JSP验证码

浏览数：41 / 时间：2015年06月09日

1、login.jsp登陆界面

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Login Page</title>

<script language="javascript">
	function loadImage()
	{
		document.getElementById("randImage").src="image.jsp?"+Math.random();
	}
</script>

</head>
<body>
<form action="validate.jsp" method="post">
<table cellspacing="1" cellpadding="3" border="0">
	<tr>
		<td colspan="2">Please enter your verification code</td>
	</tr>
	<tr>
		<td><input type="text" name="vcode"/></td>
		<td><img src="image.jsp" id="randImage"/></td>
	</tr>
	<tr>
		<td colspan="2"><a href="javascript:loadImage()">Change an image</a></td>
	</tr>
	<tr>
		<td colspan="2"><input type="submit" value="Submit"/></td>
	</tr>
</table>
</form>
</body>
</html>

2、image.jsp生成验证码图片的jsp文件

<%@ page language="java"%>
<%@ page import="java.awt.*,java.awt.image.*,java.util.*" %>
<%@ page import="java.io.OutputStream,javax.imageio.*"%>

<%!
	Color getRandColor(int fc,int bc){
		if(fc>255){
			fc=255;
		}
		if(bc>255){
			bc=255;
		}
		Random random=new Random();
		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);
	}
%>
<%
	//本地无缓存,每次自动刷新
	response.addHeader("pragma", "No-cashe");
	response.addHeader("cashe-control","no-cashe");
	response.setDateHeader("expires",0);
	
	int width=60,height=20;
	BufferedImage bimg=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
	Graphics g=bimg.getGraphics();
	g.setColor(getRandColor(200,250));
	g.fillRect(0, 0, width, height);
	g.setColor(getRandColor(160,200));
	Random rand=new Random();
	for(int i=0;i<200;i++){
		int x=rand.nextInt(width);
		int y=rand.nextInt(height);
		int w=rand.nextInt(12);
		int h=rand.nextInt(12);
		g.drawLine(x, y, x+w, y+h);
	}
	
	String srand="";
	g.setFont(new Font("Times New Roman",Font.PLAIN,18));
	for(int i=0;i<4;i++){
		String num=String.valueOf(rand.nextInt(10));
		srand+=num;
		g.setColor(new Color(20+rand.nextInt(110),20+rand.nextInt(110),20+rand.nextInt(110)));
		g.drawString(num, 13*i+6, 16);
	}
	
	session.setAttribute("srand", srand);
	
	OutputStream os=response.getOutputStream();
	ImageIO.write(bimg, "jpeg", os);
	
	os.flush();
	os.close();
	os=null;
	g.dispose();
	
	//这两句非常重要，如果没有会报错
	out.clear();
	out=pageContext.popBody();
%>

3、validate.jsp对验证码进行验证

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Validate Page</title>
</head>
<body>
<%
	String str=(String)session.getAttribute("srand");
	String incode=request.getParameter("vcode");
	if(str.equals(incode)){
		out.println("<font size=\"+3\" color=\"#000\">The verification is right!</font><br/>");
		out.println("<font size=\"+4\" color=\"#FF0000\">Welcone to the page!</font><br/><hr/>");
	}else{
		out.println("<font size=\"+4\" color=\"#FF0000\">"
				+"Sorry the verification code is not right</font></br><hr>");
	}
	out.println("<br/><a href=\"login.jsp\">Back to the login page</a>");
%>
</body>
</html>