Mapping a JSON Array to POJO using Lombok

Question

I've looked at similar questions but it doesn't seem to address my issue. I have a JSON payload that's returned from a Feign webservice call that I'm mapping to a POJO.

JSON

{
   "fields":[
      {
        "field_one":"one value",
         "field_two":"two value",
      },
      {
         "field_one":"one value",
         "field_two":"two value",
      }
   ]
}

POJO - Wrapper Class

@Data
@NoArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class FieldsResponse {

    public List<FieldInfo> fields;

}

POJO - Detail Class

@Data
@NoArgsConstructor
@JsonInclude(JsonInclude.Include.NON_NULL)
public class FieldInfo{

    @JsonProperty("field_one")
    private String fieldOne;

    @JsonProperty("field_two")
    private String fieldTwo;
}

The POJO's are not being populated. If I change items in the wrapper POJO to a JsonArray everything works fine (i.e.: I can see the JSON response correctly). I've tried initializing the list in the wrapper object and have also experimented with using a vector instead.

Any ideas?

ETA: If I remove the @JsonPropery("field_one") mapping and rename the variable from fieldOne to field_one then it works. But this is not how I want it to work.

Answer 1

The code below worked fine.

Versions:

• AdoptOpenJDK 14
• Eclipse: 2020-03 (4.15.0)
• junit: 5.6.2
• log4j2: 2.13.3
• jackson: 2.11.0
• lombok: 1.18.12

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;

import java.util.List;

import org.junit.jupiter.api.Test;

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;

import lombok.Data;
import lombok.extern.log4j.Log4j2;

@Log4j2
public class Q62195156 {

    // @formatter:off
    static final String JSON="{\"fields\":[{\"field_one\":\"one value\",\"field_two\":\"two value\"},{\"field_one\":\"one value\",\"field_two\":\"two value\"}]}";
    // @formatter:on


    static final ObjectMapper OBJECT_MAPPER = new ObjectMapper();

    @Test
    void test() throws JsonMappingException, JsonProcessingException {

        var fieldsResponse = OBJECT_MAPPER.readValue(JSON, FieldsResponse.class);
        LOGGER.info("fieldResponse: {}", fieldsResponse);

        var fields = fieldsResponse.getFields();
        LOGGER.info("fields: {}", fieldsResponse);

        assertNotNull(fields, "fields");
        var fieldInfo0 = fields.get(0);
        LOGGER.info("fieldInfo0: {}", fieldInfo0);
        assertNotNull(fieldInfo0, "fieldInfo0");

        assertEquals(fieldInfo0.getFieldOne(), "one value", "fieldInfo0.getFieldOne()");
        assertEquals(fieldInfo0.getFieldTwo(), "two value", "fieldInfo0.getFieldTwo()");
        var fieldInfo1 = fields.get(1);
        LOGGER.info("fieldInfo1: {}", fieldInfo1);
        assertNotNull(fieldInfo1, "fieldInfo1");
        assertEquals(fieldInfo1.getFieldOne(), "one value", "fieldInfo1.getFieldOne()");
        assertEquals(fieldInfo1.getFieldTwo(), "two value", "fieldInfo1.getFieldTwo()");

    }

    @Data
    @JsonInclude(JsonInclude.Include.NON_NULL)
    static class FieldsResponse {

        public List<FieldInfo> fields;

    }

    @Data
    @JsonInclude(JsonInclude.Include.NON_NULL)
    static class FieldInfo {

        @JsonProperty("field_one")
        private String fieldOne;

        @JsonProperty("field_two")
        private String fieldTwo;
    }
}

Results:

13:14:42.344 [main] INFO  io.jeffmaxwell.stackoverflow.Q62195156 - fieldResponse: Q62195156.FieldsResponse(fields=[Q62195156.FieldInfo(fieldOne=one value, fieldTwo=two value), Q62195156.FieldInfo(fieldOne=one value, fieldTwo=two value)])
13:14:42.347 [main] INFO  io.jeffmaxwell.stackoverflow.Q62195156 - fields: Q62195156.FieldsResponse(fields=[Q62195156.FieldInfo(fieldOne=one value, fieldTwo=two value), Q62195156.FieldInfo(fieldOne=one value, fieldTwo=two value)])
13:14:42.349 [main] INFO  io.jeffmaxwell.stackoverflow.Q62195156 - fieldInfo0: Q62195156.FieldInfo(fieldOne=one value, fieldTwo=two value)
13:14:42.351 [main] INFO  io.jeffmaxwell.stackoverflow.Q62195156 - fieldInfo1: Q62195156.FieldInfo(fieldOne=one value, fieldTwo=two value)