一段生成验证码图片的程序

代码:package test;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.OutputStream;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


public class ImageGenerator extends HttpServlet {
/**
*
*/
private static final long serialVersionUID = -3938318741402322164L;

private static Color getRandColor(int fc, int bc) {
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);
}

private static String charsLong = "23456789abcdefghjklmnpqrstuvwxyzABCDEFGHIJKLMNPQRSTUVWXYZ";

private static String charsShort = "0123456789";

private static String chars = charsLong;

@Override
public void doGet(HttpServletRequest request, HttpServletResponse response) {
try {
int charsLength = chars.length();

response.setHeader("ragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);

int width = 70, height = 20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics g = image.getGraphics();

Random random = new Random();

g.setColor(getRandColor(200, 250));
g.fillRect(0, 0, width, height);

g.setFont(new Font("Times New Roman", Font.ITALIC, height));

g.setColor(getRandColor(160, 200));
for (int i = 0; i < 35; i++) {
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(12);
int yl = random.nextInt(12);
g.drawLine(x, y, x + xl, y + yl);
}

StringBuilder sRand = new StringBuilder();
String[] fontNames = { "Times New Roman", "Arial", "Book antiqua", "" };

for (int i = 0; i < 4; i++) {
g.setFont(new Font(fontNames[random.nextInt(3)], Font.ITALIC, height));
char rand = chars.charAt(random.nextInt(charsLength));
sRand.append(rand);

g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));
g.drawString(String.valueOf(rand), 16 * i + random.nextInt(6) + 3, height - random.nextInt(4));
}

g.setColor(getRandColor(160, 200));
for (int i = 0; i < 30; i++) {
int x = random.nextInt(width);
int y = random.nextInt(height);
int xl = random.nextInt(width);
int yl = random.nextInt(width);
g.drawLine(x, y, x + xl, y + yl);
}

request.getSession().setAttribute("Login_Image_Code", sRand.toString());

g.dispose();

try {
Thread.sleep(100);
} catch (Exception ex) {
}
OutputStream os = response.getOutputStream();
ImageIO.write(image, "JPEG", os);
os.flush();
os.close();
} catch (Exception ex) {

}
}
}


修改 web.xml
代码:
<servlet>
         <servlet-name>imageGenerator</servlet-name>
         <servlet-class>test.ImageGenerator</servlet-class>
     </servlet>
     <servlet-mapping>
         <servlet-name>imageGenerator</servlet-name>
         <url-pattern>/image.jsp</url-pattern>
     </servlet-mapping>