使用servlet编写一个验证码的例子

使用servlet编写一个验证码的例子
package com.topsuntech.gUnit_cnpo.common.servlet;

import java.io.*;
import java.util.*;
import com.sun.image.codec.jpeg.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;

/*
* 功能：调用AuthServlet可以生成一个验证码图片,图片的宽度和高度可以自定义
* 调用格式: /servlet/AuthServlet?width=60&height=20
*       或者/servlet/AuthServlet
* 时间：2007-9-4
* 
*
*/
public class AuthServlet extends HttpServlet {
private Font mFont=new Font("Times New Roman", Font.PLAIN,18);//设置字体
//static String AuthCode="";

// 处理post
public void doPost(HttpServletRequest request,HttpServletResponse response)
throws ServletException,IOException {
    doGet(request,response);
}

public void doGet(HttpServletRequest request,HttpServletResponse response)
      throws ServletException,IOException {
// 取得一个1000-9999的随机数


      HttpSession session=request.getSession();//request.getSession(false)当参数为false时，有可能不创建session
      //session.setAttribute("getImg",s);
      response.setContentType("image/gif");
      response.setHeader("Pragma","No-cache");
      response.setHeader("Cache-Control","no-cache");
      response.setDateHeader("Expires", 0);
      int width=60;
      int height=20;
      if(request.getParameter("width")!=null && !request.getParameter("width").equals(""))
       width = Integer.parseInt(request.getParameter("width"));
      if(request.getParameter("height")!=null && !request.getParameter("height").equals(""))
       height = Integer.parseInt(request.getParameter("height"));
                

      ServletOutputStream out=response.getOutputStream();
      BufferedImage image=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB); //设置图片大小的
      Graphics gra=image.getGraphics();
      Random random=new Random();

      gra.setColor(getRandColor(200,250));     //设置背景色
      gra.fillRect(0,0,width,height);

      gra.setColor(Color.black); //设置字体色
      gra.setFont(mFont);


      // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
      gra.setColor(getRandColor(160,200));
      for (int i=0;i<155;i++)
      {
       int x = random.nextInt(width);
       int y = random.nextInt(height);
              int xl = random.nextInt(12);
              int yl = random.nextInt(12);
       gra.drawLine(x,y,x+xl,y+yl);
      }

      // 取随机产生的认证码(4位数字)
      String sRand="";
      for (int i=0;i<4;i++){
         String rand=String.valueOf(random.nextInt(10));
         sRand+=rand;
          // 将认证码显示到图象中
          gra.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));//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
          gra.drawString(rand,13*i+6,16);
      }
          //System.out.println("showimage="+sRand);
          //session.setAttribute("getImg",sRand);
          session.setAttribute("AuthCode",sRand);
          //AuthCode = sRand;
          //session.putValue("AuthCode",sRand);
          JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);
          encoder.encode(image);
          //out.flush();

}

    static Color getRandColor(int fc,int bc){//给定范围获得随机颜色
           Random random = new Random();
           if(fc>255) fc=255;
           if(bc>255) bc=255;
           int r=fc+random.nextInt(bc-fc);
           int g=fc+random.nextInt(bc-fc);
           int b=fc+random.nextInt(bc-fc);
           return new Color(r,g,b);
    }
  
    static public String getAuthCode(HttpSession session){//返回验证
     return (String)session.getAttribute("AuthCode");
         
    }