图片验证码（jsp）

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verifycode.jsp

<%@page contentType="image/JPEG" language="java" import= "crm.util.RandomNumUtil" pageEncoding="utf-8"%>
<%@page import="javax.imageio.ImageIO,java.awt.*,java.util.*,java.awt.image.BufferedImage"%>

<%!
//图像
BufferedImage image;
//验证码
String randCode;
%>

<%!
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);
}
%>

<%
//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=60, height=20;
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("Times New Roman",Font.PLAIN,18));

//画边框
//g.setColor(new Color());
//g.fillRect(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)
for (int i=0;i<4;i++){
    String rand=String.valueOf(random.nextInt(10));
    randCode+=rand;
    // 将认证码显示到图象中
    g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));

    //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+6,16);

}
session.setAttribute("code",randCode);
//图象生效
g.dispose();
ImageIO.write(image,"JPEG",response.getOutputStream());
%>
<%
    out.clear();                  /* This Sentence Is Necessary */
    out = pageContext.pushBody(); /* This Sentence Is Necessary */
%>

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>登陆界面</title>
</head>
<body>
<img src="<%=basePath%>pages/verifycode2.jsp"/>
</body>
</html>