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jsp生成验证码图片的程序
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;
public void doGet(HttpServletRequest request, HttpServletResponse response) ...{
try ...{
int charsLength = chars.length();
response.setHeader("Pragma", "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
<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>
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