How to get the key count from a JSON file using Java?

Question

I want to get the number of properties in the rowdata element, in the example JSON below:

    "rowData": [
          {
           "_idName": "CONFIG_DATA_ENTITY_MAP.CONFIG_DT_ENTITY_MAP_ID",
           "ERROR": null,
           "_id": 1,
           "ENTITY_TYPE": "BASE_TIMESERIES",
           "DATA_TYPE": "Date",
           "FIX_THIS": 0,
           "ENTITY_NAME": "ASP",
           "SOURCE_TABLE_COLUMN": "AS_OF_DATE"
          },
          {
           "_idName": "CONFIG_DATA_ENTITY_MAP.CONFIG_DT_ENTITY_MAP_ID",
           "ERROR": null,
           "_id": 2,
           "ENTITY_TYPE": "BASE_TIMESERIES",
           "DATA_TYPE": "String",
           "FIX_THIS": 0,
           "ENTITY_NAME": "ASP",
           "SOURCE_TABLE_COLUMN": "CUSTOMER_ID"
          }
    ]

Perhaps you are looking for this https://stackoverflow.com/questions/2591098/how-to-parse-json-in-java — Ezio, Mar 02 '21 at 17:34
Taking your question literally, "rowdata element count" is 2. There are 2 elements in the rowdata array. If you mean you want to get the number properties in each element, what if the first element has 8 properties and the second element has 9? — k314159, Mar 02 '21 at 17:36
for now its 8 only ,if one get resolved we can think of other — , Mar 02 '21 at 17:42

score 2 · Answer 1 · edited Mar 02 '21 at 18:42

Have you tried converting into JSONObject and use jsonObject.length()?

Here's the rough code:

public static void main(String[] args) {
     String jsonData = "{\"rowData\": [\n" +
            "      {\n" +
            "       \"_idName\": \"CONFIG_DATA_ENTITY_MAP.CONFIG_DT_ENTITY_MAP_ID\",\n" +
            "       \"ERROR\": null,\n" +
            "       \"_id\": 1,\n" +
            "       \"ENTITY_TYPE\": \"BASE_TIMESERIES\",\n" +
            "       \"DATA_TYPE\": \"Date\",\n" +
            "       \"FIX_THIS\": 0,\n" +
            "       \"ENTITY_NAME\": \"ASP\",\n" +
            "       \"SOURCE_TABLE_COLUMN\": \"AS_OF_DATE\"\n" +
            "      },\n" +
            "      {\n" +
            "     \"_idName\": \"CONFIG_DATA_ENTITY_MAP.CONFIG_DT_ENTITY_MAP_ID\",\n" +
            "     \"ERROR\": null,\n" +
            "     \"_id\": 2,\n" +
            "     \"ENTITY_TYPE\": \"BASE_TIMESERIES\",\n" +
            "     \"DATA_TYPE\": \"String\",\n" +
            "     \"FIX_THIS\": 0,\n" +
            "     \"ENTITY_NAME\": \"ASP\",\n" +
            "     \"SOURCE_TABLE_COLUMN\": \"CUSTOMER_ID\"\n" +
            "  }\n" +
            "]}";
     try {
        JSONObject jsonObject = new JSONObject(jsonData.replace("\n", ""));
        JSONArray jsonArray = jsonObject.getJSONArray("rowData");
        for (int i = 0; i < jsonArray.length(); i++) {
            JSONObject temp = jsonArray.getJSONObject(i);
            System.out.println("temp = " + temp.length());
        }
    } catch (JSONException err){
        Log.d("Error", err.toString());
    }
}

score 0 · Answer 2 · answered Mar 02 '21 at 17:48

0

Convert you JSON to Object. Pass it to your controller and read the size of it

@RequestBody Map<String, Object> objectMap

objectMap.size()

answered Mar 02 '21 at 17:48

Amit

633
6
13

score 0 · Answer 3 · answered Mar 02 '21 at 18:22

A raw solution without exception handling. I use the library 'org.json' and had to wrap your raw String inside braces to make it json compatible:

  final String jsonString = "{\"rowData\": [\n"
  + "      {\n"
  + "       \"_idName\": \"CONFIG_DATA_ENTITY_MAP.CONFIG_DT_ENTITY_MAP_ID\",\n"
  + "       \"ERROR\": null,\n"
  + "       \"_id\": 1,\n"
  + "       \"ENTITY_TYPE\": \"BASE_TIMESERIES\",\n"
  + "       \"DATA_TYPE\": \"Date\",\n"
  + "       \"FIX_THIS\": 0,\n"
  + "       \"ENTITY_NAME\": \"ASP\",\n"
  + "       \"SOURCE_TABLE_COLUMN\": \"AS_OF_DATE\"\n"
  + "      },\n"
  + "      {\n"
  + "     \"_idName\": \"CONFIG_DATA_ENTITY_MAP.CONFIG_DT_ENTITY_MAP_ID\",\n"
  + "     \"ERROR\": null,\n"
  + "     \"_id\": 2,\n"
  + "     \"ENTITY_TYPE\": \"BASE_TIMESERIES\",\n"
  + "     \"DATA_TYPE\": \"String\",\n"
  + "     \"FIX_THIS\": 0,\n"
  + "     \"ENTITY_NAME\": \"ASP\",\n"
  + "     \"SOURCE_TABLE_COLUMN\": \"CUSTOMER_ID\"\n"
  + "  }\n"
  + "]}";

public int numberOfChildElement(String data, int elementIndex){
  JSONObject jsonObject = new JSONObject(data);
  JSONArray jsonArray = jsonObject.getJSONArray("rowData");
  return jsonArray.getJSONObject(elementIndex).length();
}

So if you call the method 'numberOfChildElement' passing in the raw String and the index of the element you want to get the count of (0 or 1 in your example), you should get the result you want.

score 0 · Answer 4 · answered Mar 03 '21 at 03:06

    package com.example.demo;
    
    import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Paths;
    
    import org.json.JSONArray;
    import org.json.JSONException;
    import org.json.JSONObject;
    import org.json.simple.parser.ParseException;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    
    public class ColumnDefValidator {
    
    
        public static void columnDef(JSONObject jsonObjects) {
        int templengthColumn = 0;
        int templelenghtRow = 0;
        try {
            JSONArray columnDefsData = jsonObjects.getJSONArray("columnDefs");
            JSONArray rowDataDefs = jsonObjects.getJSONArray("rowData");
            for (int i = 0; i < columnDefsData.length(); i++) {
                JSONObject temp = columnDefsData.getJSONObject(i);
                templengthColumn = temp.length();
            }
            for (int i = 0; i < rowDataDefs.length(); i++) {
                JSONObject temp = rowDataDefs.getJSONObject(i);
                templelenghtRow = temp.length();
            }

            System.out.println(templengthColumn);
            System.out.println(templelenghtRow);
        } catch (JSONException err) {
            System.out.println(err.toString());
        }
    }

    public static JSONObject parseJSONFile(String filename) throws JSONException, IOException {
        String content = new String(Files.readAllBytes(Paths.get(filename)));
        return new JSONObject(content);
    }

    public static void main(String[] args) throws IOException, JSONException, ParseException {
        String filename = "/home/niteshb/WaveProject/working_dir/jsonoutput/aggrid/resp_attribute_report.json";
        JSONObject jsonObject = parseJSONFile(filename);
        columnDef(jsonObject);

    }
}

How to get the key count from a JSON file using Java?

4 Answers4