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登陆验证码(Servlet实现)

servlet 登陆验证码 
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登陆验证码(Servlet实现)


1.前台登陆界面：
<%@ 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&nbsp;&nbsp;户：<input type="text" name="admin.name">
<p>密&nbsp;&nbsp;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>


2.web.xml配置文件配置servlet映射路径： 
<?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>



3.LoginCodeServlet.java处理类 
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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