一个生成验证码的类

package com.huawei.tsm.business.login.common;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.huawei.bme.commons.om.log.DebugLog;
import com.huawei.bme.commons.om.log.LogFactory;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

/**
*
* 验证码生成类
* @author zxp
* @version MTV Portal V100R001C01 2009-2-5
* @since MTV Portal V100R001C01
*/
public class RandomPictrueServlet extends HttpServlet
{
/**
*
*/
private static final long serialVersionUID = 1L;

/**
* 日志实例
*/
private final static DebugLog debugLog = LogFactory.getDebugLog(RandomPictrueServlet.class);

private static final String CONTENT_TYPE = "image/jpeg";

private static final int WIDTH = 70;

private static final int HEIGHT = 18;

private static final int LENGTH = 4;

public static final String SESSION_AUTHEN_CODE = "session_picCode";

// Initialize global variables
public void init() throws ServletException
{
}

// Process the HTTP Get request
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException
{

response.setContentType(CONTENT_TYPE);
response.setHeader("Pragma", "No-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);
int width = WIDTH;
int height = HEIGHT;
int length = LENGTH;
String sessionName = request.getParameter("authenName");
if ((null == sessionName) || ("".equals(sessionName.trim())))
{
sessionName = SESSION_AUTHEN_CODE;
}
try
{
width = Integer.parseInt(request.getParameter("width"));
}
catch (Exception ex)
{
width = WIDTH;
}
try
{
height = Integer.parseInt(request.getParameter("heigth"));
}
catch (Exception ex)
{
height = HEIGHT;
}
try
{
length = Integer.parseInt(request.getParameter("length"));
}
catch (Exception ex)
{
length = LENGTH;
}
try
{

Random ran = new Random(System.currentTimeMillis());

String seed = (ran.nextInt() + "").substring(1, 1 + length);

request.getSession().setAttribute(sessionName, seed);

StringBuffer sb = new StringBuffer();
for (int i = 0; i < seed.length(); i++)
{
sb.append(seed.charAt(i) + " ");
}
String sb_str = sb.toString();

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

Graphics2D g = (Graphics2D) image.getGraphics();

g.setColor(new Color(198, 221, 254));

g.fillRect(0, 0, width, height);
g.setColor(new Color(165, 199, 255));
g.drawRect(0, 0, width - 1, height - 1);
g.setColor(new Color(255, 255, 255));
g.drawRect(1, 1, width - 3, height - 3);

g.setColor(Color.DARK_GRAY);

for (int i = 0; i < 4; i++)
{
int x_b = ran.nextInt(width);
int x_e = ran.nextInt(width);
int y_b = ran.nextInt(height + 10);
int y_e = ran.nextInt(height + 10);
g.drawLine(x_b, y_b, x_e, y_e);
}

g.setFont(new Font("System", Font.BOLD, 14));

g.drawString(sb_str, 5, 15);

g.dispose();
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(response.getOutputStream());
encoder.encode(image);
}
}
catch (Exception ex)
{
debugLog.error(ex.toString(), ex);
}
}

// Clean up resources
public void destroy()
{
}
}