JacksonMappers.java

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;
import com.google.common.collect.ImmutableList;
import org.checkerframework.checker.nullness.qual.MonotonicNonNull;

import java.io.IOException;
import java.util.UUID;

public class JacksonMappers {

    private static final ObjectMapper mapper = new ObjectMapper();


    public static void main(String[] args) throws JsonProcessingException {
        ImmutableList<UUID> ids = ImmutableList.of(UUID.randomUUID(), UUID.randomUUID());
        MyObject object = new MyObject("Some arbitrary value.", ids);
        MyJacksonDto dto = new MyJacksonDto(object);
        String json = mapper.writeValueAsString(dto);
        System.out.println(json);
    }


    public static final class MySerializer extends StdSerializer<MyJacksonDto> {

        MySerializer() {
            super(MyJacksonDto.class);
        }

        @Override
        public void serialize(MyJacksonDto value,
                              JsonGenerator gen,
                              SerializerProvider provider)
                throws IOException {
            String flatJson = mapper.writeValueAsString(value.object);
            gen.writeStartObject();
            gen.writeObjectField("object", value.object);
            gen.writeStringField("flatJson", flatJson);
            gen.writeEndObject();
        }
    }


    @JsonSerialize(using = MySerializer.class)
    public static final class MyJacksonDto {


        private final MyObject object;
        private @MonotonicNonNull String flatJson;

        public MyJacksonDto(MyObject object) {
            this.object = object;
        }

        public String getFlatJson() {
            return flatJson;
        }

        public MyObject getObject() {
            return object;
        }
    }

    public static final class MyObject {

        private final String value;
        private final ImmutableList<UUID> ids;

        public MyObject(String value, ImmutableList<UUID> ids) {
            this.value = value;
            this.ids = ids;
        }

        public ImmutableList<UUID> getIds() {
            return ids;
        }

        public String getValue() {
            return value;
        }
    }
}