[FIXED] With all configurations DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES not working

Issue

I tried all the solutions provided on these below SO threads:

Jackson FAIL_ON_UNKNOWN_PROPERTIES to false not working

jackson Unrecognized field

Spring Boot Web- Set FAIL_ON_UNKNOWN_PROPERTIES to false in Jackson

And around 10 more similar SO threads.

Here is my Spring Boot application:

@SpringBootApplication(exclude = { DataSourceAutoConfiguration.class })
public class MyApplication {

    @Autowired
    private WebClient webClient;

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

    }

    @Bean
    public CommandLineRunner demo() {
        return (args) -> {
            getDetails("abcd12345");

        };
    }

    private void getDetails(String nodeId) throws IOException {
        Mono<String> mono = webClient.get().uri("/end/point").retrieve().bodyToMono(String.class);
        System.out.println(mono.block());
        final ObjectNode node = objectMapper().readValue(mono.block(), ObjectNode.class);
        System.out.println(node.get("parent").get("properties").get("nonExisting:keyhere").asText());  // NPE here
    }

    @Bean
    public ObjectMapper objectMapper() {
        return Jackson2ObjectMapperBuilder.json().featuresToEnable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES)
                .build();
    }

    @Bean
    public Jackson2ObjectMapperBuilder objectMapperBuilder() {
        Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
        builder.failOnUnknownProperties(false);
        return builder;
    }

}

And my application.properties file has:

spring.jackson.deserialization.FAIL_ON_UNKNOWN_PROPERTIES=false

Output:

Caused by: java.lang.NullPointerException: null
    at com.springbatch.parallel.processing.Application.getDetails(MyApplication .java:43)

But still I am getting NullPointerException (NPE) for non-existing key. I am trying to disable FAIL_ON_UNKNOWN_PROPERTIES. What I am missing here?

Solution

You will need to cope with the possibility of null being returned by any of the calls in that chained method call as follows:

private void getDetails(String nodeId) throws IOException {
    Mono<String> mono = webClient.get().uri("/end/point").retrieve().bodyToMono(String.class);
    System.out.println(mono.block());
    final ObjectNode node = objectMapper().readValue(mono.block(), ObjectNode.class);
    JsonNode parentNode = node.get("parent");
    if (parentNode != null) {
        JsonNode parentPropertiesNode = parentNode.get("properties");
        if (parentPropertiesNode != null) {
            JsonNode nonExistingKeyNode = parentPropertiesNode.get("nonExisting:keyhere");
            if (nonExistingKeyNode != null) {
                System.out.println(nonExistingKeyNode.asText());
            }
        }
    }
}

Additionally, avoid at all costs using block() in a Reactive stack. By doing this you are wasting all the benefits of using Spring WebFlux. Here is a very interesting online resource about common mistakes while using the Reactive stack: https://medium.com/javarevisited/five-mistakes-to-avoid-in-reactive-java-786927ffd2f6.

Answered By - João Dias