config/src/main/java/org/springframework/security/config/annotation/web/configurers/AbstractAuthenticationFilterConfigurer.java
public final T failureUrl(String authenticationFailureUrl) {
		T result = failureHandler(new SimpleUrlAuthenticationFailureHandler(
				authenticationFailureUrl));
		this.failureUrl = authenticationFailureUrl;
		return result;
	}
public final T failureUrl(String authenticationFailureUrl) {
		T result = failureHandler(new SimpleUrlAuthenticationFailureHandler(
				authenticationFailureUrl));
		this.failureUrl = authenticationFailureUrl;
		return result;
	}
The URL to send users if authentication fails. This is a shortcut for invoking
{@link #failureHandler(AuthenticationFailureHandler)}. The default is
"/login?error".

@param authenticationFailureUrl the URL to send users if authentication fails (i.e.
"/login?error").
@return the {@link FormLoginConfigurer} for additional customization