jsp生成动态验证码

<%@ page contentType="image/jpeg"

 import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*"%>

<%@ page contentType="image/jpeg" import="java.io.OutputStream"%>

<%

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

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

response.setDateHeader("Expires", 0);

int width=65, height=19;

BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

OutputStream os=response.getOutputStream(); 

Random random = new Random();

g.setColor(new Color(255,255,255));

g.fillRect(0, 0, width, height);

g.setFont(new Font("Times New Roman",Font.PLAIN,18));

g.setColor(new Color(255,255,255));//--del

for (int i=0;i<40;i++)

{      

     int x = random.nextInt(width);

        int y = random.nextInt(height);

        int xl = random.nextInt(12);

        int yl = random.nextInt(3);

        //g.setColor(new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255)));

        g.setColor(new Color(255,255,255));//--del

        g.drawLine(x,y,x+xl,y+yl);

}

String sRand="";

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

    int j = (random.nextInt(35) + 48);

    if(j > 57){

        j +=  8;

    }

    if(j == 48){

     j += random.nextInt(7)+1;

    }

    if(j == 49){

     j += random.nextInt(7)+1;

    }

    if(j == 73){

     j += random.nextInt(7)+1;

    }

    if(j == 79){

     j += random.nextInt(7)+1;

    }

    if(j == 111){

     j += random.nextInt(7)+1;

    }

   

    String rand=String.valueOf((char)j);

    sRand+=rand;

    g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));

    g.drawString(rand,13*i+6,16);

}

session.setAttribute("rand",sRand);

g.dispose();

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

os.flush();

os.close();

os=null;

response.flushBuffer();

out.clear();

out = pageContext.pushBody();  

%>