动态生成验证码

package com.thinkbank.code;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
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 randomCode extends HttpServlet {
 
 private int width = 60;
 private int height = 30;
 

 protected void service(HttpServletRequest arg0, HttpServletResponse arg1)
 throws ServletException, IOException {
  BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
  Graphics2D g = image.createGraphics();
  //创建一个随即数生成器
  Random random = new Random();
  g.setColor(Color.WHITE);
  g.fillRect(0,0,width,height);
  
  //创建字体，字体的大小应该根据图片的高度来确定。
  Font font = new Font("Times New Roman",Font.PLAIN,18);
  //设置字体
  g.setFont(font);
  //画边框
  g.setColor(Color.BLACK);
  g.drawRect(0,0,width-1,height-1);
  //随即产生160条干扰线，使程序中的验证码不易被其他程序探测到
  g.setColor(Color.GRAY);
  for (int i=0;i<160;i++){
   int x = random.nextInt(width);
   int y = random.nextInt(height);
   int x1 = random.nextInt(12);
      int y1 = random.nextInt(12);
      g.drawLine(x,y,x+x1,y+y1);
  }
  //randomcode用于保存随即产生的验证码，以便于用户登陆后进行验证
  StringBuffer randomcode = new StringBuffer();
  int red = 0;
  int green = 0;
  int blue = 0;
  
  //随即产生4位数的验证码
  for (int i=0;i<4;i++){
   //得到随即产生的验证码数字
   String str = String.valueOf(random.nextInt(10));
   
   //产生随即的颜色分量来构造颜色值，这样输出的每位数字的颜色值都不相同
   red = random.nextInt(110);
   green = random.nextInt(50);
   blue = random.nextInt(50);
   
   //随即产生的颜色将验证码绘制到图象中
   g.setColor(new Color(red,green,blue));
   g.drawString(str,13*i+6,16);
   
   //将产生的4个随即数组合在一起
   randomcode.append(str);
  }
  //将四位数字的验证码保存到session中
  HttpSession session = arg0.getSession();
  session.setAttribute("randomcode",randomcode.toString());
  
  //禁止图象缓存
  arg1.setHeader("Pragma","no-cache");
  arg1.setHeader("Cache-Control","no-cache");
  arg1.setDateHeader("Expires",0);
  
  arg1.setContentType("image/jpeg");
  //将图象输出到servlet输出流中
  ServletOutputStream sos = arg1.getOutputStream();
  ImageIO.write(image,"jpeg",sos);
  sos.close();
  
 }
 public randomCode() {
  super();
 }
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
 }
 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

 }
}

 

 

package com.thinkbank.code;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class logincheck extends HttpServlet {

 /**
  * The doGet method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to get.
  *
  * @param request the request send by the client to the server
  * @param response the response send by the server to the client
  * @throws ServletException if an error occurred
  * @throws IOException if an error occurred
  */
 public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  response.setContentType("text/html");
 }

 /**
  * The doPost method of the servlet. <br>
  *
  * This method is called when a form has its tag value method equals to post.
  *
  * @param request the request send by the client to the server
  * @param response the response send by the server to the client
  * @throws ServletException if an error occurred
  * @throws IOException if an error occurred
  */
 public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {

  response.setContentType("text/html;charset=gbk");
  request.setCharacterEncoding("gbk");
  PrintWriter out = response.getWriter();
  HttpSession session = request.getSession();
  String randomCode = (String) session.getAttribute("randomcode");
  
  if (randomCode == null){
   response.sendRedirect("login.jsp");
   return ;
  }
  
  String reqRandom = request.getParameter("random");  
    
  if (randomCode.equals(reqRandom)){
   out.println("恭喜你，输入正确!");
  }else{
   out.println("输入错误，请返回重新输入!");
  }
  out.close();
 }

}

 

 

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
   
    <title>登陆页面</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="/RandomCodeServlet/logincheck" method="post">
      <table>
    <tr>
      <td>用户名:</td>
      <td><INPUT type="text" name="username"></td>
    </tr>
    <tr>
      <td>密  码:</td>
      <td><INPUT type="password" name="password"></td>
    </tr>
    <tr>
      <td>验证码:</td>
      <td><INPUT type="text" name="random" maxlength="4"><IMG src="randomCode"></td>
    </tr>
    <tr>
        <td><INPUT type="reset" value="重填"></td>
       <td><INPUT type="submit" value="提交"></td>
    </tr>
  </table>

    </FORM>
  </body>
</html>