CAS delegate authentication - authentication

Question

I'm using CAS server 4.x and I'm trying to delegate authentication using google. My idea is that a web application A redirects to CAS for login, there the user presses a "login using google" and then he gets redirected to log in using google.
To achieve that I created a client application (A).
I run A and it redirects me to the CAS login page, there I press the "login using google" link and it redirects me to login with google, there I login and consent.
On the CAS side the info from google is received ok and the TGT is created. However, the server fails to redirect to A cause it doesn't have the redirect info in the session:
ERROR [org.jasig.cas.support.oauth.web.OAuth20CallbackAuthorizeController] - oauth20_callbackUrl is missing from the session and can not be retrieved.
Any idea of what could be wrong?
This is how I configured everything:
First, I followed the steps mentioned here:
http://jasig.github.io/cas/development/integration/Delegate-Authentication.html
In the login view I added:
login using google
applicationContext:
<bean id="google" class="org.pac4j.oauth.client.Google2Client">
<property name="key" value="key" />
<property name="secret" value="secret" />
</bean>
<bean id="clients" class="org.pac4j.core.client.Clients">
<property name="callbackUrl" value="http://localhost:8080/cas/login" />
<property name="clients">
<list>
<ref bean="google" />
</list>
</property>
</bean>
cas servlet:
<bean id="clientAction" class="org.jasig.cas.support.pac4j.web.flow.ClientAction">
<constructor-arg index="0" ref="centralAuthenticationService"/>
<constructor-arg index="1" ref="clients"/>
</bean>
deployerConfigContext:
<property name="authenticationMetaDataPopulators">
<util:list>
<bean class="org.jasig.cas.support.pac4j.authentication.ClientAuthenticationMetaDataPopulator" />
</util:list>
</property>
<bean id="primaryAuthenticationHandler"
class="org.jasig.cas.support.pac4j.authentication.handler.support.ClientAuthenticationHandler">
<constructor-arg index="0" ref="clients"/>
</bean>
Then I added an OAuth client in the deployerConfigContext:
registeredServicesList:
<bean class="org.jasig.cas.support.oauth.services.OAuthRegisteredService">
<property name="id" value="1" />
<property name="name" value="serviceName" />
<property name="description" value="Service Description" />
<property name="serviceId" value="http://localhost:8080/A/" />
<property name="clientId" value="123" />
<property name="clientSecret" value="123" />
</bean>

Answer 1

The error you get happens only if you enable OAuth server support, but what you want is to enable OAuth client support (based on pac4j) to be able to delegate the authentication to Google. You have the right link to the documentation, but you should check you followed every steps (there is no "OAuthRegisteredService").