I have the following classes:

@Getter
@Setter
@Configuration
@Validated
@ConfigurationProperties(prefix = "event-processor.topic")
public class TopicProperties {

    @NestedConfigurationProperty
    private InputTopicProperties input;

    @NestedConfigurationProperty
    private OutputTopicProperties output;
}

@Getter
@Setter
@Validated
@Configuration
public class InputTopicProperties {
    /**
     * Input topic to read from. Must exist.
     */
    @NotEmpty
    private String name;
}

@Getter
@Setter
@Validated
@Configuration
public class OutputTopicProperties {

    @NotEmpty
    private String name;

    @Min(1)
    @Max(18)
    private int numPartitions = 12;

    // ... other fields

}

@Getter
@Setter
@Validated
@Configuration
@ConfigurationProperties(prefix = "event-processor.broker")
@EnableConfigurationProperties
public class BrokerProperties {

    @NotEmpty
    private String applicationId = "event-processor-streams-app";

    @NotEmpty
    private String bootstrapServers = "kafka:9092";

    // ... other fields

}

Together with the following application config:

event-processor:
  broker:
    application-id: test
    bootstrap-servers: localhost:29092
  topic:
    input:
      name: mytopic
    output:
      name: myoutput

Using Spring Boot 2.6.9 (I know, a bit old) I was able to keep all default that I had written (e.g. brokerProperties.applicationId, outputTopicProperties.partitions) and selectively override.

After switching to Spring Boot 3.2.5, I have the following behaviour:

1. I cannot override the default that I have provided in the source code
2. Nested configuration properties are not injected (e.g. topicProperties.getInput() == null)

Here is my main class:

@Log4j2
@SpringBootApplication
@RequiredArgsConstructor
//@ConfigurationPropertiesScan // tried this as well, did not help
public class ExtractorApplication {

    private final BrokerProperties brokerProperties;
    private final TopicProperties topicProperties;

    public static void main(String[] args) {
        SpringApplication.run(ExtractorApplication.class, args);
    }

    @PostConstruct
    public void logBrokerAndTopicInfo() {
        // gives only defaults
        logFromClass("application Id - {}", brokerProperties.getApplicationId());
        // gives only defaults
        logFromClass("connected to broker {}", brokerProperties.getBootstrapServers()); 
        // NPE
        logFromClass("reading from {}", topicProperties.getInput().getName());
        // NPE
        logFromClass("writing to {}", topicProperties.getOutput().getName());
    }

    private void logFromClass(String pattern, String msg) {
        log.info("{}: " + pattern, ExtractorApplication.class.getSimpleName(), msg);
    }

}

What am I doing wrong?