code: private AuthenticationProvider getAuthenticationProvider(String identifier) {
  
          // Iterate through all installed AuthenticationProviders, searching for
          // the given identifier
          for (AuthenticationProvider authProvider : authProviders) {
              if (authProvider.getIdentifier().equals(identifier))
                  return authProvider;
          }
  
          // No such AuthenticationProvider found
          return null;
  
      }
docs: Returns the AuthenticationProvider having the given identifier. If no
  such AuthenticationProvider has been loaded, null is returned.
  
  @param identifier
  The identifier of the AuthenticationProvider to locate.
  
  @return
  The AuthenticationProvider having the given identifier, or null if
  no such AuthenticationProvider is loaded.