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How to add field names and values of a json object into List<String> using jsonNode

Tarang
March 1, 2023
276 views
3 votes
3 Answers

I have an expected json file as below. It is a nested object

{
    "contact_info": [{
        "contact_id": "Contact_001",
        "contact_status": {
            "exam_status": 0,
            "term_list": [{
                "term_code": 110,
                "t_list": [{
                        "s_code": "12001",
                        "sexam_status": 0
                    },
                    {
                        "s_code": "13001",
                        "sexam_status": 1
                    }
                ]
            }]
        }
    }]
}

How to add all field name and value of all items inside this object into List?
I tried using the following way but it is not as expected.

//Get all key name in json object

```public static List<String> getAllKeysInJsonUsingJsonNodeFieldNames(String json) {
    ObjectMapper mapper = new ObjectMapper()
    List<String> keys = new ArrayList<>();
    JsonNode jsonNode = mapper.readTree(json);
    getAllKeysUsingJsonNodeFields(jsonNode, keys);
    return keys;
}

public static void getAllKeysUsingJsonNodeFields(JsonNode jsonNode, List<String> keys) {
    if (jsonNode.isObject()) {
        Iterator<Map.Entry<String, JsonNode>> fields = jsonNode.fields();
        fields.forEachRemaining({def field ->
            keys.add(field.getKey());
            getAllKeysUsingJsonNodeFields((JsonNode) field.getValue(), keys);
        });
    } else if (jsonNode.isArray()) {
        ArrayNode arrayField = (ArrayNode) jsonNode;
        arrayField.forEach({def node ->
            getAllKeysUsingJsonNodeFields(node, keys);
        });
    }
}```

The result as below => It only shows only field name without figure out that field belong to which object

TagName[i] = s_code

I expect that the result should be below, specifically, I want to field name should be shown it belongs to which object => Could you tell me how to resolve it?

TagName[i] = contact_status.term_list[0].t_list[0].s_code

Sorry for I’m a new in Java => If anyone know a way to resolve it please tell me in more details. Thank you so much!

Answers

Below code for add field names and values of a JSON object into List<String> using jsonNode:

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

public class JsonToListExample {
    public static void main(String[] args) throws Exception {
        String jsonStr = "{"contact_info":[{"contact_id":"Contact_001","contact_status":{"exam_status":0,"term_list":[{"term_code":110,"t_list":[{"s_code":12001,"sexam_status":0},{"s_code":13001,"sexam_status":1}]}]}}]}";
        ObjectMapper mapper = new ObjectMapper();
        JsonNode rootNode = mapper.readTree(jsonStr);
        List<String> fieldList = new ArrayList<>();
        checkFields(rootNode, fieldList);
        System.out.println(fieldList);

    }

    private static void checkFields(JsonNode node, List<String> fieldList) {
        Iterator<String> fieldNames = node.fieldNames();
        while (fieldNames.hasNext()) {
            String fieldName = fieldNames.next();
            JsonNode fieldValue = node.get(fieldName);
            if (fieldValue.isObject()) {
                checkFields(fieldValue, fieldList);
            } else if (fieldValue.isArray()) {
                for (JsonNode arrayNode : fieldValue) {
                    checkFields(arrayNode, fieldList);
                }
            } else {
                String fieldStr = fieldName + ": " + fieldValue.toString();
                fieldList.add(fieldStr);
            }
        }
    }
}

This code does what you want.

private static String jsonParserTest() {
    try {
        Map createdMap = new HashMap<String, Object>();
        Map<String, Object> tempMap  = new HashMap<>();
        List<Map> tempList = new ArrayList<>();
        tempMap.put("s_code", 12001);
        tempMap.put("sexam_status", 0);
        tempList.add(tempMap);
        tempMap = new HashMap<>();
        tempMap.put("s_code", 13001);
        tempMap.put("sexam_status", 1);
        tempList.add(tempMap);
        tempMap  = new HashMap<>();
        tempMap.put("term_code", 110);
