Java如何实现kaptcha网页验证码验证

<!-- https://mvnrepository.com/artifact/com.github.penggle/kaptcha -->
		<dependency>
		    <groupId>com.github.penggle</groupId>
		    <artifactId>kaptcha</artifactId>
		    <version>2.3.2</version>
		</dependency> 

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<!-- 登陆验证码Kaptcha 2-->
<servlet>
	<servlet-name>Kaptcha</servlet-name>
	<servlet-class>
		com.google.code.kaptcha.servlet.KaptchaServlet
	</servlet-class>
	<init-param>
		<description>图片边框，合法值：yes , no</description>
		<param-name>kaptcha.border</param-name>
		<param-value>yes</param-value>
	</init-param>
	<init-param>
		<description>
			边框颜色，合法值： r,g,b (and optional alpha) 或者
			white,black,blue.
		</description>
		<param-name>kaptcha.border.color</param-name>
		<param-value>black</param-value>
	</init-param>
	<init-param>
		<description>边框厚度，合法值：>0</description>
		<param-name>kaptcha.border.thickness</param-name>
		<param-value>1</param-value>
	</init-param>
	<init-param>
		<description>图片宽 200</description>
		<param-name>kaptcha.image.width</param-name>
		<param-value>200</param-value>
	</init-param>
	<init-param>
		<description>图片高 50</description>
		<param-name>kaptcha.image.height</param-name>
		<param-value>50</param-value>
	</init-param>
	<init-param>
		<description>图片实现类</description>
		<param-name>kaptcha.producer.impl</param-name>
		<param-value>
			com.google.code.kaptcha.impl.DefaultKaptcha
		</param-value>
	</init-param>
	<init-param>
		<description>文本实现类</description>
		<param-name>kaptcha.textproducer.impl</param-name>
		<param-value>
			com.google.code.kaptcha.text.impl.DefaultTextCreator
		</param-value>
	</init-param>
	<init-param>
		<description>文本集合，验证码值从此集合中获取</description>
		<param-name>kaptcha.textproducer.char.string</param-name>
		<param-value>1234567890</param-value>
		  <!--<param-value>abcde2345678gfynmnpwx</param-value>-->
	</init-param>
	<init-param>
		<description>验证码长度 5</description>
		<param-name>kaptcha.textproducer.char.length</param-name>
		<param-value>5</param-value>
	</init-param>
	<init-param>
		<description>字体 Arial, Courier</description>
		<param-name>kaptcha.textproducer.font.names</param-name>
		<param-value>Arial, Courier</param-value>
	</init-param>
	<init-param>
		<description>字体大小 40px.</description>
		<param-name>kaptcha.textproducer.font.size</param-name>
		<param-value>40</param-value>
	</init-param>
	<init-param>
		<description>
			字体颜色，合法值： r,g,b 或者 white,black,blue.
		</description>
		<param-name>kaptcha.textproducer.font.color</param-name>
		<param-value>black</param-value>
	</init-param>
	<init-param>
		<description>文字间隔 2</description>
		<param-name>kaptcha.textproducer.char.space</param-name>
		<param-value>2</param-value>
	</init-param>
	<init-param>
		<description>干扰实现类</description>
		<param-name>kaptcha.noise.impl</param-name>
		<param-value>
			<!-- com.google.code.kaptcha.impl.NoNoise -->
			com.google.code.kaptcha.impl.DefaultNoise
		</param-value>
	</init-param>
	<init-param>
		<description>
			干扰颜色，合法值： r,g,b 或者 white,black,blue.
		</description>
		<param-name>kaptcha.noise.color</param-name>
		<param-value>black</param-value>
	</init-param>
	<init-param>
		<description>
			图片样式： 水纹com.google.code.kaptcha.impl.WaterRipple
			鱼眼com.google.code.kaptcha.impl.FishEyeGimpy
			阴影com.google.code.kaptcha.impl.ShadowGimpy
		</description>
		<param-name>kaptcha.obscurificator.impl</param-name>
		<param-value>
			com.google.code.kaptcha.impl.WaterRipple
		</param-value>
	</init-param>
	<init-param>
		<description>背景实现类</description>
		<param-name>kaptcha.background.impl</param-name>
		<param-value>
			com.google.code.kaptcha.impl.DefaultBackground
		</param-value>
	</init-param>
	<init-param>
		<description>背景颜色渐变，开始颜色</description>
		<param-name>kaptcha.background.clear.from</param-name>
		<param-value> black</param-value>
	</init-param>
	<init-param>
		<description>背景颜色渐变，结束颜色</description>
		<param-name>kaptcha.background.clear.to</param-name>
		<param-value>white</param-value>
	</init-param>
	<init-param>
		<description>文字渲染器</description>
		<param-name>kaptcha.word.impl</param-name>
		<param-value>
			com.google.code.kaptcha.text.impl.DefaultWordRenderer
		</param-value>
	</init-param>
	<init-param>
		<description>
			session中存放验证码的key键
		</description>
		<param-name>kaptcha.session.key</param-name>
		<param-value>KAPTCHA_SESSION_KEY</param-value>
	</init-param>
	<init-param>
		<description>
			生成kaptcha的日期被放入HttpSession中。这是会话中该项的键值。
		</description>
		<param-name>kaptcha.session.date</param-name>
		<param-value>KAPTCHA_SESSION_DATE</param-value>
	</init-param>
</servlet>
<servlet-mapping>
	<servlet-name>Kaptcha</servlet-name>
	<url-pattern>/randomcode.jpg</url-pattern>
</servlet-mapping>


