Is it possible to specify the order of ObjectNode properties without using annotations?

Jackson allows users to specify an explicit serialization order for ObjectNode properties using the @JsonProperty(index = ?) annotation. Meaning, given properties a, b, c I can instruct Jackson to serialize them in the following order: b, a, c. I control the exact serialization order.

Is it possible to achieve the same without the use of annotations?

I do not want alphabetic sorting. I want to specify an explicit sorting order.

You can extend com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector class and provide your order for any class you want by overriding findSerializationPropertyOrder method.

import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.introspect.AnnotatedClass;
import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
import com.fasterxml.jackson.databind.json.JsonMapper;
import lombok.Data;

public class JacksonAnnotationIntrospectorApp {
	private final static JsonMapper JSON_MAPPER = JsonMapper.builder()
			.enable(SerializationFeature.INDENT_OUTPUT)
			.annotationIntrospector(new DynamicOrderJacksonAnnotationIntrospector())
			.build();

	public static void main(String[] args) throws Exception {
		var pojo = new DynamicOrderPojo();
		pojo.setA("A");
		pojo.setB(1);
		pojo.setC(3.33);

		JSON_MAPPER.writeValue(System.out, pojo);
	}
}

class DynamicOrderJacksonAnnotationIntrospector extends JacksonAnnotationIntrospector {

	@Override
	public String[] findSerializationPropertyOrder(AnnotatedClass ac) {
		if (ac.getRawType() == DynamicOrderPojo.class) {
			return new String[]{"b", "a", "c"};
		}
		return super.findSerializationPropertyOrder(ac);
	}
}

@Data
class DynamicOrderPojo {

	private String a;
	private Integer b;
	private Double c;
}

Above code prints:

{
  "b" : 1,
  "a" : "A",
  "c" : 3.33
}

See also:

• Custom serializer/deserializer for a collection, specifically a set