config/src/main/java/org/springframework/security/config/annotation/web/configurers/AbstractInterceptUrlConfigurer.java
private AccessDecisionManager getAccessDecisionManager(H http) {
		if (accessDecisionManager == null) {
			accessDecisionManager = createDefaultAccessDecisionManager(http);
		}
		return accessDecisionManager;
	}
private AccessDecisionManager getAccessDecisionManager(H http) {
		if (accessDecisionManager == null) {
			accessDecisionManager = createDefaultAccessDecisionManager(http);
		}
		return accessDecisionManager;
	}
If currently null, creates a default {@link AccessDecisionManager} using
{@link #createDefaultAccessDecisionManager(HttpSecurityBuilder)}. Otherwise returns the
{@link AccessDecisionManager}.

@param http the builder to use

@return the {@link AccessDecisionManager} to use