java验证码

做项目时用到了验证码，整理了一下，分享给大家。

验证码中包含了数字和字母

1、 新建一个image.在image.jsp中写入以下代码：

<%@ page contentType="image/jpeg" import="java.awt.*,java.awt.image.*,java.util.*,javax.imageio.*" pageEncoding="UTF-8" %><%!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=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)String sRand="";// String data="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"; String[] num=new String[] {"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","1","2","3","4","5","6","7","8","9","0"};for (int i=0;i<4;i++){   String r=String.valueOf(random.nextInt(36));int s=Integer.parseInt(r);String rand=num[s];    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SESSIONsession.setAttribute("ValidateCode",sRand);// 图象生效g.dispose();// 输出图象到页面ImageIO.write(image, "JPEG", response.getOutputStream());//必须加上这两句话，否则报异常。out.clear();out = pageContext.pushBody();%> 

2、在login.html中写入以下代码：

<form action="checklogin.jsp">name:<input type="text" name="UserName"/><br/>pass:<input type="text" name="UserPwd"/><br/>vcode:<input type="text" name="ValidateCode"/><!-- <img src="image.jsp"/> --><img id="myImg" alt="眼不好使？" style="cursor:pointer;" title="眼不好使？点更换！" onclick="this.src='image.jsp?'+Math.random()" src="image.jsp"/><a href="javascript:void(0);" onclick="document.getElementById('myImg').src='image.jsp?'+Math.random()">看不清楚？点击刷新</a><br/><input type="submit" value="login"/></form>

3、在checklogin.jsp中写入一下代码：

<%String name=request.getParameter("UserName");String pwd=request.getParameter("UserPwd");String vcode=request.getParameter("ValidateCode");if(session.getAttribute("ValidateCode").equals(vcode)){//进行用户名密码的验证}else{//直接将请求打回，告诉其验证码不正确！out.println("<script>alert('验证码不正确！');location.href='login.html';</script>");}%>

效果图：