使用 jcaptcha 产生图片校验码

具体使用的例子： www.tongriben.com

第一步：下载 jcaptcha-all-1.0-RC2.0.1.jar
第二步：代码实现
CaptchaServiceSingleton.java

 
package com.yh.web.jcaptcha;

import java.awt.Color;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Iterator;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import org.apache.log4j.Logger;

import com.octo.captcha.component.image.backgroundgenerator.BackgroundGenerator;
import com.octo.captcha.component.image.backgroundgenerator.GradientBackgroundGenerator;
import com.octo.captcha.component.image.fontgenerator.FontGenerator;
import com.octo.captcha.component.image.fontgenerator.RandomFontGenerator;
import com.octo.captcha.component.image.textpaster.RandomTextPaster;
import com.octo.captcha.component.image.textpaster.SimpleTextPaster;
import com.octo.captcha.component.image.textpaster.TextPaster;
import com.octo.captcha.component.image.wordtoimage.ComposedWordToImage;
import com.octo.captcha.component.image.wordtoimage.WordToImage;
import com.octo.captcha.component.wordgenerator.RandomWordGenerator;
import com.octo.captcha.component.wordgenerator.WordGenerator;
import com.octo.captcha.engine.image.ListImageCaptchaEngine;
import com.octo.captcha.image.ImageCaptcha;
import com.octo.captcha.image.ImageCaptchaFactory;
import com.octo.captcha.image.gimpy.GimpyFactory;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class CaptchaServiceSingleton extends ListImageCaptchaEngine {
	private static Logger log = Logger.getLogger(CaptchaServiceSingleton.class);

	private static final Integer MIN_WORD_LENGTH = new Integer(4);

	private static final Integer MAX_WORD_LENGTH = new Integer(6);

	private static final Integer IMAGE_WIDTH = new Integer(70);

	private static final Integer IMAGE_HEIGHT = new Integer(20);

	private static final Integer MIN_FONT_SIZE = new Integer(12);

	private static final Integer MAX_FONT_SIZE = new Integer(14);

	private static final String NUMERIC_CHARS = "23456789";// No numeric 0

	private static final String UPPER_ASCII_CHARS = "ABCDEFGHJKLMNPQRSTXYZ";// No

	// upper
	// O I

	// we dont use the lower characters because it cause dificult in some case,
	// so that
	// we must always UPPERCASE the input from user (currently in
	// OnlineUserImpl)
	private static final String LOWER_ASCII_CHARS = "abcdefghjkmnpqrstxyz";// No

	// lower
	// o i

	/**
	 * Singleton instance of this class
	 */
	private static CaptchaServiceSingleton instance = new CaptchaServiceSingleton();

	private ArrayList textPasterList;

	private ArrayList backgroundGeneratorList;

	private ArrayList fontGeneratorList;

	ImageCaptcha imageCaptcha = null;

	/**
	 * Private constructor to prevent instantiation
	 */
	private CaptchaServiceSingleton() {
	}

	public static CaptchaServiceSingleton getInstance() {
		return instance;
	}

	protected void buildInitialFactories() {
		try {
			textPasterList = new ArrayList();
			backgroundGeneratorList = new ArrayList();
			fontGeneratorList = new ArrayList();

			textPasterList.add(new SimpleTextPaster(MIN_WORD_LENGTH,
					MAX_WORD_LENGTH, Color.black));
			textPasterList.add(new RandomTextPaster(MIN_WORD_LENGTH,
					MAX_WORD_LENGTH, Color.black));
			textPasterList.add(new SimpleTextPaster(MIN_WORD_LENGTH,
					MAX_WORD_LENGTH, Color.black));
			textPasterList.add(new RandomTextPaster(MIN_WORD_LENGTH,
					MAX_WORD_LENGTH, Color.black));
			textPasterList.add(new SimpleTextPaster(MIN_WORD_LENGTH,
					MAX_WORD_LENGTH, Color.blue));
			textPasterList.add(new RandomTextPaster(MIN_WORD_LENGTH,
					MAX_WORD_LENGTH, Color.blue));

			backgroundGeneratorList.add(new GradientBackgroundGenerator(
					IMAGE_WIDTH, IMAGE_HEIGHT, Color.orange, Color.white));
			backgroundGeneratorList.add(new GradientBackgroundGenerator(
					IMAGE_WIDTH, IMAGE_HEIGHT, Color.white, Color.green));
			backgroundGeneratorList.add(new GradientBackgroundGenerator(
					IMAGE_WIDTH, IMAGE_HEIGHT, Color.gray, Color.white));
			backgroundGeneratorList.add(new GradientBackgroundGenerator(
					IMAGE_WIDTH, IMAGE_HEIGHT, Color.white, Color.orange));
			backgroundGeneratorList.add(new GradientBackgroundGenerator(
					IMAGE_WIDTH, IMAGE_HEIGHT, Color.green, Color.white));
			backgroundGeneratorList.add(new GradientBackgroundGenerator(
					IMAGE_WIDTH, IMAGE_HEIGHT, Color.yellow, Color.white));
			backgroundGeneratorList.add(new GradientBackgroundGenerator(
					IMAGE_WIDTH, IMAGE_HEIGHT, Color.white, Color.magenta));

			

