Properties.java

@Data
@Validated
@ConfigurationProperties("registration.kafka")
public class KafkaProperties {

    @NotEmpty(message = "Parameter 'bootstrap-servers' can not be empty")
    private String bootstrapServers;

    @NestedConfigurationProperty
    @NotNull(message = "Parameter 'some-activate' can not be null")
    private KafkaConsumerProperties someActivate;

}

@Data
public class KafkaConsumerProperties {

    @NotEmpty(message = "Parameter 'topic' can not be empty")
    private String topic;

    @NotEmpty(message = "Parameter 'group-id' can not be empty")
    private String groupId;
}