config/src/main/java/org/springframework/security/config/annotation/web/configurers/CsrfConfigurer.java
@SuppressWarnings("unchecked")
	private InvalidSessionStrategy getInvalidSessionStrategy(H http) {
		SessionManagementConfigurer<H> sessionManagement = http
				.getConfigurer(SessionManagementConfigurer.class);
		if (sessionManagement == null) {
			return null;
		}
		return sessionManagement.getInvalidSessionStrategy();
	}
@SuppressWarnings("unchecked")
	private InvalidSessionStrategy getInvalidSessionStrategy(H http) {
		SessionManagementConfigurer<H> sessionManagement = http
				.getConfigurer(SessionManagementConfigurer.class);
		if (sessionManagement == null) {
			return null;
		}
		return sessionManagement.getInvalidSessionStrategy();
	}
Gets the default {@link InvalidSessionStrategy} from the
{@link SessionManagementConfigurer#getInvalidSessionStrategy()} or null if not
available.

@param http the {@link HttpSecurityBuilder}
@return the {@link InvalidSessionStrategy}