<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>
（十六）背景渐变颜色
<init-param> <description>背景颜色渐变，开始颜色</description> <param-name>kaptcha.background.clear.from</param-name> <param-value>green</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>
（十七）文字渲染器
<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>
（十八）图片的验证码会保存在Session中，其中的值为
<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>
（十九）图片实现类别
<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>
（二十）文本实现类（可通过重写该类来实现验证码为中文）
<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>
重写文本实现类，实现验证码为中文：
1.创建一个类别，继承Configurable 实现TextProducer（在jar包中）
import com.google.code.kaptcha.text.TextProducer; import com.google.code.kaptcha.util.Configurable; import java.util.Random; 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" }; 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; // 前闭后开[11,14) 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; } }
2.修改Web.xml配置
<init-param> <description>文本实现类</description> <param-name>kaptcha.textproducer.impl</param-name> <param-value> ChineseText </param-value> </init-param> 五、验证码的校验（本文是利用check.jsp来校验的）保存在Session中，其中的键值为（第十八个属性） [html] view plain copy <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"); if (k.equals(str)) out.print("true"); out.print(k + "---" + str); %> </body>
六、扩展（加法验证码的实现）
1.重写KaptchaServlet类
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; import javax.servlet.http.HttpSession; 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(); } } }
2.修改配置文件
<servlet> <servlet-name>Kaptcha</servlet-name> <servlet-class>KaptchaServlet</servlet-class> </servlet>