Java绘制验证码完整demo

----1，引入servlet的jar包，搭建好开发环境(eclipse+JDK等)

----2，编写主页面(输入用户、密码、验证码的页面index_demo_10.jsp)

<%@page import="com.util.JSPUtils"%>
<%@page import="java.util.ArrayList"%>
<%@page import="java.util.List"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>在提交表单时加入验证码</title>
   <%
       Integer count =0;
       Integer app_count =(Integer)application.getAttribute("app_count");//获取application中保存的记录数
       if(app_count==null || app_count<=0){
           ++count;
       }else{
           count=app_count+1;
       }

       application.setAttribute("app_count", count);
   %>
   <script type="text/javascript">
       function reloadCode(){
           var time=new Date();
           //这里定义时间参数是为了让浏览器认为这是一个新的请求，清空之前的缓存信息
           document.getElementById("safecode").src="<%=request.getContextPath()%>/servlet/ImageServlet?d="+time;
       }
       function validate(obj){
           var username=document.getElementById("username").value;
           var password=document.getElementById("password").value;
           if(username=='zhihao' && password=='123456'){
               document.form1.submit();
           }else{
               alert("您输入的账号或密码不对！");
               return;
           }
       }

   </script>
</head>
<body>
   <form name="form1" action="index_demo_11.jsp">
       
       <table>
           <tr>
               <td>用 户 名 :</td>
               <td><div id="onMouse"><input type="text" name="username" id="username" value="" onMouseOver="this.style.background='red';" onMouseOut="this.style.background='';"></div></td>
           </tr>
           <tr>
               <td>密 码  :</td>
               <td><input type="password" name="password" value="" id="password" onMouseOver="this.style.background='blue';" onMouseOut="this.style.background='';"></td>
           </tr>
           <tr>
               <td valign="bottom">验 证 码 :</td>
               <td>
                   <input type="text" name="yanzhengma" value="" onMouseOver="this.style.background='green';" onMouseOut="this.style.background='';" size="6" onblur="checkValidate();">
                   <img alt="验证码" src="<%=request.getContextPath()%>/servlet/ImageServlet" id="safecode" width="100" height="30" onclick="reloadCode()">
                   <a href="javascript:reloadCode()">看不清楚</a>
                   <span id="result"></span>
               </td>
           </tr>
           <tr>
               <td colspan="2"><input type="button" name="button" value="登录" onclick="validate(this);"></td>
           </tr>
       </table>
   </form>

</body>

</html>

--------3，配置web.xml，将对应的servlet配置进去

<?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" 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>JSP_demo2</display-name>
<welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
</welcome-file-list>


<context-param>
       <param-name>driver</param-name>
       <param-value>com.mysql.jdbc.Driver</param-value>
</context-param>
<context-param>
       <param-name>url</param-name>
       <param-value>jdbc:mysql://localhost:3306/proposal_info</param-value>
</context-param>
<context-param>
       <param-name>username</param-name>
       <param-value>root</param-value>
</context-param>
<context-param>
       <param-name>password</param-name>
       <param-value>b812w925</param-value>
</context-param>

<servlet>
   <servlet-name>imageServlet</servlet-name>
   <servlet-class>com.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
   <servlet-name>imageServlet</servlet-name>
   <url-pattern>/servlet/ImageServlet</url-pattern>
</servlet-mapping>
<servlet>
   <servlet-name>ValidateServlet</servlet-name>
   <servlet-class>com.servlet.ValidateServlet</servlet-class>
</servlet>
<servlet-mapping>
   <servlet-name>ValidateServlet</servlet-name>
   <url-pattern>/servlet/ValidateServlet</url-pattern>
</servlet-mapping>
</web-app>

----------4，编写后台ImageServlet，用来生成验证码图片并将该图片传到前端指定位置

package com.servlet;

import java.awt.image.RenderedImage;
import java.io.IOException;
import java.util.List;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.util.JSPUtils;

public class ImageServlet extends HttpServlet{
   @Override
   protected void service(HttpServletRequest req, HttpServletResponse res) throws ServletException, IOException {
       //获取验证码
       List<Object> list=JSPUtils.getYanZhengMa();
       req.getSession().setAttribute("piccode", list.get(0));
       ImageIO.write((RenderedImage)list.get(1),"jpg",res.getOutputStream());//用ImageIO将图片输出到页面
   }

}

---------5，编写具体实现绘制验证码图片JSPUtils

package com.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class JSPUtils {
   public static final String[] DATAS=new String[]{"0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
   public static final int SIX=4;
   public static final int WIDTH=65;//验证码图片的宽
   public static final int HEIGHT=25;//验证码图片的高
   //定义验证码的背景颜色
   public static final int BK_COLOR1=200;
   public static final int BK_COLOR2=200;
   public static final int BK_COLOR3=255;
   //创建一个方法用来生成随机验证码，6位数字与字母混合体(0-9+a-z)
   public static List<Object> getYanZhengMa(){
       List<Object> list=new ArrayList<Object>();
       /**
       * 1,使用BufferedImage对象对指定图片进行宽高透明度等设置
       * 2，获得Graphics对象
       * 3，使用Random获得随机数
       * 4，使用Graphics绘制图像
       * 5，记录验证码信息到session中
       * 6，使用ImageIO输出图片
       */
       BufferedImage buImage=new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_BGR);//Type_int_Rgb表示一个图像具有合成整数像素的8位RGB颜色分量
       Graphics graphics=buImage.getGraphics();
       Color co=new Color(BK_COLOR1,BK_COLOR2,BK_COLOR3);//验证码的背景图片
       graphics.setColor(co);
       graphics.fillRect(0,0,WIDTH,HEIGHT);//绘制图片的边框
       StringBuffer sb=new StringBuffer();//定义保存验证码字符串
       //创建一个1-35数字的随机数数组，然后从中进行随机取数
       String result="";
       Random random=new Random();
       for(int i=0;i<SIX;i++){
           int count=random.nextInt(DATAS.length);
           graphics.setColor(new Color(random.nextInt(250),random.nextInt(250),random.nextInt(250)));//为验证码字符串定义字体颜色
           graphics.setFont(new Font("宋体", Font.PLAIN, 24));//设置字体样式及大小
           graphics.drawString(DATAS[count],15*i+3,18);//画出字符
           sb.append(DATAS[count]);
       }
       //将得到的字符串及图片放入list中返回
       list.add(sb);
       list.add(buImage);
       return list;
   }

   public static void main(String[] args) {
       System.out.println("结果为："+getYanZhengMa());
   }
}

-----------------6,编写跳转页面index_demo_11.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>登陆成功页面</title>
</head>
<body>
   欢迎<%=request.getParameter("username") %>来到此界面，您是第<%=application.getAttribute("app_count") %>用户<br>
   客户信息：<br>
   用户名:<%=request.getParameter("username")%>,密码：<%=request.getParameter("password") %>
</body>
</html>

Java绘制验证码完整demo

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