config/src/main/java/org/springframework/security/config/http/DefaultFilterChainValidator.java
private void checkFilterStack(List<Filter> filters) {
		checkForDuplicates(SecurityContextPersistenceFilter.class, filters);
		checkForDuplicates(UsernamePasswordAuthenticationFilter.class, filters);
		checkForDuplicates(SessionManagementFilter.class, filters);
		checkForDuplicates(BasicAuthenticationFilter.class, filters);
		checkForDuplicates(SecurityContextHolderAwareRequestFilter.class, filters);
		checkForDuplicates(JaasApiIntegrationFilter.class, filters);
		checkForDuplicates(ExceptionTranslationFilter.class, filters);
		checkForDuplicates(FilterSecurityInterceptor.class, filters);
	}
private void checkFilterStack(List<Filter> filters) {
		checkForDuplicates(SecurityContextPersistenceFilter.class, filters);
		checkForDuplicates(UsernamePasswordAuthenticationFilter.class, filters);
		checkForDuplicates(SessionManagementFilter.class, filters);
		checkForDuplicates(BasicAuthenticationFilter.class, filters);
		checkForDuplicates(SecurityContextHolderAwareRequestFilter.class, filters);
		checkForDuplicates(JaasApiIntegrationFilter.class, filters);
		checkForDuplicates(ExceptionTranslationFilter.class, filters);
		checkForDuplicates(FilterSecurityInterceptor.class, filters);
	}
Checks the filter list for possible errors and logs them