jsp中验证码的实现

素颜马尾好姑娘i 2022-09-30 13:51 178阅读 0赞

<%@ page language="java" import="java.awt.\*,java.awt.image.\*,java.util.\*,javax.imageio.\*" pageEncoding="gbk"%>  
<%@ page contentType="image/jpeg;charset=GBK" %>

<%  
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>  
    <base href="<%=basePath%>">  
      
    <title>My JSP 'MyJsp.jsp' starting page</title>  
      
 <meta http-equiv="pragma" content="no-cache">  
 <meta http-equiv="cache-control" content="no-cache">  
 <meta http-equiv="expires" content="0">      
 <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">  
 <meta http-equiv="description" content="This is my page">

</head>  
    
  <body>  
    <%!  
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);  
        \}  
%>

out.clear(); //加上这句     
out = pageContext.pushBody(); //还有这句就OK了     
//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;  
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("Times New Roman",Font.PLAIN,18));

//画边框  
//g.setColor(new Color());  
//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(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);  
\}  
// 将认证码存入SESSION  
session.setAttribute("rand",sRand);  
// 图象生效  
g.dispose();  
// 输出图象到页面  
//ImageIO.setUseCache(true);  
ServletOutputStream stream = null ;  
stream = response.getOutputStream();  
ImageIO.write(image, "JPEG",stream);  
%>  
 </body>  
</html>