kaptcha实现算式验证码

1.新建一个Dynamic Web Project项目，里面新建一个servlet文件，还有两个jsp文件和一个xml文件，在lib里面加入要用到的jar包，然后导入。整体的框架图如下所示：

2.KaptchaServlet.java里面的代码如下所示：

import com.google.code.kaptcha.Producer;
import com.google.code.kaptcha.util.Config;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Properties;
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;

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();
		}
	}
}

3.index.jsp里面的代码如下图所示：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>









	

	

		
		
	
	

4.check.jsp里面的代码如下所示：

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>







	<%
		String k = (String) session.getAttribute(com.google.code.kaptcha.Constants.KAPTCHA_SESSION_KEY);
		String str = request.getParameter("r");
		if (k.equals(str)){
			out.print("验证成功！
");
		}else{
			out.print("验证失败！
");
		}
		out.print("正确的结果是：" + k + "
");
		out.print("你输入的结果是：" + str + "
");
	%>

5.web.xml里面的代码如下所示：

	
	
		Kaptcha
		
			KaptchaServlet
		
		
			图片边框，合法值：yes , no
			kaptcha.border
			yes
		
		
			
				边框颜色，合法值： r,g,b (and optional alpha) 或者
				white,black,blue.
			
			kaptcha.border.color
			black
		
		
			边框厚度，合法值：>0
			kaptcha.border.thickness
			1
		
		
			图片宽 200
			kaptcha.image.width
			200
		
		
			图片高 50
			kaptcha.image.height
			50
		
		
			图片实现类
			kaptcha.producer.impl
			
				com.google.code.kaptcha.impl.DefaultKaptcha
			
		
		
			文本实现类
			kaptcha.textproducer.impl
			
				com.google.code.kaptcha.text.impl.DefaultTextCreator
			
		
		
			文本集合，验证码值从此集合中获取
			kaptcha.textproducer.char.string
			1234567890
			
			
		
		
			验证码长度 5
			kaptcha.textproducer.char.length
			2
		
		
			字体 Arial, Courier
			kaptcha.textproducer.font.names
			Arial, Courier
		
		
			字体大小 40px.
			kaptcha.textproducer.font.size
			40
		
		
			
				字体颜色，合法值： r,g,b 或者 white,black,blue.
			
			kaptcha.textproducer.font.color
			black
		
		
			文字间隔 2
			kaptcha.textproducer.char.space
			2
		
		
			干扰实现类
			kaptcha.noise.impl
			
				
				com.google.code.kaptcha.impl.DefaultNoise
			
		
		
			
				干扰颜色，合法值： r,g,b 或者 white,black,blue.
			
			kaptcha.noise.color
			black
		
		
			
				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
			
			kaptcha.obscurificator.impl
			
				com.google.code.kaptcha.impl.WaterRipple
			
		
		
			背景实现类
			kaptcha.background.impl
			
				com.google.code.kaptcha.impl.DefaultBackground
			
		
		
			背景颜色渐变，开始颜色
			kaptcha.background.clear.from
			green
		
		
			背景颜色渐变，结束颜色
			kaptcha.background.clear.to
			white
		
		
			文字渲染器
			kaptcha.word.impl
			
				com.google.code.kaptcha.text.impl.DefaultWordRenderer
			
		
		
			
				session中存放验证码的key键
			
			kaptcha.session.key
			KAPTCHA_SESSION_KEY
		
		
			
				The date the kaptcha is generated is put into the
				HttpSession. This is the key value for that item in the
				session.
			
			kaptcha.session.date
			KAPTCHA_SESSION_DATE
		
	
	
		Kaptcha
		/randomcode.jpg
	


	
		index.jsp
	

6.在浏览器里面输入http://localhost:8080/KaptchaCode/index.jsp运行得到如下的结果：