java验证码实例

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>

  <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

<script language="javascript" >

	 // 重载验证码

    function reloadVerifyCode(){
    
           var timenow = new Date().getTime();                       

           document.getElementById("safecode").src="<%=request.getContextPath()%>/servlet/ImageServlet?d="+timenow;

    } 
</script>

<td> 
<img alt="验证码" id="safecode" src="<%=request.getContextPath()%>/servlet/ImageServlet"/>
              	<a href="javascript:reloadVerifyCode();"><br/>看不清楚,换一个</a>
              </td>