How to get an object in a restful application?

Question

Java

Hello. Help, please, to solve a problem. I am writing a resful application. I return a list of objects from the main application

List<User> users = new ArrayList<>();
            Tariff tariff = tariffService.getTariffByTitle(contractTitle);

            for (Contract contract : contractService.getAll()) {
                if (contract.getTariff().equals(tariff)) {
                    contract.getUser().setPassword("");
                    users.add(contract.getUser());
                }
            }
        return users;

Now, in the rest I accept

String output = null;
        String URLstring = "http://localhost:8080/getRestInfo?contract=base";
        URL url = new URL(URLstring);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");
        conn.setRequestProperty("Accept", "application/json");
        conn.setRequestProperty("Authorization", "Basic " +
                new String(new Base64().encodeBase64("[email protected]:12345".getBytes())));
        if (conn.getResponseCode() != 200) {
            System.out.println("Failed : HTTP error code : "
                    + conn.getResponseCode());
            System.exit(1);
        }
        BufferedReader br = new BufferedReader(new InputStreamReader(
                (conn.getInputStream())));

        output = br.readLine();
        conn.disconnect();
        List<User> users = (List<User>) br;
        System.out.println(output);

But I get an exception that the byte stream cannot be cast to the list.
What is the correct way to accept objects in a restful application?

Answer 1

Try to do it on a spring RestTemplate as described here . An example of how to get List<User> usershere
PS

String output = null;
        String URLstring = "http://localhost:8080/getRestInfo?contract=base";
        URL url = new URL(URLstring);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");
        conn.setRequestProperty("Accept", "application/json");
        conn.setRequestProperty("Authorization", "Basic " +
                new String(new Base64().encodeBase64("[email protected]:12345".getBytes())));
        if (conn.getResponseCode() != 200) {
            System.out.println("Failed : HTTP error code : "
                    + conn.getResponseCode());
            System.exit(1);
        }
        BufferedReader br = new BufferedReader(new InputStreamReader(
                (conn.getInputStream())));

        output = br.readLine();

        /**
         * Здесь в output переменной у Вас в output лежит json, чтобы преобразовать его в java бины нужен парсер (это называется десериализовать), наиболее популярные - Gson или Jackson
         */
        Gson gson = new Gson();
        Type userListType = new TypeToken<ArrayList<User>>() {}.getType();
        List<User> users = gson.fromJson(output, userListType);

        conn.disconnect();
        System.out.println(output);