Installing

The process for installing SimpleCaptcha is no different than installing most other libraries for a J2EE container: a jar is deployed to WEB-INF/lib and web.xml is updated. These steps are described for reference below.

  1. Download SimpleCaptcha
  2. Copy the SimpleCaptcha jar file to your WEB-INF/lib directory
  3. Add servlet mappings to web.xml. Four servlets are provided for you: StickyCaptchaServlet, SimpleCaptchaServlet, ChineseCaptchaServlet, and AudioCaptchaServlet. All generate CAPTCHA challenge/answer pairs, but StickyCaptchaServlet and ChineseCaptchaServlet are “sticky” to the user’s session: page reloads will render the same CAPTCHA instead of generating a new one. An example mapping for StickyCaptchaServlet:
    <servlet>
        <servlet-name>StickyCaptcha</servlet-name>
        <servlet-class>nl.captcha.servlet.StickyCaptchaServlet</servlet-class>
        <!-- The width and height params are optional; 
        if unspecified they default to 200 and 50 respectively. --!>
        <init-param>
            <param-name>width</param-name>
            <param-value>250</param-value>
        </init-param>
        <init-param>
            <param-name>height</param-name>
            <param-value>75</param-value>
        </init-param>
    </servlet>

    <servlet-mapping>
        <servlet-name>StickyCaptcha</servlet-name>
        <url-pattern>/stickyImg</url-pattern>
    </servlet-mapping>

And for AudioCaptchaServlet:

    <servlet>
        <servlet-name>AudioCaptcha</servlet-name>
        <servlet-class>nl.captcha.servlet.AudioCaptchaServlet</servlet-class>
    </servlet>

     <servlet-mapping>
        <servlet-name>AudioCaptcha</servlet-name>
        <url-pattern>/audio.wav</url-pattern>
    </servlet-mapping>
  1. Restart your webserver.
  2. Browse to one of the locations given by the url-patterns defined in web.xml, e.g., http://localhost:8080/stickyImg. If everything has been set up correctly you should see/hear a CAPTCHA challenge.
  3. Now create a JSP called captcha.jsp. For an image CAPTCHA, add the following code inside the <body> element:
    <img src="/stickyImg" />
    <form action="/captchaSubmit.jsp" method="post">
        <input name="answer" />
    </form>

Or for an audio CAPTCHA:

    <audio controls autoplay src="/audio.wav"></audio>
    <form action="/captchaSubmit.jsp" method="post">
        <input name="answer" />
    </form>
  1. Create another JSP called captchaSubmit.jsp. Add the following:
    <%@ page import="nl.captcha.Captcha" %>
    ...
    <% // We're doing this in a JSP here, but in your own app you'll want to put
    // this logic in your MVC framework of choice.
    Captcha captcha = (Captcha) session.getAttribute(Captcha.NAME);
    // Or, for an AudioCaptcha:
    // AudioCaptcha captcha = (AudioCaptcha) session.getAttribute(Captcha.NAME);
    request.setCharacterEncoding("UTF-8"); // Do this so we can capture non-Latin chars
    String answer = request.getParameter("answer");
    if (captcha.isCorrect(answer)) { %>
        <b>Correct!</b>
    <% } %>
  1. Browse to /captcha.jsp. You should get your CAPTCHA image, as well as a form for entering your answer. Submit the form and see what happens.

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