add record in json array in file

Question

I have an array of jsons like this

[
    {"submitted":"Bob","limit":0,"ID":123,"target":3},
    {"submitted":"Kate","limit":500,"ID":3221,"target":2}
 ]

I need to find a way how to insert a record into that file, without overwriting the file, or loading everything into memory

currently i'm doing it like this

 try (FileWriter file = new FileWriter("C:/test/output.json", true);
         BufferedWriter bfile = new BufferedWriter(file);
         PrintWriter outFile = new PrintWriter(bfile))
    {
        outFile.write(obj.toJSONString()+System.lineSeparator());
        outFile.flush();
    }
    catch (IOException e) {
        e.printStackTrace();
    }

Why you don't want to load all data to memory? As I see your data is very minimal. What prevents you to do? — Emre Savcı
– Emre Savcı, Commented Aug 28, 2018 at 18:50
@EmreSavcı it's just a sample; it has way more columns and rows, and I thought to make a temp solution until we get our DB ready — Vladimir Zaguzin
– Vladimir Zaguzin, Commented Aug 28, 2018 at 19:46

Emre Savcı · Accepted Answer · 2018-08-28 19:21:07Z

You can read and write json object&array using org.json as below. But I can't sure that editing a json file without reading it into memory could be possible.

package yourPackage;

import org.json.JSONArray;
import org.json.JSONObject;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class Main {
    public static void main(String[] args) throws IOException {
        JSONArray root = new JSONArray(new String(Files.readAllBytes(Paths.get("test.json"))));

        JSONObject obj = new JSONObject();
        obj.put("submitted","");
        obj.put("limit", 0);
        obj.put("ID", 123);
        obj.put("target", 3);

        root.put(obj);

        Files.write(Paths.get("test.json"), root.toString().getBytes());
    }
}

maven dependency of org.json :

    <!-- https://mvnrepository.com/artifact/org.json/json -->
    <dependency>
        <groupId>org.json</groupId>
        <artifactId>json</artifactId>
        <version>20180130</version>
    </dependency>

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