<welcome-file-list>
	<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>randomcode</title>
<script type="text/javascript">
	function changeR(node){
		// 用于点击时产生不同的验证码
		node.src = "randomcode.jpg?time="+new Date().getTime() ;	
	}
</script>
</head>
<body>
<img alt="random" src="randomcode.jpg" onclick="changeR(this)" style="cursor: pointer;">
	<form action="check.jsp">
		<input type="text" name="r">
		<input type="submit" value="确认">
	</form>	
</body>
</html>

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!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=UTF-8">
<title>check</title>
</head>
<body>
	<%
		// 检查是否是正确的验证码
		String k = (String) session
				.getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
		String str = request.getParameter("r");
		str = new String(str.getBytes("iso-8859-1"),"utf-8");
		if (k.equals(str))
			out.print("输入验证码正确！");
		else
			out.print("输入验证码错误！！！");
		out.print("验证码为：" + k + ",你输入的验证码为：" + str);
	%>
</body>
</html>

<init-param>
			<description>文本实现类</description>
			<param-name>kaptcha.textproducer.impl</param-name>
			<param-value>
				com.kaptcha.ChineseText
			</param-value>
		</init-param>

package com.kaptcha;

import java.util.Random;

import com.google.code.kaptcha.text.TextProducer;
import com.google.code.kaptcha.util.Configurable;

public class ChineseText extends Configurable implements TextProducer {
	public String getText() {
		int length = getConfig().getTextProducerCharLength();
		String finalWord = "", firstWord = "";
		int tempInt = 0;
		String[] array = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
				"a", "b", "c", "d", "e", "f","g", "h", "i", "j", "k"};

		Random rand = new Random();

		for (int i = 0; i < length; i++) {
			switch (rand.nextInt(array.length)) {
			case 1:
				tempInt = rand.nextInt(26) + 65;
				firstWord = String.valueOf((char) tempInt);
				break;
			case 2:
				int r1,
				r2,
				r3,
				r4;
				String strH,
				strL;			// high&low
				r1 = rand.nextInt(3) + 11;
				if (r1 == 13) {
					r2 = rand.nextInt(7);
				} else {
					r2 = rand.nextInt(16);
				}

				r3 = rand.nextInt(6) + 10;
				if (r3 == 10) {
					r4 = rand.nextInt(15) + 1;
				} else if (r3 == 15) {
					r4 = rand.nextInt(15);
				} else {
					r4 = rand.nextInt(16);
				}

				strH = array[r1] + array[r2];
				strL = array[r3] + array[r4];

				byte[] bytes = new byte[2];
				bytes[0] = (byte) (Integer.parseInt(strH, 16));
				bytes[1] = (byte) (Integer.parseInt(strL, 16));

				firstWord = new String(bytes);
				break;
			default:
				tempInt = rand.nextInt(10) + 48;
				firstWord = String.valueOf((char) tempInt);
				break;
			}
			finalWord += firstWord;
		}
		return finalWord;
	}
}

<servlet-class>
			com.kaptcha.KaptchaServlet
		</servlet-class>

	<init-param>
	<description>文本实现类</description>
	<param-name>kaptcha.textproducer.impl</param-name>
	<param-value>
		com.google.code.kaptcha.text.impl.DefaultTextCreator
	</param-value>
</init-param>

		<init-param>
			<description>验证码长度 2</description>
			<param-name>kaptcha.textproducer.char.length</param-name>
			<param-value>2</param-value>
		</init-param>

package com.kaptcha;

import com.google.code.kaptcha.Producer;
import com.google.code.kaptcha.util.Config;

import javax.imageio.ImageIO;
import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;

public class KaptchaServlet extends HttpServlet implements Servlet {
	private Properties props;
	private Producer kaptchaProducer;
	private String sessionKeyValue;

	public KaptchaServlet() {
		this.props = new Properties();

		this.kaptchaProducer = null;

		this.sessionKeyValue = null;
	}

	public void init(ServletConfig conf) throws ServletException {
		super.init(conf);

		ImageIO.setUseCache(false);

		Enumeration initParams = conf.getInitParameterNames();
		while (initParams.hasMoreElements()) {
			String key = (String) initParams.nextElement();
			String value = conf.getInitParameter(key);
			this.props.put(key, value);
		}

		Config config = new Config(this.props);
		this.kaptchaProducer = config.getProducerImpl();
		this.sessionKeyValue = config.getSessionKey();
	}

	public void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		resp.setDateHeader("Expires", 0L);

		resp.setHeader("Cache-Control", "no-store, no-cache, must-revalidate");

		resp.addHeader("Cache-Control", "post-check=0, pre-check=0");

		resp.setHeader("Pragma", "no-cache");

		resp.setContentType("image/jpeg");

		String capText = this.kaptchaProducer.createText();
		String s1 = capText.substring(0, 1);
		String s2 = capText.substring(1, 2);
		int r = Integer.valueOf(s1).intValue() + Integer.valueOf(s2).intValue();

		req.getSession().setAttribute(this.sessionKeyValue, String.valueOf(r));

		BufferedImage bi = this.kaptchaProducer.createImage(s1+"+"+s2+"=?");

		ServletOutputStream out = resp.getOutputStream();

		ImageIO.write(bi, "jpg", out);
		try {
			out.flush();
		} finally {
			out.close();
		}
	}
}