浅析Java验证码生成库JCaptcha

<dependency>      <groupId>com.octo.captcha</groupId>      <artifactId>jcaptcha</artifactId>      <version>1.0</version>    </dependency>

import com.octo.captcha.component.image.backgroundgenerator.BackgroundGenerator;import com.octo.captcha.component.image.backgroundgenerator.FileReaderRandomBackgroundGenerator;import com.octo.captcha.component.image.color.RandomListColorGenerator;import com.octo.captcha.component.image.fontgenerator.FontGenerator;import com.octo.captcha.component.image.fontgenerator.RandomFontGenerator;import com.octo.captcha.component.image.textpaster.DecoratedRandomTextPaster;import com.octo.captcha.component.image.textpaster.TextPaster;import com.octo.captcha.component.image.textpaster.textdecorator.TextDecorator;import com.octo.captcha.component.image.wordtoimage.ComposedWordToImage;import com.octo.captcha.component.image.wordtoimage.WordToImage;import com.octo.captcha.component.word.wordgenerator.RandomWordGenerator;import com.octo.captcha.component.word.wordgenerator.WordGenerator;import com.octo.captcha.engine.CaptchaEngine;import com.octo.captcha.engine.image.ListImageCaptchaEngine;import com.octo.captcha.image.gimpy.GimpyFactory;import java.awt.*;/** * 产生验证码图片的类 */public class CapchaHelper {  private static final Integer MIN_WORD_LENGTH = 4;// 验证码最小长度  private static final Integer MAX_WORD_LENGTH = 4;// 验证码最大长度  private static final Integer IMAGE_HEIGHT = 30;// 验证码图片高度  private static final Integer IMAGE_WIDTH = 130;// 验证码图片宽度  private static final Integer MIN_FONT_SIZE = 15;// 验证码最小字体  private static final Integer MAX_FONT_SIZE = 15;// 验证码最大字体  private static final String RANDOM_WORD = "0123456789";// 随机字符  // 验证码随机字体  private static final Font[] RANDOM_FONT = new Font[]{      new Font("nyala", Font.BOLD, MIN_FONT_SIZE),      new Font("Arial", Font.BOLD, MIN_FONT_SIZE),      new Font("Bell MT", Font.BOLD, MIN_FONT_SIZE),      new Font("Credit valley", Font.BOLD, MIN_FONT_SIZE),      new Font("Impact", Font.BOLD, MIN_FONT_SIZE)  };  // 验证码随机颜色  private static final Color[] RANDOM_COLOR = new Color[]{      new Color(255, 255, 255),      new Color(255, 220, 220),      new Color(220, 255, 255),      new Color(220, 220, 255),      new Color(255, 255, 220),      new Color(220, 255, 220)  };  private static ListImageCaptchaEngine captchaEngine;  public static CaptchaEngine getCaptchaEngine(final String imgPath) {    if (captchaEngine == null) {      synchronized (CapchaHelper.class) {        if (captchaEngine == null && imgPath != null) {          captchaEngine = new ListImageCaptchaEngine() {            @Override            protected void buildInitialFactories() {              RandomListColorGenerator randomListColorGenerator = new RandomListColorGenerator(RANDOM_COLOR);              BackgroundGenerator backgroundGenerator = new FileReaderRandomBackgroundGenerator(IMAGE_WIDTH, IMAGE_HEIGHT, imgPath);              WordGenerator wordGenerator = new RandomWordGenerator(RANDOM_WORD);              FontGenerator fontGenerator = new RandomFontGenerator(MIN_FONT_SIZE, MAX_FONT_SIZE, RANDOM_FONT);              TextDecorator[] textDecorator = new TextDecorator[]{};              TextPaster textPaster = new DecoratedRandomTextPaster(MIN_WORD_LENGTH, MAX_WORD_LENGTH, randomListColorGenerator, textDecorator);              WordToImage wordToImage = new ComposedWordToImage(fontGenerator, backgroundGenerator, textPaster);              addFactory(new GimpyFactory(wordGenerator, wordToImage));            }          };        }      }    }    return captchaEngine;  }}

//获取验证码背景图片的路径，这路径放了很多作为背景的图像    String captcha_backgrounds = session.getServletContext().getRealPath("/WEB-INF/img/captcha");    CaptchaEngine ce = CapchaHelper.getCaptchaEngine(captcha_backgrounds);    //需要admin网页中用js定时从服务端获取当前的验证码    Captcha captcha = ce.getNextCaptcha();    //为了验证，把captcha对象放到session中，以在客户端提交验证码时进行验证    req.getSession().setAttribute("captcha", captcha);    //获取验证码图片，这是未压缩的位图    BufferedImage image = (BufferedImage) captcha.getChallenge();    resp.setContentType("image/jpeg");    ImageIO.write(image, "jpg", resp.getOutputStream());

//获取验证码背景图片的路径，这路径放了很多作为背景的图像    String captcha_backgrounds = session.getServletContext().getRealPath("/WEB-INF/img/captcha");    CaptchaEngine ce = CapchaHelper.getCaptchaEngine(captcha_backgrounds);    //需要admin网页中用js定时从服务端获取当前的验证码    Captcha captcha = ce.getNextCaptcha();    //为了验证，把captcha对象放到session中，以在客户端提交验证码时进行验证    session.setAttribute("captcha", captcha);    //获取验证码图片，这是未压缩的位图    BufferedImage image = (BufferedImage) captcha.getChallenge();    ByteArrayOutputStream bao=new ByteArrayOutputStream();    //应缩成jpg并写到输出流中    ImageIO.write(image, "jpg", bao);    return bao.toByteArray();

<img id="captcha" src="/captcha_img" onclick="refreshCaptchaImg()" />

function refreshCaptchaImg() {      //从服务端重新下载验证码图片      //给这个地加参数纯为了强制刷新，否则由于src指向的url地址没变,浏览器不会真正生刷新图片      var now = new Date()      $("#captcha").attr("src","/captcha_img?"+now.getTime());