in the ImageCaptchaServlet.java :

when execute bellow code :

CaptchaServiceSingleton.getInstance().getImageChallengeForID(captchaId, request.getLocale());

web server occur exception :

Exception.java.lang.NoClassDefFoundError
        at com.chtd.dsis.alf.ImageCaptchaServlet.doGet(ImageCaptchaServlet.java:35)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
        at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run(ServletStubImpl.java:1077)
        at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:465)
        at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:348)
        at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:7047)
        at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
        at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:121)
        at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3902)
        at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2773)
        at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:224)
        at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:183)