带有验证码的登录页面

用户名:

密码:

验证码:

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

import java.awt.*;

import java.awt.image.*;

import javax.imageio.ImageIO;

public class CheckCodeServlet extends HttpServlet

{

private static int WIDTH=60;

private static int HEIGHT=20;

public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException

{

HttpSession session = request.getSession();

response.setContentType("image/jpeg");

ServletOutputStream sos=response.getOutputStream();

//设置浏览器不要缓存此图片

response.setHeader("Pragma","No-cache");

response.setHeader("Cache-Control","no-cache");

response.setDateHeader("Expires",0);

//创建内容图片并获得其图形上下文

BufferedImage image=new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);

Graphics g=image.getGraphics();

//产生随机的验证码

char[] rands=generateCheckCode();

//产生图像

drawBackground(g);

drawRands(g,rands);

//结束图像的绘制过程,完成图像

g.dispose();

//将图像输出到客户端

ByteArrayOutputStream bos=new ByteArrayOutputStream();

ImageIO.write(image,"JPEG",bos);

byte[] buf=bos.toByteArray();

response.setContentLength(buf.length);

//下面的语句也可以写成:bos.writeTo(sos);

sos.write(buf);

bos.close();

sos.close();

//将当前验证码存入到session中

session.setAttribute("check_code",new String(rands));

}

private char[] generateCheckCode()

{

//定义验证码的字符表

String chars="0123456789abcdefghijklmnopqrstuvwxyz";

char[] rands=new char[4];

for(int i=0;i<4;i++)

{

int rand=(int)(Math.random()*36);

rands[i]=chars.charAt(rand);

}

return rands;

}

private void drawRands(Graphics g,char[] rands)

{

g.setColor(Color.BLACK);

g.setFont(new Font(null,Font.ITALIC|Font.BOLD,18));

//在不同的高度上输出验证码的每个字符

g.drawString(""+rands[0],1,17);

g.drawString(""+rands[1],16,15);

g.drawString(""+rands[2],31,87);

g.drawString(""+rands[3],46,16);

System.out.println(rands);

}

private void drawBackground(Graphics g)

{

//画背景

g.setColor(new Color(0xDCDCDC));

g.fillRect(0,0,WIDTH,HEIGHT);

//随即产生120个干扰点

for(int i=0;i<120;i++)

{

int x=(int)(Math.random()*WIDTH);

int y=(int)(Math.random()*HEIGHT);

int red=(int)(Math.random()*255);

int green=(int)(Math.random()*255);

int blue=(int)(Math.random()*255);

g.setColor(new Color(red,green,blue));

g.drawOval(x,y,1,0);

}

}

}

import java.io.*;

import javax.servlet.*;

import javax.servlet.http.*;

public class LogonFormServlet extends HttpServlet

{

public void service(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException

{

response.setContentType("text/html;charset=GB2312");

PrintWriter out=response.getWriter();

HttpSession session=request.getSession(false);

if(session==null)

{

out.println("验证码处理问题!");

return ;

}

String savedCode=(String)session.getAttribute("check_code");

if(savedCode==null)

{

out.println("验证码处理问题!");

return ;

}

String checkCode=request.getParameter("check_code");

if(!savedCode.equals(checkCode))

{

/*验证码未通过,不从session中清楚原来的验证码,

以便用户可以后退回登录页面继续使用原来的验证码进行登录*/

out.println("验证码无效!");

return ;

}

/*验证码检查通过后,从session中清楚原来的验证码,

以防用户后退回登录页面继续使用原来的验证码进行登录*/

session.removeAttribute("check_code");

out.println("验证码通过,服务器正在校验用户名和密码!");

}

}

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2009-01-07 15:14

浏览 1237

评论

1 楼

wenniuwuren

2012-04-01

不能显示图片..