			// fontGeneratorList.add(new
			// TwistedAndShearedRandomFontGenerator(MIN_FONT_SIZE,
			// MAX_FONT_SIZE));
			// fontGeneratorList.add(new
			// TwistedRandomFontGenerator(MIN_FONT_SIZE, MAX_FONT_SIZE));// link
			// character too much
			fontGeneratorList.add(new RandomFontGenerator(MIN_FONT_SIZE,
					MAX_FONT_SIZE));// to easy to read
			// fontGeneratorList.add(new
			// DeformedRandomFontGenerator(MIN_FONT_SIZE, MAX_FONT_SIZE));// to
			// small font

			// no char upper O, char lower o and numerric 0 because user cannot
			// answer
			WordGenerator words = new RandomWordGenerator(NUMERIC_CHARS
					+ UPPER_ASCII_CHARS);

			for (Iterator fontIter = fontGeneratorList.iterator(); fontIter
					.hasNext();) {
				FontGenerator font = (FontGenerator) fontIter.next();
				for (Iterator backIter = backgroundGeneratorList.iterator(); backIter
						.hasNext();) {
					BackgroundGenerator back = (BackgroundGenerator) backIter
							.next();
					for (Iterator textIter = textPasterList.iterator(); textIter
							.hasNext();) {
						TextPaster parser = (TextPaster) textIter.next();

						WordToImage word2image = new ComposedWordToImage(font,
								back, parser);
						ImageCaptchaFactory factory = new GimpyFactory(words,
								word2image);
						addFactory(factory);
					}
				}
			}
		} catch (Exception ex) {
			log.error("产生校验码初始化异常 ＝＝ " + ex);
			// throw ex;
		}
	}

	/**
	 * Write the captcha image of current user to the servlet response
	 * 
	 * @param request
	 *            HttpServletRequest
	 * @param response
	 *            HttpServletResponse
	 * @throws IOException
	 */
	public void writeCaptchaImage(HttpServletRequest request,
			HttpServletResponse response) throws IOException {

		imageCaptcha = getNextImageCaptcha();
		HttpSession session = request.getSession();
		session.setAttribute("imageCaptcha", imageCaptcha);
		BufferedImage image = (BufferedImage) imageCaptcha.getChallenge();

		OutputStream outputStream = null;
		try {
			outputStream = response.getOutputStream();
			// render the captcha challenge as a JPEG image in the response
			response.setHeader("Cache-Control", "no-store");
			response.setHeader("Pragma", "no-cache");
			response.setDateHeader("Expires", 0);

			response.setContentType("image/jpeg");

			JPEGImageEncoder encoder = JPEGCodec
					.createJPEGEncoder(outputStream);
			encoder.encode(image);

			outputStream.flush();
			outputStream.close();
			outputStream = null;// no close twice
		} catch (IOException ex) {
			log.error("产生图片异常 ＝＝ " + ex);
			throw ex;
		} finally {
			if (outputStream != null) {
				try {
					outputStream.close();
				} catch (IOException ex) {
				}
			}
			imageCaptcha.disposeChallenge();
		}
	}

	public boolean validateCaptchaResponse(String validateCode,
			HttpSession session) {
		boolean flag = true;
		try {
			imageCaptcha = (ImageCaptcha) session.getAttribute("imageCaptcha");
			if (imageCaptcha == null) {
				// log.info("validateCaptchaResponse returned false due to
				// imageCaptcha is null");
				flag = false;
			}
			//validateCode = validateCode.toLowerCase();// use upper case for
			validateCode = validateCode.toUpperCase();// use upper case for
			// easier usage
flag = (imageCaptcha.validateResponse(validateCode)).booleanValue();
			session.removeAttribute("imageCaptcha");
			return flag;
		} catch (Exception ex) {
			ex.printStackTrace();
			log.error("校验码校验异常 ＝＝ " + ex);
			return false;
		}
	}
	
}

ImageCaptchaServlet.java

 
package com.yh.web.servlet;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.yh.web.jcaptcha.CaptchaServiceSingleton;
import com.octo.captcha.service.CaptchaServiceException;

public class ImageCaptchaServlet extends HttpServlet {

	private static final long serialVersionUID = -5382766069139170499L;
	public void init(ServletConfig servletConfig) throws ServletException {

		super.init(servletConfig);

	}

	protected void doGet(HttpServletRequest httpServletRequest,
			HttpServletResponse httpServletResponse) throws ServletException,
			IOException {
		System.out.println("---------- ImageCaptchaServlet pass here -------------");
		try {
			CaptchaServiceSingleton.getInstance().writeCaptchaImage(
					httpServletRequest, httpServletResponse);

		} catch (IllegalArgumentException e) {
			httpServletResponse.sendError(HttpServletResponse.SC_NOT_FOUND);
			return;
		} catch (CaptchaServiceException e) {
			httpServletResponse
					.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
			return;
		}
	}
}

jsp页面增加校验码内容:
<tr><td>
校验码：<input type="text" size="8" name="checkCode" id="checkCode" class="normal_input"/><img src="/jcaptcha" id="checkCodeImg" onclick="this.src='/jcaptcha?now=' + new Date().getTime()" alt="看不清，点击换一张" >请输入校验码，大小写不区分<br> 如看不清，请点击图片换一张
</td></tr>
判断校验码是否正确的java代码：

HttpSession session = request.getSession();   
boolean isResponseCorrect = false;   
// retrieve the response   
String validateCode = checkCode.trim();   
System.out.println("checkCode == "  
        + checkCode);   
try {   
    isResponseCorrect = CaptchaServiceSingleton.getInstance()   
            .validateCaptchaResponse(validateCode, session);   
  
    return isResponseCorrect;   
} catch (Exception e) {   
    // should not happen, may be thrown if the id is not valid   
  
    return false;   
}