CAS研究（四）-登出/logout

很多童鞋对单点登出不是很理解，下面我们来看看单点登出到底做了什么东西，

我们来看看怎么从配置到代码的。

1）web.xml

com.bingo.tfp.web.init.SafeDispatcherServlet

<servlet-mapping>
<servlet-name>cas</servlet-name>
<url-pattern>/logout</url-pattern>
</servlet-mapping>

从上面可以知道，所有/logout的请求都交给SafeDispatcherServlet去分发了，查看代码可以知道这个Servlet只是对 org.springframework.web.servlet.DispatcherServlet一次包装，将所有请求都交给 org.springframework.web.servlet.DispatcherServlet去处理了。

2）cas-servlet.xml

handlerMappingC的bean里面有一段配置：

<prop key="/logout">
logoutController
</prop>

也就是说，所有/logout的请求，都交给一个beanid为logoutController的Bean去处理了，那么我们看看com.bingo.tfp.web.LogoutController到底做了什么事情，

<bean id="logoutController" class="com.bingo.tfp.web.LogoutController"
p:centralAuthenticationService-ref="centralAuthenticationService"
p:logoutView="casLogoutView"
p:warnCookieGenerator-ref="warnCookieGenerator"
p:ticketGrantingTicketCookieGenerator-ref="ticketGrantingTicketCookieGenerator"
p:followServiceRedirects="true"/>
我们看看源码是怎么操作的：

protected ModelAndView handleRequestInternal(
     final HttpServletRequest request, final HttpServletResponse response)
     throws Exception {
    //取得TGT_ID
     final String ticketGrantingTicketId = this.ticketGrantingTicketCookieGenerator.retrieveCookieValue(request);
     // 取得service参数数据，这个参数是可选参数
     final String service = request.getParameter("service");

     //如果TGT不为空
     if (ticketGrantingTicketId !=  null) {
        //那么在centralAuthenticationService中销毁
         this.centralAuthenticationService
             .destroyTicketGrantingTicket(ticketGrantingTicketId);
         //ticketGrantingTicketCookieGenerator 中销毁cookie
         this.ticketGrantingTicketCookieGenerator.removeCookie(response);
         //warnCookieGenerator 中销毁
         this.warnCookieGenerator.removeCookie(response);
     }
     // 如果参数：followServiceRedirects为true 同时service不会空的时候，跳转到service指定的URL
     if (this.followServiceRedirects && service != null) {
         return new ModelAndView(new RedirectView(service));
     }
     //否则，跳转到logoutView指定的页面
     return new ModelAndView(this.logoutView);
}

   protected ModelAndView handleRequestInternal(
        final HttpServletRequest request, final HttpServletResponse response)
        throws Exception {
    	//取得TGT_ID
        final String ticketGrantingTicketId = this.ticketGrantingTicketCookieGenerator.retrieveCookieValue(request);
        // 取得service参数数据，这个参数是可选参数
        final String service = request.getParameter("service");
        
        //如果TGT不为空
        if (ticketGrantingTicketId != null) {
        	//那么在centralAuthenticationService中销毁
            this.centralAuthenticationService
                .destroyTicketGrantingTicket(ticketGrantingTicketId);
            //ticketGrantingTicketCookieGenerator 中销毁cookie
            this.ticketGrantingTicketCookieGenerator.removeCookie(response);
            //warnCookieGenerator 中销毁
            this.warnCookieGenerator.removeCookie(response);
        }
        // 如果参数：followServiceRedirects为true 同时service不会空的时候，跳转到service指定的URL
        if (this.followServiceRedirects && service != null) {
            return new ModelAndView(new RedirectView(service));
        }
        //否则，跳转到logoutView指定的页面
        return new ModelAndView(this.logoutView);
    }

是不是很简单，那么有童鞋要问了，那么时候访问客户端呢？不要着急，我们在来看看

this.centralAuthenticationService
               .destroyTicketGrantingTicket(ticketGrantingTicketId);

 this.centralAuthenticationService
                .destroyTicketGrantingTicket(ticketGrantingTicketId);

