit.cpw.servlet.CodeServlet</servlet-class>  </servlet><servlet-mapping>    <servlet-name>CodeServlet</servlet-name>    <url-pattern>/code</url-pattern>  </servlet-mapping>

这篇文章写的是生成验证码的，还有一篇文章写的是用jQuery+Ajax+Servlet进行验证验证码是否正确，有兴趣的朋友可以看看。