java验证码实例

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1.servlet, ImageServlet.java

package com.bc.servlet; 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.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ImageServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } // 生成数字和字母的验证码 public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { BufferedImage img = new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB); // 得到该图片的绘图对象 Graphics g = img.getGraphics(); Random r = new Random(); Color c = new Color(200, 150, 255); g.setColor(c); // 填充整个图片的颜色 g.fillRect(0, 0, 68, 22); // 向图片中输出数字和字母 StringBuffer sb = new StringBuffer(); char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray(); int index, len = ch.length; for (int i = 0; i < 4; i ++) { index = r.nextInt(len); g.setColor(new Color(r.nextInt(88), r.nextInt(188), r.nextInt(255))); g.setFont(new Font("Arial", Font.BOLD | Font.ITALIC, 22));// 输出的字体和大小 g.drawString("" + ch[index], (i * 15) + 3, 18);//写什么数字，在图片的什么位置画 sb.append(ch[index]); } request.getSession().setAttribute("piccode", sb.toString()); ImageIO.write(img, "JPG", response.getOutputStream()); } }

2.web.xml配置servlet

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee

http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

<servlet-name>ImageServlet</servlet-name>

<servlet-class>com.bc.servlet.ImageServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>ImageServlet</servlet-name>

<url-pattern>/servlet/ImageServlet</url-pattern>

</servlet-mapping>

</web-app>

3.AdminLogin.jsp调用