做了什么事情：

public void destroyTicketGrantingTicket(final String ticketGrantingTicketId) {
        //断言参数不能空
        Assert.notNull(ticketGrantingTicketId);

        if (log.isDebugEnabled()) {
            log.debug("Removing ticket [" + ticketGrantingTicketId + "] from registry.");
        }
        // 从票据仓库中取得TGT票据
        final TicketGrantingTicket ticket = (TicketGrantingTicket) this.ticketRegistry.getTicket(ticketGrantingTicketId, TicketGrantingTicket.class);
        //如果票据为空，则直接返回
        if (ticket ==  null) {
            return;
        }

        if (log.isDebugEnabled()) {
            log.debug("Ticket found.  Expiring and then deleting.");
        }
        //叫票据注销，也就是设置为期满（或者叫做过期）
        ticket.expire();
        //在票据仓库中删除该票据
        this.ticketRegistry.deleteTicket(ticketGrantingTicketId);
    }

public void destroyTicketGrantingTicket(final String ticketGrantingTicketId) {
        //断言参数不能空
    	Assert.notNull(ticketGrantingTicketId);
    	
        if (log.isDebugEnabled()) {
            log.debug("Removing ticket [" + ticketGrantingTicketId + "] from registry.");
        }
        // 从票据仓库中取得TGT票据
        final TicketGrantingTicket ticket = (TicketGrantingTicket) this.ticketRegistry.getTicket(ticketGrantingTicketId, TicketGrantingTicket.class);
        //如果票据为空，则直接返回
        if (ticket == null) {
            return;
        }

        if (log.isDebugEnabled()) {
            log.debug("Ticket found.  Expiring and then deleting.");
        }
        //叫票据注销，也就是设置为期满（或者叫做过期）
        ticket.expire();
        //在票据仓库中删除该票据
        this.ticketRegistry.deleteTicket(ticketGrantingTicketId);
    }

很奇怪是不是，居然还没有请求客户端的东西，别急嘛。我们再来看看

ticket.expire();

ticket.expire();

做了什么，这个是TicketGrantingTicketImpl来实现的。

public synchronized void expire() {
        this.expired = true;
        logOutOfServices();
    }
是不是发现新大陆了？

下面是logOutOfServices()方法的源代码：

private void logOutOfServices() {
       for (final Entry<String, Service> entry : this.services.entrySet()) {

           if (!entry.getValue().logOutOfService(entry.getKey())) {
               LOG.warn("Logout message not sent to [" + entry.getValue().getId() + "]; Continuing processing...");
           }
       }
   }

 private void logOutOfServices() {
        for (final Entry<String, Service> entry : this.services.entrySet()) {

            if (!entry.getValue().logOutOfService(entry.getKey())) {
                LOG.warn("Logout message not sent to [" + entry.getValue().getId() + "]; Continuing processing...");   
            }
        }
    }

哇，原来在TGT票据里面有个Entry来保存用户访问过的service对象，key是对应service的seesionID,那么是不是使用https请求客户无端呢？看看AbstractWebApplicationService类就知道咯，

public synchronized boolean logOutOfService(final String sessionIdentifier) {
       if (this.loggedOutAlready) {
           return  true;
       }

       LOG.debug("Sending logout request for: " + getId());

       final String logoutRequest =  "<samlp:LogoutRequest xmlns:samlp=\"urn:oasis:names:tc:SAML:2.0:protocol\" ID=\""
           + GENERATOR.getNewTicketId("LR")
           + "\" Version=\"2.0\" IssueInstant=\"" + SamlUtils.getCurrentDateAndTime()
           + "\"><saml:NameID xmlns:saml=\"urn:oasis:names:tc:SAML:2.0:assertion\">@NOT_USED@</saml:NameID><samlp:SessionIndex>"
           + sessionIdentifier + "</samlp:SessionIndex></samlp:LogoutRequest>";

       this.loggedOutAlready =  true;

       if (this.httpClient != null) {
           return  this.httpClient.sendMessageToEndPoint(getOriginalUrl(), logoutRequest, true);
       }

       return false;
   }

 public synchronized boolean logOutOfService(final String sessionIdentifier) {
        if (this.loggedOutAlready) {
            return true;
        }

        LOG.debug("Sending logout request for: " + getId());

        final String logoutRequest = "<samlp:LogoutRequest xmlns:samlp=\"urn:oasis:names:tc:SAML:2.0:protocol\" ID=\""
            + GENERATOR.getNewTicketId("LR")
            + "\" Version=\"2.0\" IssueInstant=\"" + SamlUtils.getCurrentDateAndTime()
            + "\"><saml:NameID xmlns:saml=\"urn:oasis:names:tc:SAML:2.0:assertion\">@NOT_USED@</saml:NameID><samlp:SessionIndex>"
            + sessionIdentifier + "</samlp:SessionIndex></samlp:LogoutRequest>";
        
        this.loggedOutAlready = true;
        
        if (this.httpClient != null) {
            return this.httpClient.sendMessageToEndPoint(getOriginalUrl(), logoutRequest, true);
        }
        
        return false;
    }

怎么样，这样是不是对单点登出细节比较清楚呢。