Gson Library Write in the file and only change a specific value

Question

I'm currently using the Gson library to write/read a .json file. I have this method to write intro the json.

    public static void write(String key, String value){
    GeneralJsonConfig gjc = new GeneralJsonConfig();
    if(key.equals("testKey")){
        gjc.setaucString(value);
    }
    Gson gson = new Gson();
    String json = gson.toJson(gjc);
    try{
    FileWriter fw = new FileWriter(launcherConfigFile);
    fw.write(json);
    fw.close();
    } catch(IOException e) {

    }
}

But lets say i have this .json:

{"testKey": "some test", "testKey2": "test 3"}

and i only want to change the thestKey from "some test" to another text and the other key/values will remain as they are now, but with my method the other values/key just dissaper, how can i solve this to make the other key/values stay ?

Update: Found an answer based on sam100rav answer, i simply read the complete json file to get the vaules and then write them again with the changed that i want done:

public static void write(String key, String value){
        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        try{
            BufferedReader br = new BufferedReader(new FileReader(launcherConfigFile));
            GeneralJsonConfig gjcObject = gson.fromJson(br, GeneralJsonConfig.class);
    if(key.equals("testKey")){
        gjc.setaucString(value);
    }
            String json = gson.toJson(gjcObject);
            FileWriter fw = new FileWriter(launcherConfigFile);
            fw.write(json);
            fw.close();
            br.close();
        } catch (IOException e){
            main.er.LogError("23", "");
        }

sam100rav · Accepted Answer · 2015-07-18 19:34:03Z

1

JSONObject obj = new JSONObject();
obj.put("testKey", "some test");
obj.put("testKey2", "test 3");
if(key.equals("testKey")){
        obj.put("testKey", value);
    }
    String json = obj.toString();
    try{
    FileWriter fw = new FileWriter(launcherConfigFile);
    fw.write(json);
    fw.close();
    }

answered Jul 18, 2015 at 19:34

sam100rav

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Comments

peti446 · Accepted Answer · 2019-06-19 23:15:22Z

Found an answer based on sam100rav answer, i simply read the complete json file to get the vaules and then write them again with the changed that i want done:

public static void write(String key, String value){
        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        try{
            BufferedReader br = new BufferedReader(new FileReader(launcherConfigFile));
            GeneralJsonConfig gjcObject = gson.fromJson(br, GeneralJsonConfig.class);
    if(key.equals("testKey")){
        gjc.setaucString(value);
    }
            String json = gson.toJson(gjcObject);
            FileWriter fw = new FileWriter(launcherConfigFile);
            fw.write(json);
            fw.close();
            br.close();
        } catch (IOException e){
            main.er.LogError("23", "");
        }

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