Question

I am building JSON from Java object tree using Jackson ObjectMapper. Some of my Java objects are collections and sometimes they might be empty. So if they are empty that ObjectMapper generates me: "attributes": [], and I want to exclude those kind of empty JSON arrays from my result. My current ObjectMapper config:

SerializationConfig config = objectMapper.getSerializationConfig();
config.setSerializationInclusion(JsonSerialize.Inclusion.NON_NULL);
config.set(SerializationConfig.Feature.WRAP_ROOT_VALUE, true);

From this post I’ve read that I can use:

config.setSerializationInclusion(JsonSerialize.Inclusion.NON_DEFAULT);

But that is generating me an error:

Caused by: java.lang.IllegalArgumentException: Class com.mycomp.assessments.evaluation.EvaluationImpl$1 has no default constructor; can not instantiate default bean value to support 'properties=JsonSerialize.Inclusion.NON_DEFAULT' annotation.

So how should I prevent those empty arrays to appear in my result?

Answer 1

You should use:

config.setSerializationInclusion(JsonSerialize.Inclusion.NON_EMPTY);

for Jackson 1 or

config.setSerializationInclusion(JsonInclude.Include.NON_EMPTY);

for Jackson 2