Java随机码

package servlet;

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

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
/**
* 生成随机验证码
* @author cuiran
* @date 2009-1-20
*
*/

@SuppressWarnings("serial")
public class ValidateCodeServlet extends HttpServlet {


//验证图片的宽度
private int width=60;
//验证图片的高度
private int height=20;
//验证码字符个数
private int codeCount=4;
private int x=0;
//字体高度
private int fontHeight;
private int codeY;
char[] codeSequence={'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
'X', 'Y', 'Z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9' };
public ValidateCodeServlet() {
super();
}


public void destroy() {
super.destroy();
}


public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}


public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
//定义图像buffer
BufferedImage buffImg=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
Graphics2D g=buffImg.createGraphics();
//创建一个随机数生成器类
Random random=new Random();
//将图像填充为白色
g.setColor(Color.WHITE);
g.fillRect(0, 0, width, height);
//创建字体，字体的大小应该根据图片的高度来定
Font font=new Font("Fixedsys",Font.PLAIN,fontHeight);

//设置字体
g.setFont(font);

//画边框
g.setColor(Color.BLACK);
g.drawRect(0, 0, width-1, height-1);
//随机产生160条干扰线，使图像中的认证码不易被其他程序探测到
g.setColor(Color.BLACK);
for(int i=0;i<160;i++){
int x=random.nextInt(width);
int y=random.nextInt(height);
int x1=random.nextInt(12);
int y1=random.nextInt(12);
g.drawLine(x, y, x+x1, y+y1);

}
//randomCode用于保存随机产生的验证码，以便用户登录后进行验证
StringBuffer randomCode=new StringBuffer();
int red=0,green=0,blue=0;

//随机产生codeCount数字的验证码
for(int i=0;i<codeCount;i++){
//得到随机产生的验证码数字
String strRand=String.valueOf(codeSequence[random.nextInt(36)]);
//产生随机的颜色分量来构造颜色值，这样输出的每位数字的颜色值都将不同
red=random.nextInt(255);
green=random.nextInt(255);
blue=random.nextInt(255);

//用随机产生的颜色将验证码绘制到图像中
g.setColor(new Color(red,green,blue));
g.drawString(strRand, (i+1)*x, codeY);
//将产生的四个随机数组合在一起。
randomCode.append(strRand);

}

//将四位数字的验证码保存到session中
HttpSession session=request.getSession();
session.setAttribute("validataCode", randomCode.toString());


//禁止图像缓存
response.setHeader("Paragma", "no-cache");
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expires", 0);

response.setContentType("image/jpeg");
//将图像输出到servlet输出流中
ServletOutputStream sos=response.getOutputStream();
ImageIO.write(buffImg, "jpeg", sos);
sos.close();
request.getRequestDispatcher("/index.jsp").include(request, response);
}
/**
* 初始化验证图片属性
*/
public void init() throws ServletException {
//从web.xml中获取初始信息
//宽度
String strWidth=this.getInitParameter("width");
//高度
String strHeight=this.getInitParameter("height");
//字符个数
String strCodeCount=this.getInitParameter("codeCount");
//将配置信息转换成数值
try{
if(strWidth!=null&&strWidth.length()!=0){
width=Integer.parseInt(strWidth);
}
if(strHeight!=null&&strHeight.length()!=0){
height=Integer.parseInt(strHeight);
}
if(strCodeCount!=null&strCodeCount.length()!=0){
codeCount=Integer.parseInt(strCodeCount);
}
}catch(NumberFormatException e){

}
x=width/(codeCount+1);
fontHeight=height-2;
codeY=height-4;
}

}