How to parse json using hhtpUrlConnection?

Question

Java

The link https://jsonplaceholder.typicode.com/posts
contains json, My task is to parse json in which an array of objects, then convert it to classes and print it. What am I doing wrong here?

the code:

public static void main(String[] args) {
    Gson gson = new GsonBuilder()
            .setPrettyPrinting()
            .create();

    String url = "https://jsonplaceholder.typicode.com/posts";
    try {
        HttpURLConnection httpClient = (HttpURLConnection) new URL(url).openConnection();
        httpClient.setRequestMethod("GET");
        httpClient.setRequestProperty("User", "Google Ghrome");
        int responseCode = httpClient.getResponseCode();
        System.out.println("URL сайта: " + url);
        System.out.println("код ответа: " + responseCode);

        BufferedReader in = new BufferedReader(new InputStreamReader(httpClient.getInputStream()));
        

        User[]  users = gson.fromJson(in, User[].class);
        System.out.println(users);
    } catch (IOException e) {
        e.printStackTrace();
    }
}

thanks in advance!
p.s. I googled, but I didn't find anything clear (((

Answer 1

Thus, I parse information from the tax database. Works great. Modify and create objects.

public static HashMap <String,String> sendRequestByContractorInformation (String request){
        HashMap <String,String> contractorInfo = new HashMap<>();
        final String KEY = "ключ";
        String URL = "https://api-fns.ru/api/egr?req=".concat(request).concat("&key=").concat(KEY);
        final String METHOD = "GET";
        try {
            HttpURLConnection connection = (HttpURLConnection) new URL(URL).openConnection();
            connection.setRequestMethod(METHOD);
            connection.connect();
            JSONObject jsonObject;
            int status = connection.getResponseCode();
            if (status == HttpURLConnection.HTTP_OK) {
                InputStream in = connection.getInputStream();
                jsonObject = new JSONObject(IOUtils.toString(in)); // здесь получаем JSON
                JSONArray jsonArrayItems = (JSONArray) jsonObject.get("items");
                Iterator jsonArrayItemsIterator = jsonArrayItems.iterator();
                while (jsonArrayItemsIterator.hasNext()){
                    JSONObject element = (JSONObject) jsonArrayItemsIterator.next();
                    System.out.println(element);
                    if (element.has("ЮЛ")){ // проверяем, есть ли JSON c нужным ключом и делаем с ним, то что нам надо!!!
                        System.out.println("JSON с ключом <ЮЛ> присутствует");
                        JSONObject jsonObjectUL = new JSONObject(element.getJSONObject("ЮЛ").toString());
                        System.out.println(jsonObjectUL);
                        if (jsonObjectUL.has(CONTRACTOR_INFO.FULL_NAME.getValue())){
                            System.out.println("JSON с ключом <"+CONTRACTOR_INFO.FULL_NAME.getValue()+"> присутствует");
                            contractorInfo.put(CONTRACTOR_INFO.FULL_NAME.name(),jsonObjectUL.getString(CONTRACTOR_INFO.FULL_NAME.getValue()));
                        } else {
                            System.out.println("JSON с ключом <"+CONTRACTOR_INFO.FULL_NAME.getValue()+"> ОТСУТСТВУЕТ!!!");
                            contractorInfo.put(CONTRACTOR_INFO.FULL_NAME.name(),"Нет данных");
                        }
                        System.out.println("Добавлена запись: " + (CONTRACTOR_INFO.FULL_NAME.name() + "=" + contractorInfo.get(CONTRACTOR_INFO.FULL_NAME.name())));
                    }
                }
                in.close();
                connection.disconnect();
            } else {
                System.out.println("Соединение с сервером не установлено... Попробуйте повторить операцию позднее.");
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return contractorInfo;
    }