java 验证码生成

 import java.awt.Color;
 import java.awt.Font;
 import java.io.IOException;
 import java.io.OutputStream;
 import java.util.ArrayList;
 import java.util.List;

 import javax.imageio.ImageIO;
 import javax.servlet.Servlet;
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;

 import org.apache.commons.lang.math.RandomUtils;

 import nl.captcha.Captcha;
 import nl.captcha.Captcha.Builder;
 import nl.captcha.gimpy.BlockGimpyRenderer;
 import nl.captcha.text.producer.ChineseTextProducer;
 import nl.captcha.text.producer.DefaultTextProducer;
 import nl.captcha.text.renderer.DefaultWordRenderer;
 import nl.captcha.text.renderer.WordRenderer;

 public class CaptchaServlet extends HttpServlet implements Servlet {
     private static final long serialVersionUID = 1L;
     private static final String PARAM_HEIGHT = "height"; // 高度 默认为50

     private static final String PARAM_WIDTH = "width";// 宽度 默认为200

     private static final String PAEAM_NOISE = "noise";// 干扰线条 默认是没有干扰线条

     private static final String PAEAM_TEXT = "text";// 文本

     protected int _width = 150;
     protected int _height = 40;
     protected boolean _noise = false;
     protected String _text = "number:1,word:1,number:1,number:1,word:1";

     /**
      * 初始化过滤器.将配置文件的参数文件赋值
      *
      * @throws ServletException
      */
     @Override
     public void init() throws ServletException {
         if (getInitParameter(PARAM_HEIGHT) != null) {
             _height = Integer.valueOf(getInitParameter(PARAM_HEIGHT));
         }

         if (getInitParameter(PARAM_WIDTH) != null) {
             _width = Integer.valueOf(getInitParameter(PARAM_WIDTH));
         }

         if (getInitParameter(PAEAM_NOISE) != null) {
             _noise = Boolean.valueOf(getInitParameter(PAEAM_NOISE));
         }

         if (getInitParameter(PAEAM_NOISE) != null) {
             _text = String.valueOf(getInitParameter(PAEAM_TEXT));
         }
     }

     /**
      * 因为获取图片只会有get方法
      */
     @Override
     public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

         Builder builder = new Captcha.Builder(_width, _height);
         // 增加边框
         // builder.addBorder();
         // 是否增加干扰线条
         if (_noise == true) {
             builder.addNoise();
         }
         // ----------------自定义字体大小-----------
         // 自定义设置字体颜色和大小 最简单的效果 多种字体随机显示
         List<Font> fontList = new ArrayList<Font>();
         fontList.add(new Font("微软 雅黑", Font.LAYOUT_NO_START_CONTEXT, 30));// 可以设置斜体之类的
         DefaultWordRenderer dwr = new DefaultWordRenderer(getRandomColor(), fontList);
         // 加入多种颜色后会随机显示 字体空心

         WordRenderer wr = dwr;
         // 增加文本，默认为5个随机字符.
         if (_text == null) {
             builder.addText();
         } else {
             String[] ts = _text.split(",");
             for (int i = 0; i < ts.length; i++) {
                 String[] ts1 = ts[i].split(":");
                 if ("chinese".equals(ts1[0])) {
                     builder.addText(new ChineseTextProducer(Integer.parseInt(ts1[1])), wr);
                 } else if ("number".equals(ts1[0])) {
                     // 这里没有0和1是为了避免歧义 和字母I和O
                     char[] numberChar = new char[] { '2', '3', '4', '5', '6', '7', '8' };
                     builder.addText(new DefaultTextProducer(Integer.parseInt(ts1[1]), numberChar), wr);
                 } else if ("word".equals(ts1[0])) {
                     // 原理同上
                     char[] numberChar = new char[] { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'k', 'm', 'n', 'p', 'r',
                             'w', 'x', 'y' };
                     builder.addText(new DefaultTextProducer(Integer.parseInt(ts1[1]), numberChar), wr);
                 } else {
                     builder.addText(new DefaultTextProducer(Integer.parseInt(ts1[1])), wr);
                 }
             }

         }

         // --------------添加背景-------------
         // 设置背景渐进效果 以及颜色 form为开始颜色，to为结束颜色
         // GradiatedBackgroundProducer gbp=new GradiatedBackgroundProducer();
         // gbp.setFromColor(Color.yellow);
         // gbp.setToColor(Color.red);
         // 无渐进效果，只是填充背景颜色
         // FlatColorBackgroundProducer fbp=new
         // FlatColorBackgroundProducer(Color.red);
         // 加入网纹--一般不会用
         // SquigglesBackgroundProducer sbp=new SquigglesBackgroundProducer();
         // 没发现有什么用,可能就是默认的
         // TransparentBackgroundProducer tbp = new
         // TransparentBackgroundProducer();

         // builder.addBackground(gbp);
         // ---------装饰字体---------------
         // 字体边框齿轮效果 默认是3
         builder.gimp(new BlockGimpyRenderer(1));
         // 波纹渲染 相当于加粗
         // builder.gimp(new RippleGimpyRenderer());
         // 修剪--一般不会用
         // builder.gimp(new ShearGimpyRenderer(Color.red));
         // 加网--第一个参数是横线颜色，第二个参数是竖线颜色
         // builder.gimp(new FishEyeGimpyRenderer(Color.red,Color.yellow));
         // 加入阴影效果 默认3，75
         // builder.gimp(new DropShadowGimpyRenderer());
         // 创建对象
         Captcha captcha = builder.build();

         req.getSession().setAttribute("simpleCaptcha", captcha);
         resp.setHeader("Cache-Control", "private,no-cache,no-store");
         resp.setContentType("image/png");
         try {
             OutputStream os = resp.getOutputStream();
             ImageIO.write(captcha.getImage(), "png", os);
             os.close();
         } catch (IOException e) {
             e.printStackTrace();
         }
     }

     public Color getRandomColor() {
         int n = RandomUtils.nextInt(100);

         if (n % 3 == 1) {
             return Color.RED;
         } else if (n % 3 == 2) {
             return Color.BLUE;
         }
         return Color.GREEN;
     }
 }