一段利用session生成随即验证码得代码分享

importjava.awt.Color;
importjava.awt.Font;
importjava.awt.Graphics;
importjava.awt.image.BufferedImage;
importjava.io.ByteArrayOutputStream;
importjava.io.IOException;

importjavax.imageio.ImageIO;
importjavax.servlet.ServletException;
importjavax.servlet.ServletOutputStream;
importjavax.servlet.http.HttpServlet;
importjavax.servlet.http.HttpServletRequest;
importjavax.servlet.http.HttpServletResponse;
importjavax.servlet.http.HttpSession;


publicclassCheckextendsHttpServlet...{

privatestaticintWIDTH=60;
privatestaticintHEIGHT=20;

publicvoiddoGet(HttpServletRequestrequest,HttpServletResponseresponse)
throwsServletException,IOException...{
HttpSessionsession=request.getSession();
response.setContentType("image/jpeg");
ServletOutputStreamsos=response.getOutputStream();

//设置浏览器不要缓存图片
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires",0);

//创建内存图像并获得图像上下文
BufferedImageimage=newBufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
Graphicsg=image.getGraphics();

//产生随即得验证码
char[]rands=this.generateCheckCode();
//产生图像
this.drawBackground(g);
this.drawRands(g,rands);

//结束图像得绘制过程，完成图像
g.dispose();

//将图像输出到客户端
ByteArrayOutputStreambos=newByteArrayOutputStream();
ImageIO.write(image,"JPEG",bos);
byte[]buf=bos.toByteArray();
response.setContentLength(buf.length);
bos.write(buf);
bos.close();

//将验证码放入到session中
session.setAttribute("check_code",newString(rands));


}
privatechar[]generateCheckCode()...{
//定义验证码得字符表
Stringchars="0123456789abcdefghijklmnopqrstuvwxyz";
char[]rands=newchar[4];
for(inti=0;i<4;i++)...{
intrand=(int)(Math.random()*36);
rands[i]=chars.charAt(i);
}
returnrands;
}


privatevoiddrawRands(Graphicsg,char[]rands)...{
g.setColor(Color.BLACK);
g.setFont(newFont(null,Font.ITALIC|Font.BOLD,18));
g.drawString(""+rands[0],1,17);
g.drawString(""+rands[0],16,15);
g.drawString(""+rands[0],31,18);
g.drawString(""+rands[0],46,16);


}

privatevoiddrawBackground(Graphicsg)...{
//画背景
g.setColor(newColor(0xDCDCDC));
g.fillRect(0,0,WIDTH,HEIGHT);
for(inti=0;i<120;i++)...{
intx=(int)(Math.random()*WIDTH);
inty=(int)(Math.random()*HEIGHT);
intred=(int)(Math.random()*255);
intgreen=(int)(Math.random()*255);
intblue=(int)(Math.random()*255);
g.setColor(newColor(red,green,blue));
g.drawOval(x,y,1,0);
}
}


}