My application uses CAS 3.4.11, Spring 3.1 and Hibernate 4.
My login-webflow.xml uses spring-webflow-2.0.xsd and the login flow is given below,

```
<var name="credentials" class="org.jasig.cas.authentication.principal.UsernamePasswordCredentials" />

   <on-start>
     <evaluate expression="initialFlowSetupAction" />
   </on-start>

   <view-state id="viewLoginForm" view="casLoginView" model="credentials">
     <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">
        <evaluate expression="authenticationViaFormAction.doBind(flowRequestContext, flowScope.credentials)" />
     </transition>
   </view-state>

```

The beans "initialFlowSetupAction" and "authenticationViaFormAction" are defined in cas-servlet.xml as,

```
<bean id="initialFlowSetupAction" class="org.jasig.cas.web.flow.InitialFlowSetupAction"
        p:argumentExtractors-ref="argumentExtractors"
        p:warnCookieGenerator-ref="warnCookieGenerator"
        p:ticketGrantingTicketCookieGenerator-ref="ticketGrantingTicketCookieGenerator"/>

  <bean id="authenticationViaFormAction" class="org.jasig.cas.web.flow.AuthenticationViaFormAction"
        p:centralAuthenticationService-ref="centralAuthenticationService"
        p:warnCookieGenerator-ref="warnCookieGenerator"/>

```

The issue here is, the InitialFlowSetupAction is called while launch the login page. On click of "Sign In" button the bind/submit method of AuthenticationViaFormAction class should be invoked. But always the InitialFlowSetupAction is called and the form is redisplayed with out any exception. Atleast I could track if there is an exception. 

Can it be a binding issue with username and password fields of the form to set its properties to UsernamePasswordCredentials? 

Basically I would like to know why InitialFlowSetupAction is invoked onclick of "Sign In" button?