Good afternoon João
It is possible to have more than one Authentication Provider, in fact, as many as you want in the same application.
According to the documentation, it is possible to use existing providers in Spring Security and also create their customized ones. After creation, you need to register in an Authentication-manager.
Ex:
<authentication-manager>
<authentication-provider ref="restAuthProvider/>
<authentication-provider ref="basicAuthProvider"/>
</authentication-manager>
<bean id="restAuthProvider" class="br.com.auths.RestAuthProvider">
</bean>
<bean id="basicAuthProvider" class="br.com.auths.BasicAuthProvider">
</bean>
Ref: http://docs.spring.io/spring-security/site/docs/4.0.3.RELEASE/reference/htmlsingle/#ns-auth-manager