java验证码

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Java Servlet JavaScript QQ Cache

些篇以前写在QQ空间上，没什么人关注，还是转到这里跟大家分享

最近在网上找了一个验证码的代码，自己再改改，做点注释，留着自己以后用，拿出来分享
servlet
package chenlh;
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 ImageServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
public void doGet(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
            doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
   throws ServletException, IOException {
  int width=150;//验证码图片宽度
  int height=60;//验证码图片高度
  BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_3BYTE_BGR);
  Graphics g=image.getGraphics();
  Random random=new Random();//创建一个随机类
  g.setColor(getRandColor(200,250));//背景颜色要偏淡
  g.fillRect(0, 0, width, height);//画背景
  g.setColor(getRandColor(0,255));//边框颜色
        g.drawRect(0, 0, width-1, height-1);//画边框
  g.setColor(getRandColor(160,200));// 随机产生5条干扰线，使图象中的认证码不易被其它程序探测到
  for(int i=0;i<8;i++){
   int x=random.nextInt(width);
   int y=random.nextInt(height);
   int x1=random.nextInt(width);
   int y1=random.nextInt(height);
   g.drawLine(x, y, x1, y1);
  }
  g.setColor(getRandColor(160,200));// 随机产生100点，使图象中的认证码不易被其它程序探测到
  for(int i=0;i<100;i++){
   int x=random.nextInt(width);
   int y=random.nextInt(height);
   g.drawLine(x, y, x, y);
  }
        Font font = new Font("Times New Roman", Font.ITALIC,38);  // 创建字体，字体的大小应该根据图片的高度来定。
        g.setFont(font);//设置字体
        int length = 6;  // 设置默认生成4个验证码
  String s="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; // 设置备选验证码:包括"a-z"和数字"0-9"
  String sRand="";

        // 用随机产生的颜色将验证码绘制到图像中。
        // 生成随机颜色(因为是做前景，所以偏深)
        //调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
        g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
  for(int i=0;i<length;i++){
   String ch=String .valueOf(s.charAt(random.nextInt(s.length())));
   sRand+=ch;
   g.drawString(ch, 22*i+12, (random.nextInt(5)-2)*i+40);
  }
  //将生成的字符串存储在session中
  HttpSession session=request.getSession();
  session.setAttribute("checkCode", sRand);
  g.dispose();//图像生效
  //禁止图像缓存
  response.setHeader("Pragma", "No-cache");
  response.setHeader("Cache-Control", "no-cache");
  response.setDateHeader("Expires", 0);
  response.setContentType("image/jpeg");
  //创建二进制的输出流
  ServletOutputStream sos=response.getOutputStream();
        // 将图像输出到Servlet输出流中。
        ImageIO.write(image, "jpeg", sos);
        sos.flush();
        sos.close();
}

public Color getRandColor(int lower,int upper){
  Random random = new Random();
  if(upper>255)
   upper=255;
  if(upper<1)
   upper=1;
  if(lower<1)
   lower=1;
  if(lower>255)
   lower=255;
  int r=lower+random.nextInt(upper-lower);
  int g=lower+random.nextInt(upper-lower);
  int b=lower+random.nextInt(upper-lower);
  return new Color(r,g,b);
}
}
xml配置
  <servlet>
    <servlet-name>ImageServlet</servlet-name>
    <servlet-class>chenlh.ImageServlet</servlet-class>
  </servlet>
   <servlet-mapping>
    <servlet-name>ImageServlet</servlet-name>
    <url-pattern>/ImageServlet</url-pattern>
  </servlet-mapping>
HTML
<%@ page language="java" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
   + request.getServerName() + ":" + request.getServerPort()
   + path + "/";
%>
<script type="text/javascript" language="javascript">
  function changeImg(){
   var a=document.getElementById("mySpan");
   a.innerHTML='<img align="middle" src="ImageServlet"/>  <a href="#" onclick="changeImg();">看不清</a>'; //会复盖“mySpan”位置
  }
</script>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
  <meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
  <title>验证码</title>
</head>
<body>
  <span id="mySpan"><img align="middle" src="ImageServlet" /><a
   href="#" onclick="changeImg();">看不清</a> </span>
</body>
</html>
结果图