Patchca验证码插件简单而功能强大

<servlet>
    <servlet-name>patchca</servlet-name>
    <servlet-class>com.ssh.servlet.CaptchaServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>patchca</servlet-name>
    <url-pattern>/patchca.png</url-pattern>
</servlet-mapping>

public class CaptchaServlet extends HttpServlet {
    private static final long serialVersionUID = 4968328161261528097L;
    private static MyCaptchaService cs = null;
    @Override
    public void init() throws ServletException {
        super.init();
        //可直接使用ConfigurableCaptchaService，然后修改配置
        cs = new MyCaptchaService();
    }
    @Override
    public void destroy() {
        cs = null;
        super.destroy();
    }
    public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
        response.setContentType("image/png");
        response.setHeader("cache", "no-cache");
        HttpSession session = request.getSession(true);
        OutputStream os = response.getOutputStream();
        String patchca= EncoderHelper.getChallangeAndWriteImage(cs, "png", os);
        session.setAttribute("PATCHCA", patchca);
        os.flush();
        os.close();
    }
    public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
        this.doGet(request, response);
    }
    private class MyCaptchaService extends AbstractCaptchaService {
        public MyCaptchaService() {
            //文本内容
            wordFactory = new MyWordFactory();
            //字体
            fontFactory = new RandomFontFactory();
            //效果
            textRenderer = new BestFitTextRenderer();
            //背景
            backgroundFactory = new SingleColorBackgroundFactory();
            //字体颜色
            colorFactory = new SingleColorFactory(new Color(25, 60, 170));
            //样式(曲线波纹加干扰线)
            filterFactory = new CurvesRippleFilterFactory(colorFactory);
            //图片长宽
            width = 150;
            height = 50;
        }
    }
    private class MyWordFactory extends RandomWordFactory {
        public MyWordFactory() {
            //文本范围和长度
            characters = "absdekmnowx23456789";
            minLength = 5;
            maxLength = 4;
        }
    }
}

包中提供的配置：

ConfigurableCaptchaService：

FontFactory 字体
    默认：RandomFontFactory（Verdana，Tahoma，minSize、maxSize=45）
WordFactory 单词范围和长度
    默认：RandomWordFactory 单词6-6
    其他：AdaptiveRandomWordFactory 自适应(mw字母宽度加长)
ColorFactory
    默认：SingleColorFactory 黑色
BackgroundFactory
    默认：SingleColorBackgroundFactory 白色
TextRenderer 文本渲染
    默认：BestFitTextRenderer
FilterFactory 样式
    默认：CurvesRippleFilterFactory（曲线波纹带干扰线，干扰线颜色为当前colorFactory）
width/height 图片长宽
    默认：160*70

public class CaptchaServlet extends HttpServlet {
    private static final long serialVersionUID = 4968328161261528097L;
    private static ConfigurableCaptchaService cs = null;
    private static ColorFactory cf = null;
    private static RandomWordFactory wf = null;
    private static Random r = new Random();
    private static CurvesRippleFilterFactory crff = null;
    private static MarbleRippleFilterFactory mrff = null;
    private static DoubleRippleFilterFactory drff = null;
    private static WobbleRippleFilterFactory wrff = null;
    private static DiffuseRippleFilterFactory dirff = null;
    @Override
    public void init() throws ServletException {
	    super.init();
	    cs = new ConfigurableCaptchaService();
	    cf = new SingleColorFactory(new Color(25, 60, 170));
	    wf = new RandomWordFactory();
	    crff = new CurvesRippleFilterFactory(cs.getColorFactory());
	    drff = new DoubleRippleFilterFactory();
	    wrff = new WobbleRippleFilterFactory();
	    dirff = new DiffuseRippleFilterFactory();
	    mrff = new MarbleRippleFilterFactory();
	    cs.setWordFactory(wf);
	    cs.setColorFactory(cf);
	    cs.setWidth(120);
	    cs.setHeight(50);
    }
    @Override
    public void destroy() {
	    wf = null;
	    cf = null;
	    cs = null;
	    super.destroy();
    }
    public void doGet(HttpServletRequest request, HttpServletResponse response)
	        throws ServletException, IOException {
	    response.setContentType("image/png");
	    response.setHeader("cache", "no-cache");
	    wf.setMaxLength(5);
	    wf.setMinLength(3);
	    HttpSession session = request.getSession(true);
	    OutputStream os = response.getOutputStream();
            //随机产生5种效果（filter）
	    switch (r.nextInt(5)) {
	    case 0:
		    cs.setFilterFactory(crff);
		    break;
	    case 1:
		    cs.setFilterFactory(mrff);
		    break;
	    case 2:
		    cs.setFilterFactory(drff);
		    break;
	    case 3:
		    cs.setFilterFactory(wrff);
		    break;
	    case 4:
		    cs.setFilterFactory(dirff);
		    break;
	    }
	    String patchca= EncoderHelper.getChallangeAndWriteImage(cs, "png", os);
	    session.setAttribute("PATCHCA", patchca);
	    os.flush();
	    os.close();
	}
}

SimpleCaptchaService(int width, int height, Color textColor,  Color backgroundColor, int fontSize, String[]fontNames, FilterFactory ff) {
    backgroundFactory = new SingleColorBackgroundFactory(backgroundColor);
    wordFactory = new AdaptiveRandomWordFactory();
    fontFactory = new RandomFontFactory(fontNames);
    textRenderer = new BestFitTextRenderer();
    colorFactory = new SingleColorFactory(textColor);
    filterFactory = ff;
    this.width = width;
    this.height = height;
}

<table>
    <tr>
        <!-- patchca.png和servlet中的<url-pattern>对应 -->
        <td><img src="patchca.png" alt="验证码"  style="cursor:pointer;vertical-align:text-bottom;" onclick="this.src=this.src+'?'+Math.random();"></td>
		<td valign="top">
			<form method="POST">
				<br> 验证码:<input type="text" name="patchcafield"><br />
				<input type="submit" name="submit">
			</form>
		</td>
	</tr>
</table>

<%
    //"PATCHCA"和servlet中定义的session保存位置对应
    String c = (String)session.getAttribute("PATCHCA");
    String parm = (String) request.getParameter("patchcafield");
    out.println("Parameter: " + parm + " ? Session Key: " + c + " : ");
    if (c != null && parm != null) {
        if (c.equalsIgnoreCase(parm)) {
            out.println("<b>true</b>");
        } else {
            out.println("<b>false</b>");
        }
    }
%>