java验证码程序

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一个简单的4位纯数字验证码程序：

登录界面login.jsp

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>        <title>登录验证码</title><meta http-equiv="pragma" content="no-cache"><meta http-equiv="cache-control" content="no-cache"><meta http-equiv="expires" content="0">    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3"><meta http-equiv="description" content="This is my page"><!--<link rel="stylesheet" type="text/css" href="styles.css">-->  </head>    <body>    <form action="${pageContext.request.contextPath}/servlet/LoginServlet" method="post">    用户名：<input type="text" name="username"/><br/>    密 码：<input type="password" name="password"/><br>    验证码：<input type="text" name="captcha" size="4"/><img  src="${pageContext.request.contextPath}/servlet/CaptchaServlet" width="120" height="25"/><br><input type="submit" value="登录"/>    </form>  </body></html>

CaptchaServlet.java

package cn.itcast.web.controller;import java.awt.Color;import java.awt.Font;import java.awt.GradientPaint;import java.awt.Graphics;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.PrintWriter;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;//输出验证码图像public class CaptchaServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {int width = 120;int height = 25;//对象，代表内存中的图片，BufferedImageBufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);//构建一副内存图像//画笔，花图像Graphics g = image.getGraphics();//图像上的画笔//1、设置颜色，画一个边线g.setColor(Color.GREEN);g.drawRect(0, 0, width, height);//2、设置颜色，填充色g.setColor(Color.YELLOW);g.fillRect(1, 1, width-2, height-2);//3、画干扰线g.setColor(Color.GRAY);Random r = new Random();for (int i = 0; i < 9; i++) {g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height));}//4、随机验证码g.setColor(Color.RED);g.setFont(new Font("宋体",Font.BOLD|Font.ITALIC,15));int x = 20;for (int i = 0; i < 4; i++) {String num = r.nextInt(10)+"";g.drawString(num, x, 20);x+=20;}System.out.println();//输出到页面上：response的响应输出液，字节液ImageIO.write(image, "jpg", response.getOutputStream());}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

配置文件：web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app version="3.0"    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_3_0.xsd">  <servlet>    <servlet-name>CaptchaServlet</servlet-name>    <servlet-class>cn.itcast.web.controller.CaptchaServlet</servlet-class>  </servlet>  <servlet-mapping>    <servlet-name>CaptchaServlet</servlet-name>    <url-pattern>/servlet/CaptchaServlet</url-pattern>  </servlet-mapping></web-app>

如果用ValidateCode.jar包，则：

CaptchaServlet.java

package cn.itcast.web.controller;import java.io.IOException;import javax.imageio.ImageIO;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import cn.dsna.util.images.ValidateCode;//输出验证码图像public class CaptchaServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//宽度、高度、验证码数、干扰线数ValidateCode vc = new ValidateCode(120, 25, 4, 9);String code = vc.getCode();System.out.println(code);//把验证码存放到HttpSession中request.getSession().setAttribute("code", code);//用字节流输出对应的图片ImageIO.write(vc.getBuffImg(), "jpg", response.getOutputStream());}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

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