1.从官网下载插件。将对应jar包导入到lib文件夹下
2.创建一个CaptchaServiceSingleton类用来获取jcaptcha自己实现的默认验证码生成器对象DefaultManageableImageCaptchaService（使用单例模式）。
package com.xhc.jcaptcha;import com.octo.captcha.service.image.DefaultManageableImageCaptchaService;import com.octo.captcha.service.image.ImageCaptchaService;public class CaptchaServiceSingleton { private static ImageCaptchaService instance = new DefaultManageableImageCaptchaService(); public static ImageCaptchaService getInstance(){ return instance; }} 3.创建处理验证码生成的servlet
package com.xhc.jcaptcha;import java.awt.image.BufferedImage;import java.awt.image.Raster;import java.io.ByteArrayOutputStream;import java.io.IOException;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 com.octo.captcha.service.CaptchaServiceException;import com.sun.image.codec.jpeg.JPEGCodec;import com.sun.image.codec.jpeg.JPEGImageEncoder;public class ImageCaptchaServlet extends HttpServlet { public void destroy() { super.destroy(); } public void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws ServletException, IOException { byte[] captchaChallengeAsJpeg = null; // the output stream to render the captcha image as jpeg into ByteArrayOutputStream jpegOutputStream = new ByteArrayOutputStream(); try { // get the session id that will identify the generated captcha. //the same id must be used to validate the response, the session id is a good candidate! String captchaId = httpServletRequest.getSession().getId(); // call the ImageCaptchaService getChallenge method BufferedImage challenge = new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB); challenge=CaptchaServiceSingleton.getInstance().getImageChallengeForID(captchaId, httpServletRequest.getLocale()); // a jpeg encoder JPEGImageEncoder jpegEncoder = JPEGCodec.createJPEGEncoder(jpegOutputStream); jpegEncoder.encode(challenge); } catch (IllegalArgumentException e) { httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND); return; } catch (CaptchaServiceException e) { httpServletResponse.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR); return; } captchaChallengeAsJpeg = jpegOutputStream.toByteArray(); // flush it in the response httpServletResponse.setHeader("Cache-Control", "no-store"); httpServletResponse.setHeader("Pragma", "no-cache"); httpServletResponse.setDateHeader("Expires", 0); httpServletResponse.setContentType("image/jpeg"); ServletOutputStream responseOutputStream = httpServletResponse.getOutputStream(); responseOutputStream.write(captchaChallengeAsJpeg); responseOutputStream.flush(); responseOutputStream.close(); } public void init(ServletConfig servletConfig) throws ServletException { super.init(servletConfig); }} 若导入这两个类时报错
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;
原因：Eclipse默认把这些受訪问限制的API设成了ERROR。
仅仅要把Windows-Preferences-Java-Complicer-Errors/Warnings里面的Deprecated and restricted API中的Forbidden references(access rules)选为Warning就能够编译通过。
4.创建用来做验证的servlet
package com.xhc.jcaptcha;import java.io.IOException;import java.io.PrintWriter;import java.net.HttpRetryException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import com.octo.captcha.service.CaptchaServiceException;public class ValidationServlet extends HttpServlet { public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } public void doGet(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws ServletException, IOException { Boolean isResponseCorrect =Boolean.FALSE; //remenber that we need an id to validate! String captchaId = httpServletRequest.getSession().getId(); //retrieve the response String response = httpServletRequest.getParameter("j_captcha_response"); // Call the Service method httpServletResponse.setContentType("text/html;charset=utf-8"); PrintWriter wt=httpServletResponse.getWriter(); try { isResponseCorrect = CaptchaServiceSingleton.getInstance().validateResponseForID(captchaId, response); if(isResponseCorrect){ wt.write("验证码输入成功"); }else{ wt.write("验证码输入失败"); } } catch (CaptchaServiceException e) { //should not happen, may be thrown if the id is not valid } } public void init() throws ServletException { }} 5.配置web.xml
ImageCaptchaServlet com.xhc.jcaptcha.ImageCaptchaServlet 0 ValidationServlet com.xhc.jcaptcha.ValidationServlet ImageCaptchaServlet /servlet/ImageCaptchaServlet ValidationServlet /servlet/ValidationServlet
6.jsp页面