工具类_验证码

<%@page import="java.io.OutputStream"%>
<%@ page contentType="image/jpeg" pageEncoding="GBK" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" %>
<%!
	Color getRandColor(int fc,int bc){	//给定范围获得随机颜色
        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);
	}
%>
<%
//设置页面不缓存
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);

// 在内存中创建图象
int width=56, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

// 获取图形上下文
Graphics g = image.getGraphics();

//生成随机类
Random random = new Random();

// 设定背景色
//g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);

//设定字体
g.setFont(new Font("Courier New", Font.PLAIN, 18));

//画边框
//g.setColor(new Color(55,55,55));
//g.drawRect(0,0,width-1,height-1);

// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
g.setColor(getRandColor(160,200));
/*for (int i=0;i<155;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);
}*/

// 取随机产生的认证码(4位数字)
String sRand="";
for (int i=0;i<4;i++){
    String rand=String.valueOf(random.nextInt(10));
    sRand+=rand;
    // 将认证码显示到图象中
    g.setColor(new Color(20+random.nextInt(10),20+random.nextInt(110),20+random.nextInt(210)));
	//调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
    g.drawString(rand, 13*i+3, 16);
}
String sessionName = request.getParameter("VIName");
// 将认证码存入SESSION
if(sessionName==null) sessionName = "";
session.setAttribute("will_session_randCode_"+sessionName, sRand);

// 图象生效
g.dispose();

// 输出图象到页面
OutputStream os = response.getOutputStream();
ImageIO.write(image, "JPEG", os);
os.flush();
os.close();
response.flushBuffer();
out.clear();
out = pageContext.pushBody();
%>