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JAVA登录验证码的实现

2018-03-14 21:42 507 查看

对于登录验证码，相信大家都不陌生，在一般的网站的登录时都会要求你输入验证码，这样可以有效保护你的账户的安全，防止黑客无限尝试登录暴力破解密码，也可以减少网站的垃圾数据。下面我们来使用java servlet来实现登录验证码的功能。

首先创建一个web项目，我们这里给出一个很简陋的jsp页面进行前端展示，主要是为了实现验证的额功能。下面贴出代码：

index.jsp:

<%@ 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>
<base href="<%=basePath%>">

<title>My JSP 'index.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">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
<script type="text/javascript">
function reload(){
var time=new Date().getTime();
document.getElementById("code").src="<%=request.getContextPath()%>/servlet/ImageServlet?time="+time;
}

</script>
</head>

<body>
<form action="<%=request.getContextPath()%>/servlet/VerifyServlet" method="get">
验证码：<input type="text" name="verifyCode" />
<img id="code" alt="验证码" src="<%=request.getContextPath()%>/servlet/ImageServlet"/>
<a  href="javascript:reload();">看不清楚</a>
<input type="submit" value="提交"/>
</form>
</body>
</html>

下面有两个servlet，在ImageServlet中我们会画出验证码图片，VerifyServlet中实现验证码的验证，看看前端提交过来的数据是否正确。

ImageServlet.java:

package cn.just;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ImageServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
BufferedImage bi=new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB);
Graphics g=bi.getGraphics();
Color c=new Color(200, 150, 255);
g.setColor(c);
g.fillRect(0, 0, 68, 22);
char[] ch="ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890".toCharArray();
Random r=new Random();
StringBuffer buffer=new StringBuffer();
int len=ch.length,index;
for(int i=0;i<4;i++){
index=r.nextInt(len);
g.setColor(new Color(r.nextInt(88), r.nextInt(188), r.nextInt(255)));
g.drawString(ch[index]+"", (i*15)+3, 18);
buffer.append(ch[index]);
}
req.getSession().setAttribute("verifyCode", buffer.toString());
ImageIO.write(bi, "JPG", resp.getOutputStream());
}
}

VerifyServlet.java:

package cn.just;

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;

public class VerifyServlet extends HttpServlet{
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
String code=req.getParameter("verifyCode");
String verifyCode=(String) req.getSession().getAttribute("verifyCode");
resp.setContentType("text/html;charset=UTF-8");
PrintWriter out=resp.getWriter();
if(code.equals(verifyCode)){
out.println("验证码正确");
System.out.println("验证码正确");
}else{
out.println("验证码错误");
}
out.flush();
out.close();
}
}

最后是web.xml配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
<display-name>Servlet_VerifyCode</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>ImageServlet</servlet-name>
<servlet-class>cn.just.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ImageServlet</servlet-name>
<url-pattern>/servlet/ImageServlet</url-pattern>
</servlet-mapping>

<servlet>
<servlet-name>VerifyServlet</servlet-name>
<servlet-class>cn.just.VerifyServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>VerifyServlet</servlet-name>
<url-pattern>/servlet/VerifyServlet</url-pattern>
</servlet-mapping>

</web-app>

至此，我们已经实现了验证码的验证功能，还有很多种方式来实现验证码功能，这里就使用servlet来实现，希望对大家有用。

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