cas添加验证码

cas添加验证码，折腾了好久，终于整理好了，很大部分都是借鉴http://binghejinjun.iteye.com/blog/1255293这个的。但是他的有一个很不好的地方就是不能提升验证码错误！

红色字体的为我添加的，可以提示验证码错误！很简单，感谢。原作者。谢谢。

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，messageContext)" /> 
<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"; 
    } 
//我添加的改动。提示验证码错误

MessageBuilder msgBuilder = new MessageBuilder();
msgBuilder.defaultText("验证码错误！");
messageContext.addMessage(msgBuilder.error().build());

    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.