Java笔记-使用Kaptcha验证码框架

大家好，又见面了，我是你们的朋友全栈君。

使用Kaptcha这个验证码框架用起来，比自己写简单

首先设置maven项目：

        <dependency>
            <groupId>com.github.penggle</groupId>
            <artifactId>kaptcha</artifactId>
            <version>2.3.2</version>
        </dependency>

然后配置WEB-INF下的web.xml

<!DOCTYPE web-app PUBLIC
        "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
        "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
    <display-name>Archetype Created Web Application</display-name>

    <servlet-mapping>
        <servlet-name>kaptchaDemo</servlet-name>
        <url-pattern>/kaptcha</url-pattern>
    </servlet-mapping>
    
    <servlet>
        <servlet-name>kaptchaDemo</servlet-name>
        <servlet-class>com.google.code.kaptcha.servlet.KaptchaServlet</servlet-class>
        <init-param>
            <param-name>kaptcha.border</param-name>
            <param-value>no</param-value>
        </init-param>
        <init-param>
            <param-name>kaptcha.textproducer.font.color</param-name>
            <param-value>red</param-value>
        </init-param>
        <init-param>
            <param-name>kaptcha.image.width</param-name>
            <param-value>80</param-value>
        </init-param>
        <init-param>
            <param-name>kaptcha.image.height</param-name>
            <param-value>30</param-value>
        </init-param>
        <init-param>
            <param-name>kaptcha.textproducer.char.string</param-name>
            <param-value>0123456789</param-value>
        </init-param>
        <init-param>
            <param-name>kaptcha.textproducer.char.length</param-name>
            <param-value>4</param-value>
        </init-param>
        <init-param>
            <param-name>kaptcha.textproducer.char.space</param-name>
            <param-value>3</param-value>
        </init-param>
        <init-param>
            <param-name>kaptcha.textproducer.font.size</param-name>
            <param-value>24</param-value>
        </init-param>
<!--        <init-param>-->
<!--            <param-name>kaptcha.noise.impl</param-name>-->
<!--            <param-value>com.google.code.kaptcha.impl.NoNoise</param-value>-->
<!--        </init-param>-->
    </servlet>

</web-app>

其中对应的jsp页面如下：

<%@ 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>kaptchaDemo</title>
    <style type="text/css">
        .code_a{
            color: #0000ff;
            font-size: 12px;
            text-decoration: none;
            cursor: pointer;
        }
        #imgCode{
            cursor: pointer;
        }
    </style>
    <script type="text/javascript">
        function changeCode(){
            var imgCode = document.getElementById("imgCode");
            imgCode.src = "kaptcha?"+Math.random();
        }
    </script>
</head>

<body>
<form action="login" method="post">
    <label>验证码：</label>
    <input type="text" id="inCode" name="inCode" />
    <img src="kaptcha" align="center" id="imgCode" onclick="changeCode()" />
    <a class="code_a" onclick="changeCode()">换一张</a><br />
    <input type="submit" value="登录"/>
</form>
</body>
</html>

这里src请求的是kaptcha的url。这里这个框架里面实现了一个Servlet，通过配置文件的方式，对某些属性进行设置（这里不用说了，肯定是反射）

程序运行截图如下：

输入错误时，依旧是这个界面，但输入正确后！

下面是关于他的验证方面的代码：

LoginServlet.java

import com.google.code.kaptcha.Constants;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebServlet(value = "/login")
public class LoginServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        this.doPost(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        String vailCode = request.getSession().getAttribute(Constants.KAPTCHA_SESSION_KEY).toString().toLowerCase();
        String inCode = request.getParameter("inCode").toLowerCase();

        if(inCode.equals(vailCode)){

            response.sendRedirect("success.jsp");
        }
        else{

            String url = request.getHeader("Referer");
            response.sendRedirect(url);
        }
    }
}