enablePassingNulls(true) not working when migrated to springboot 3.2.3

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04-10-2024

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Spring Boot 3.2.3: enablePassingNulls(true) – Why It's Not Working as Expected

Migrating your Spring Boot application to version 3.2.3 and encountering issues with the enablePassingNulls(true) setting? You're not alone! This common issue arises from significant changes in Spring Boot's data binding behavior, particularly with the introduction of the new org.springframework.web.bind.annotation.RequestBody annotation.

The Scenario: Null Values and Spring Boot 3.2.3

Let's imagine a scenario where your API accepts JSON payloads for updating data. In previous versions of Spring Boot, using enablePassingNulls(true) in your WebMvcConfigurer effectively allowed you to pass null values in the JSON body, which would update the corresponding fields in your domain objects to null.

@Configuration
public class WebConfig implements WebMvcConfigurer {

    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        ObjectMapper mapper = new ObjectMapper();
        mapper.enable(SerializationFeature.INDENT_OUTPUT);
        mapper.enable(DeserializationFeature.ACCEPT_EMPTY_STRING_AS_NULL_OBJECT);
        converter.setObjectMapper(mapper);
        converters.add(converter);
    }

    @Override
    public void addFormatters(FormatterRegistry registry) {
        registry.addConverter(new StringToLocalDateTimeConverter());
    }

    @Override
    public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
        configurer.defaultContentType(MediaType.APPLICATION_JSON);
        configurer.favorParameter(false);
        configurer.favorPathExtension(false);
        configurer.ignoreAcceptHeader(false);
        configurer.useJaf(false);
        configurer.mediaType("json", MediaType.APPLICATION_JSON);
    }
}

However, in Spring Boot 3.2.3, this behavior has changed. The RequestBody annotation now defaults to required = true, which means any fields not present in the JSON body will not be considered for updates, even if enablePassingNulls(true) is set. This can lead to unexpected behavior where fields are not updated to null as intended.

Understanding the Changes

Spring Boot 3.2.3 introduced a more strict approach to data binding. The RequestBody annotation's default required = true ensures that all fields mentioned in the request body are mandatory, regardless of whether they are present in the JSON payload.

This shift aims to promote data consistency and avoid unexpected side effects. It is now considered best practice to explicitly declare which fields in the JSON payload are required.

Addressing the Issue: Solutions and Workarounds

Here's how you can address the issue and ensure null values are handled as expected in Spring Boot 3.2.3:

1. Explicitly Set required = false: Modify your controller method to explicitly set the required attribute of the RequestBody annotation to false for the fields you wish to allow null values for:

   @PutMapping("/users/{id}")
   public ResponseEntity<User> updateUser(@PathVariable Long id,
                                       @RequestBody(required = false) User user) {
       // ...
   }
   

2. Use @RequestParam: For individual fields, consider using the @RequestParam annotation instead of @RequestBody. You can control the required attribute for each field using the @RequestParam annotation.

   @PutMapping("/users/{id}")
   public ResponseEntity<User> updateUser(@PathVariable Long id,
                                       @RequestParam(name = "name", required = false) String name,
                                       @RequestParam(name = "email", required = false) String email) {
       // ...
   }
   

3. Custom Deserialization: If you require more granular control over null handling, you can implement a custom deserializer for your domain objects. This allows you to specify how specific fields should handle null values during deserialization.

4. Update your application: Ensure that you are using the latest version of Spring Boot, as earlier versions might not include this behavior.

Conclusion: Embracing the Change

The shift in data binding behavior in Spring Boot 3.2.3 reflects a move towards more explicit data handling. While it might require adjustments to your existing code, it ultimately leads to better data integrity and predictability. By understanding these changes and adopting the recommended approaches, you can ensure that your applications seamlessly handle null values and maintain data consistency.