        tempMap.put("t_list", tempList);
        tempList = new ArrayList<>();
        tempList.add(tempMap);
        tempList = new ArrayList<>();
        tempList.add(tempMap);
        tempMap  = new HashMap<>();
        tempMap.put("exam_status", 0);
        tempMap.put("term_list", tempList);
        Map<String, Object> tempMap2  = new HashMap<>();
        tempMap2.put("contact_status", tempMap);
        tempMap2.put("contact_id", "Contact_001");
        tempList = new ArrayList<>();
        tempList.add(tempMap2);
        createdMap.put("contact_info", tempList);
        String jsonString = JsonUtils.writeObjectToJsonString(createdMap);
        System.out.println(jsonString);
        return jsonString;
    } catch (IOException e) {
        System.out.println(TextUtils.getStacktrace(e));
    }
}

The return String is:

{
   "contact_info": {
      "contact_status": {
         "exam_status": 0,
         "term_list": [
            {
               "t_list": [
                  {
                     "s_code": 12001,
                     "sexam_status": 0
                  },
                  {
                     "s_code": 13001,
                     "sexam_status": 1
                  }
               ],
               "term_code": 110
            }
         ]
      },
      "contact_id": "Contact_001"
   }
}

And this String is the same Json as yours. Basically you need to build your map the way you want your JSON to look and than just serialize it to Json. In This code I used classes JsonUtils and TextUtils. JsonUtils class is a thin wrapper over Jason-Jackson library and it makes serializing and parsing simpler. Thise classes come from Open Source MgntUtils library written and maintained by me. You can get this library as Maven artifact here or here and also on Github with source code and Javadoc. Here is JsoonUtils Javadoc

You can use JSON library such as Josson to do the transformation.

https://github.com/octomix/josson

Deserialization

Josson josson = Josson.fromJsonString(
    "{" +
    "    "contact_info": [{" +
    "        "contact_id": "Contact_001"," +
    "        "contact_status": {" +
    "            "exam_status": 0," +
    "            "term_list": [{" +
    "                "term_code": 110," +
    "                "t_list": [{" +
    "                        "s_code": 12001," +
    "                        "sexam_status": 0" +
    "                    }," +
    "                    {" +
    "                        "s_code": 13001," +
    "                        "sexam_status": 1" +
    "                    }" +
    "                ]" +
    "            }]" +
    "        }" +
    "    }]" +
    "}");

Query the keys and values in separate arrays

Josson flattened = josson.getJosson("contact_info[0].flatten('.','[%d]')");

System.out.println("-- Keys --");
JsonNode node = flattened.getNode("keys()");
List<String> keys = new ArrayList<>();
node.elements().forEachRemaining(elem -> keys.add(elem.asText()));
keys.forEach(System.out::println);

System.out.println("-- Values --");
node = flattened.getNode("toArray()");
List<String> values = new ArrayList<>();
node.elements().forEachRemaining(elem -> values.add(elem.toString()));
values.forEach(System.out::println);

Output

-- Keys --
contact_id
contact_status.exam_status
contact_status.term_list[0].term_code
contact_status.term_list[0].t_list[0].s_code
contact_status.term_list[0].t_list[0].sexam_status
contact_status.term_list[0].t_list[1].s_code
contact_status.term_list[0].t_list[1].sexam_status
-- Values --
"Contact_001"
0
110
12001
0
13001
1

Query the keys and values in single array

JsonNode node = josson.getNode("contact_info[0].flatten('.','[%d]').entries().concat(key,' = ',value)");
List<String> keyValues = new ArrayList<>();
node.elements().forEachRemaining(elem -> keyValues.add(elem.asText()));
keyValues.forEach(System.out::println);

Output

contact_id = Contact_001
contact_status.exam_status = 0
contact_status.term_list[0].term_code = 110
contact_status.term_list[0].t_list[0].s_code = 12001
contact_status.term_list[0].t_list[0].sexam_status = 0
contact_status.term_list[0].t_list[1].s_code = 13001
contact_status.term_list[0].t_list[1].sexam_status = 1

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