验证码（转载）

Java代码

<%@ page language="java" contentType="text/html; charset=GBK" pageEncoding="GBK"%>
<%
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + request.getContextPath() + "/";
%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<html>
<head>
<base href="<%=basePath%>">
<title>实训管理系统</title>
<link rel="stylesheet" type="text/css" href="css/team.css" />
<script type="text/javascript">
function changeValidateCode(obj) {
/***
* 获取当前的时间作为参数，无具体意义
* 每次请求需要一个不同的参数，否则可能会返回同样的验证码
* 这和浏览器的缓存机制有关系，也可以把页面设置为不缓存，这样就不用这个参数了。
*/
var timenow = new Date().getTime();
obj.src="LoginCode.servlet?d="+timenow;
}
</script>
</head>
<body>
<div id="top">
<h1>实训管理系统</h1>
</div>
<div id="content">
<form action="admin/Login" method="post">
<p>用  户：<input type="text" name="admin.name">
<p>密  码：<input type="password" name="admin.password">
<p>验证码：<input type="text" name="code" size="11"><img src="LoginCode.servlet" onclick="changeValidateCode(this)" title="点击图片刷新验证码"/>
<p><input type="submit" value="登录"><input type="reset" value="重置"/></p>
</form>
</div>
</body>
</html>

Java代码

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>training</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<filter>
<filter-name>LoginFilter</filter-name>
<filter-class>com.org.momo.filter.LoginFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>LoginFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<filter>
<filter-name>struts2</filter-name>
<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class>
</filter>
<filter-mapping>
<filter-name>struts2</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>LoginCodeServlet</servlet-name>
<servlet-class>com.org.momo.servlet.LoginCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginCodeServlet</servlet-name>
<url-pattern>/LoginCode.servlet</url-pattern>
</servlet-mapping>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>
</web-app>

Java代码

package com.org.momo.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.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginCodeServlet extends HttpServlet {
public LoginCodeServlet() {
super();
}
public void destroy() {
super.destroy();
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//设置输出类型和浏览器不保存缓存
response.setContentType("image/jpeg") ;
response.setHeader("Cache-Control", "no-cache") ;
//创建图片对象
int width = 60,height = 20 ;
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB) ;
Graphics g = image.getGraphics() ;
//生成随机数
Random random = new Random() ;
String s = "" ;
for(int i=0;i<4;i++){
s += random.nextInt(10) ;
}
//把随机数存到Session里面，便于等下比较
HttpSession session = request.getSession() ;
session.setAttribute("code",s) ;
//随机生成颜色 Color color = new Color(255,255,255) ; random.nextInt(256)的值范围是0~255
Color color = new Color(random.nextInt(256),random.nextInt(256),random.nextInt(256)) ;
//把随机数写到图片上
String a = null ;
Font font = new Font(a,Font.ITALIC,18) ;
g.setColor(color) ;
g.setFont(font);
g.drawString(s,10,height-5) ;
g.dispose() ; //关闭画笔
//把图片送到客户端
ServletOutputStream output = response.getOutputStream() ;
ImageIO.write(image,"JPEG",output) ;
output.flush(); //关闭输出流
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doGet(request,response) ;
}
public void init() throws ServletException {
}
}

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