Java: How do I create this JSON Array Structure using GSON

Question

I want to create a JSON array structure like this or append an object to the structure

{ "user" : [
     {"name" : "user1", "email": "user1@gmail"},
     {"name": "user2", "email": "user2@gmail"}
   ]
}

I'm using GSON to write this into a file

    public void appendToObject(File jsonFile, String key, String value)  {
        Objects.requireNonNull(jsonFile);
        Objects.requireNonNull(key);
        Objects.requireNonNull(value);
        if (jsonFile.isDirectory()) {
            throw new IllegalArgumentException("File can not be a directory!");
        }
        try {
            JsonObject node = readOrCreateNew(jsonFile);
            JsonArray userArray = new JsonArray();
            userArray.add(user(key,value));
            node.add("user", userArray);

           FileWriter writer = new FileWriter(jsonFile)
            gson.toJson(node, writer);


        }catch (Exception e)
        {
            Log.d("display1", "appendToObject: error"+e.getLocalizedMessage());
            e.printStackTrace();
        }
    }

private JsonObject user(String user, String password){
        JsonObject jsonObject = new JsonObject();
        jsonObject.addProperty("name", user);
        jsonObject.addProperty("password", password);
        return jsonObject;
    }

    private JsonObject readOrCreateNew(File jsonFile) throws IOException {
        if (jsonFile.exists() && jsonFile.length() > 0) {
            try (BufferedReader reader = new BufferedReader(new FileReader(jsonFile))) {
                return gson.fromJson(reader, JsonObject.class);
            }
        }
        return new JsonObject();
    }

       

Here's the code with suggestions integrated and with reading and writing JSON file functions

but im getting "user1":"{\\"values\\":[null,\\"user13\\",\\"useremail13\\"]}"}

how to structure it so that I get the desired output

Answer 1

I omitted some your code in appendToObject . But the meaning should be clear.

  public void appendToObject(File jsonFile, String key, String value)  {

    ...

    JsonObject node = readOrCreateNew(jsonFile);
  
    JsonObject newUser = user(key, value);
    JsonElement user = node.get("user");
    
    if (user != null && user.isJsonArray()){
      ((JsonArray) user).add(newUser);
    } else {
      JsonObject root = new JsonObject();
      node.add("user", createArray(newUser));
    }
     
    ...
  }

  private JsonObject createUserArray(JsonObject ... objects){
    JsonArray userArray = new JsonArray();
    for (JsonObject user : objects) {
      userArray.add(user);
    }
    return userArray;
  }

  private JsonObject user(String email, String name){
    JsonObject jsonObject = new JsonObject();
    jsonObject.addProperty("name", name);
    jsonObject.addProperty("email", email);
    return jsonObject;
  }