Enable/Disable Null Fields in a JSON Response

Problem

We need to have a SWITCH to enable or disable the inclusion of NULL fields in the API Response in the form of property:

Solution

• In this example, ‘RegistationResponse’ is the response object for our API. This is the object in which we want to use the ‘Enable/Disable Null fields’ flag so that the response contains NULL fields or not based on the property ‘config.response.format.include.null’ present in the application.properties file:

• Declare the property ‘config.response.format.include.null’ in application.properties file:

• Bind this property to a class-level property so that the value can be read:

• Implement the actual logic to include nulls based on the property value by:
  • Creating an instance of com.fasterxml.jackson.databind.ObjectMapper.
  • Setting SerializationInclusion property of the created mapper to Include.NON_NULL if the global property value is false, otherwise set to Include.ALWAYS.
  • Serializing the Response object to a String using the mapper & return the String. Make sure to handle JsonProcessingException.

See below for the actual code snippet to be added while constructing the JSON Response as part of the API implementation:

Where regRespStr is the JSON String with NULL exclusion/inclusion applied.

Source code is available in GitHub @ this location.

Common Mistakes

Initially, I tried with the Spring Boot’s readily available approaches, which were not successful, such as:

• Having spring.jackson.default-property-inclusion property in application.properties. This property takes values such as: always/non_null/non_absent/non_default/non_empty.
• Extending WebMvcConfigurationSupport class and customize the Spring Boot configuration, see below:

• Creating an instance of org.springframework.http.converter.json.Jackson2ObjectMapperBuilderCustomizer, see below:

Conclusion

The decision of whether to include the NULL fields in a JSON can be externalized using Spring Boot.

Source code is available in GitHub @ this location.