When I tried to make custom implementations for Spring Data Repository, It was not working. My custom implementation code is like this. {code} public class BankRepositoryCustomImpl implements BankRepositoryCustom { ... } {code} Problem is that there is the naming convention for custom implementation class. See Referenece. So ClassName should be BankRepositoryImpl. Referenece - https://docs.spring.io/spring-data/jpa/docs/current/reference/html/#_configuration