radnom(6wei).jsp

java的一个验证码程序

<%@ page language="java"  pageEncoding="gb2312"%>
<%@ page contentType="image/jpeg" %>
<%@ page import="java.awt.*,java.awt.image.*" %>
<%@ page import="java.util.*,javax.imageio.*" %>

<%!
//产生随机颜色函数
	Color getRandColor(int fc,int bc){
		Random r=new Random();
		if(fc>255) fc=255;
		if(bc>255) bc=255;
		int red=fc+r.nextInt(bc-fc);
		int green=fc+r.nextInt(bc-fc);
		int blue=fc+r.nextInt(bc-fc);
		return new Color(red,green,blue);
	}
 %>
 <%
 //设置页面不缓存
 	response.setHeader("Pragma","NO-cache");
 	response.setHeader("Cache-Control","no-cache");
 	response.setDateHeader("Expires",0);
 	
 //创建随机类
 	Random r=new Random();
 	
 //在内存中创建图像，宽度为width,高度为height
 	int width=90,height=20;
 	BufferedImage pic=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
 
 //获取图形上下文环境
 	Graphics gc=pic.getGraphics();
 
 //设定背景色并进行填充
 	gc.setColor(getRandColor(200,250));
 	gc.fillRect(0,0,width,height);
 	
 //设定图形上下文环境字体
 	gc.setFont(new Font("Times New Roman",Font.PLAIN,18));
 	
 //随机产生200条干扰直线，使图像中的认证码不易被其他分析程序探测到
 	gc.setColor(getRandColor(160,200));
 	for(int i=0;i<200;i++){
 		int x1=r.nextInt(width);
 		int y1=r.nextInt(height);
 		int x2=r.nextInt(15);
 		int y2=r.nextInt(15);
 		gc.drawLine(x1,y1,x2,y2);
 		
 	}
 //随机产生100个干扰点
 	gc.setColor(getRandColor(120,240));
 	for(int i=0;i<100;i++){
 		int x=r.nextInt(width);
 		int y=r.nextInt(height);
 		gc.drawOval(x,y,0,0);
 	}
 	
 //随机产生4位数字的验证码
 	String RS="";
 	String rn="";
 	for(int i=0;i<6;i++){
 		//产生10以内的随机数字rn
 		rn=String.valueOf(r.nextInt(10));
 		RS+=rn;
 		//将认证码用drawString函数显示到图像里
 		gc.setColor(new Color(20+r.nextInt(110),20+r.nextInt(110),20+r.nextInt(110)));
 		gc.drawString(rn,13*i+6,16);
 		}
 //释放图形上下文环境
 	gc.dispose();
 
 //将认证码RS存放到session中共享
 	session.setAttribute("random",RS);
 	
 //输出生成后的验证码图像到页面
 	ImageIO.write(pic,"JPEG",response.getOutputStream());
 	
  %>