单点登录加验证码例子

     在部署cas登录过程中,可能会用到验证码功能,这里简要介绍一下加入验证码的过程.
1.   首先,我用的cas版本是3.4.6,验证码采用的是CAPTCHA,所需jar包可以google搜索,部署好cas后.在web-info目录下找到login-webflow.xml,打开,找到如下代码:
     <view-state id="viewLoginForm" view="casLoginView" model="credentials">
        <var name="credentials" class="org.jasig.cas.authentication.principal.UsernamePasswordCredentials" />
        <binder>
            <binding property="username" />
            <binding property="password" />
        </binder>
        <on-entry>
            <set name="viewScope.commandName" value="'credentials'" />
        </on-entry>
<transition on="submit" bind="true" validate="true" to="realSubmit">
            <set name="flowScope.credentials" value="credentials" />
            <evaluate expression="authenticationViaFormAction.doBind(flowRequestContext, flowScope.credentials)" />
        </transition>
</view-state>
此段代码的功能是绑定cas登录过程中的用户名和密码,再次我们修改如下:
      <view-state id="viewLoginForm" view="casLoginView" model="credentials">
        <var name="credentials" class="org.jasig.cas.authentication.principal.UsernamePasswordCredentials" />
        <binder>
            <binding property="username" />
            <binding property="password" />
        </binder>
        <on-entry>
            <set name="viewScope.commandName" value="'credentials'" />
        </on-entry>
<transition on="submit" bind="true" validate="true" to="yzmSubmit">
            <set name="flowScope.credentials" value="credentials" />
            <evaluate expression="authenticationViaFormAction.doBind(flowRequestContext, flowScope.credentials)" />
        </transition>
</view-state>
也就是说,只需要修改realSubmit为yzmSubmit即可.然后加入如下配置:
      <!--fan add start-->
<action-state id="yzmSubmit">
        <evaluate expression="yzmViaFormAction.submit(flowRequestContext)" />
<transition on="success" to="realSubmit" />
<transition on="error" to="viewLoginForm" />
</action-state>
<!--fan add end-->
此段配置是自定义的验证码验证器,用来验证你提交的验证码的正确性.
  2.在web-info下找到cas-servlet.xml,打开后,加入
<!--fan add start-->
<bean id="yzmViaFormAction" class="com.ivan.zhang.servlet.YzmAction"
/>
<!--fan add end-->此配置是注册自定义的验证码
  3.编写如下类:
package com.ivan.zhang.servlet;

import com.ivan.zhang.CaptchaServiceSingleton;
import com.octo.captcha.service.image.ImageCaptchaService;
import java.io.PrintStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.jasig.cas.web.support.WebUtils;
import org.springframework.webflow.core.collection.ParameterMap;
import org.springframework.webflow.execution.RequestContext;

public class YzmAction
{
  public final String submit(RequestContext context)
    throws Exception
  {
    Boolean flag = Boolean.valueOf(false);
    System.out.println("YzmAction is submiting....................");
    String yzm = context.getRequestParameters().get("yzm");
    String captchaId = WebUtils.getHttpServletRequest(context).getSession().getId();
    flag = CaptchaServiceSingleton.getInstance().validateResponseForID(captchaId,
      yzm);
    if (flag.booleanValue()) {
      return "success";
    }
    return "error";
  }
}
其中,flag = CaptchaServiceSingleton.getInstance().validateResponseForID(captchaId,
      yzm);
此句话是为了验证提交的验证码和先前生成的验证码的正确性,以此作为验证结果跳转的依据.CaptchaServiceSingleton此类是自定义类,稍后会附加完整的类供下载调试.
4.打开web-info/view/jsp/default/ui/casLoginView.jsp,在密码下面加入<%--fan add start --%>
<img alt="yzm" src="captcha.jpg">
<spring:message code="screen.welcome.label.yzm.accesskey" var="yzmAccessKey" />
<form:input cssClass="required" cssErrorClass="error" id="yzm" size="25" tabindex="1" accesskey="${yzmAccessKey}" path="yzm" autocomplete="false" htmlEscape="true" />
<%--fan add end --%>
5. 最后一步则是注册验证码生成器,打开web.xml文件,加入
<servlet> 
        <servlet-name>jcaptcha</servlet-name> 
        <servlet-class>com.ivan.zhang.servlet.ImageCaptchaServlet</servlet-class> 
        <load-on-startup>0</load-on-startup> 
    </servlet>
<servlet-mapping> 
        <servlet-name>jcaptcha</servlet-name> 
        <url-pattern>/captcha.jpg</url-pattern> 
    </servlet-mapping>
ok,就这么简单.简单解释一下流程,web.xml中注册的类是用来调用自定义的验证码生成器,以便在显示登陆界面的时候绘制验证码图片,并在session中生成标志位并记录,当用户提交验证码和用户名密码时,会先走自定义的验证码验证器(此时会先验证验证码的正确性),如果正确,再走用户名和密码的验证,如果不正确,则直接跳转回登陆页面.yzm.jar是自定义的验证码生成器和验证类,直接打包好后放到web-info/lib下.
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