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");

}