页面随机验证码的兑现 _Web前端

页面随机验证码的实现

index.jsp:

<%@ page contentType="text/html;charset=utf-8"%>
<%@ page language="java" import="java.sql.*" errorPage=""%>
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
		<title>用户登录</title>
<!-- 此处需要引入JQuery的包-->
?<script type='text/javascript' src='js/jquery-latest.js'></script>
		<script language="javascript">
var murl="<%=request.getContextPath()%>/ValidateServlet";
alert(2);
function loadimage(){
	alert(1);
	document.getElementById("randImage").src = "image.jsp?"+Math.random();
}

//从ValidateServlet.java返回验证的结果是否正确
function check(){
	alert("check()");
	var num=document.getElementById("num").value;
	alert(num);
	$.post(murl,{num:num},function(data){
		alert(data);	
	});
}

</script>
	</head>
	<body>
		<table width="256" border="0" cellpadding="0" cellspacing="0">
			<!--DWLayoutTable-->
			<form name="loginForm">
				<tr>
					<td width="118" height="22" valign="middle" align="center">
						<input type="text" id="num" size="15">
					</td>
					<td width="138" valign="middle" align="center">
						<img name="randImage" id="randImage" src="image.jsp" width="60"
							height="20" border="1" align="absmiddle">
					</td>
				</tr>
				<tr>
					<td height="36" colspan="2" align="center" valign="middle">
						<a href="javascript:loadimage();"><font class=pt95>看不清点我</font>
						</a>
					</td>
				</tr>
				<tr>
					<td height="36" colspan="2" align="center" valign="middle">
						<input type="button" onclick="javascript:check()" name="login"
							value="提交">
					</td>
				</tr>
			</form>
		</table>
	</body>
</html>

image.jsp:

<%@ page contentType="image/jpeg"
	import="java.awt.*,
java.awt.image.*,java.util.*,javax.imageio.*"
	pageEncoding="utf-8"%>
	<%@ page import="java.io.OutputStream" %>
<%!
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);
}
%>
<%
try{
response.setHeader("Pragma","No-cache");
response.setHeader("Cache-Control","no-cache");
response.setDateHeader("Expires", 0);
int width=60, height=20;
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
OutputStream os=response.getOutputStream();
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200,250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.PLAIN,18));
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);
}
String sRand="";
for (int i=0;i<4;i++){
String rand=String.valueOf(random.nextInt(10));
sRand+=rand;
g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
g.drawString(rand,13*i+6,16);
}
// 将认证码存入SESSION
session.setAttribute("rand",sRand);
g.dispose();
ImageIO.write(image, "JPEG", os);
os.flush();
os.close();
os=null;
response.flushBuffer();
out.clear();
out = pageContext.pushBody();
}catch(IllegalStateException e){
e.printStackTrace();
}
%>

ValidateServlet.java:

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


public class ValidateServlet extends HttpServlet {

	/**
	 * The doGet method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to get.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html;charset=utf-8");
		PrintWriter out = response.getWriter();
		HttpSession session=request.getSession();
		String rand = (String)session.getAttribute("rand");
                //得到用户输入的验证码
?               String input = request.getParameter("num");
		if(rand.equals(input)){
		out.print("success");
		} else{
		out.print("error");
		}
	}

	/**
	 * The doPost method of the servlet. <br>
	 *
	 * This method is called when a form has its tag value method equals to post.
	 * 
	 * @param request the request send by the client to the server
	 * @param response the response send by the server to the client
	 * @throws ServletException if an error occurred
	 * @throws IOException if an error occurred
	 */
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		this.doGet(request, response);
	}

}