config/src/main/java/org/springframework/security/config/annotation/authentication/builders/AuthenticationManagerBuilder.java
public AuthenticationManagerBuilder parentAuthenticationManager(
			AuthenticationManager authenticationManager) {
		if (authenticationManager instanceof ProviderManager) {
			eraseCredentials(((ProviderManager) authenticationManager)
					.isEraseCredentialsAfterAuthentication());
		}
		this.parentAuthenticationManager = authenticationManager;
		return this;
	}
public AuthenticationManagerBuilder parentAuthenticationManager(
			AuthenticationManager authenticationManager) {
		if (authenticationManager instanceof ProviderManager) {
			eraseCredentials(((ProviderManager) authenticationManager)
					.isEraseCredentialsAfterAuthentication());
		}
		this.parentAuthenticationManager = authenticationManager;
		return this;
	}
public AuthenticationManagerBuilder parentAuthenticationManager ( AuthenticationManager authenticationManager ) { if ( authenticationManager instanceof ProviderManager ) { eraseCredentials ( ( ( ProviderManager ) authenticationManager ) . isEraseCredentialsAfterAuthentication ( ) ) ; } this . parentAuthenticationManager = authenticationManager ; return this ; }
Allows providing a parent {@link AuthenticationManager} that will be tried if this
{@link AuthenticationManager} was unable to attempt to authenticate the provided
{@link Authentication}.

@param authenticationManager the {@link AuthenticationManager} that should be used
if the current {@link AuthenticationManager} was unable to attempt to authenticate
the provided {@link Authentication}.
@return the {@link AuthenticationManagerBuilder} for further adding types of
authentication
Allows providing a parent { @link AuthenticationManager } that will be tried if this { @link AuthenticationManager } was unable to attempt to authenticate the provided { @link Authentication } .