SMS REST API Quick start

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
// This example requires Gson configured in the build path (for JSON support):
// https://github.com/google/gson
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
public class Main {
    public static final String BASEURL = "http://app.gateway.smsend.it/API/v1.0/REST/";
    public static final String MESSAGE_HIGH_QUALITY = "N";
    public static final String MESSAGE_MEDIUM_QUALITY = "L";
    public static final String MESSAGE_LOW_QUALITY = "LL";
    public static void main(String[] args) {
        try {
            String[] authKeys = login("username", "password");
            SendSMSRequest sendSMS = new SendSMSRequest();
            sendSMS.setMessage("Hello world!");
            sendSMS.setMessageType(MESSAGE_HIGH_QUALITY);
            sendSMS.addRecipient("+39123456789");
            // Send it in 5 minutes!
            sendSMS.setScheduledDeliveryTime(new Date(System.currentTimeMillis() + (60000L * 5L)));
            sendSMS(authKeys, sendSMS);
        }
        catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    /* 
    * This object is used to create an SMS message sending request.
    * The JSon object is then automatically created
    * starting from an instance of this class, using GSon.
    */
    public static class SendSMSRequest {
        // The message body
        private String message;
        // The message type
        private String message_type = MESSAGE_HIGH_QUALITY;
        // Should the API return the remaining credits?
        private boolean returnCredits = false;
        // The list of recipients
        private List<String> recipient = new ArrayList<>();
        // The sender Alias (TPOA)
        private String sender = null;
        // Postpone the SMS message sending to the specified date
        private Date scheduled_delivery_time = null;
        public String getMessage() {
            return message;
        }
        public void setMessage(String message) {
            this.message = message;
        }
        public String getMessageType() {
            return message_type;
        }
        public void setMessageType(String messageType) {
            this.message_type = messageType;
        }
        public boolean isReturnCredits() {
            return returnCredits;
        }
        public void setReturnCredits(boolean returnCredits) {
            this.returnCredits = returnCredits;
        }
        public List<String> getRecipient() {
            return recipient;
        }
        public String getSender() {
            return sender;
        }
        public void setSender(String sender) {
            this.sender = sender;
        }
        public Date getScheduledDeliveryTime() {
            return scheduled_delivery_time;
        }
        public void setScheduledDeliveryTime(Date scheduled_delivery_time) {
            this.scheduled_delivery_time = scheduled_delivery_time;
        }
        public void addRecipient(String recipient) {
            this.recipient.add(recipient);
        }
    }
    
    /*
    * This class represents the API Response. 
    * It is automatically created starting from the JSON object
    * returned by the server, using GSon
    */
    public static class SendSMSResponse {
        private String result;
        private String order_id;
        private int total_sent;
        private int remaining_credits;
        private String internal_order_id;
        public String getResult() {
            return result;
        }
        public String getOrderId() {
            return order_id;
        }
        public int getTotalSent() {
            return total_sent;
        }
        public int getRemainingCredits() {
            return remaining_credits;
        }
        public String getInternalOrderId() {
            return internal_order_id;
        }
        public boolean isValid() {
            return "OK".equals(result);
        }
    }
    
    /*
    * Authenticates the user given it's username and password.
    * Returns the pair user_key, Session_key
    * @param username The user username
    * @param password The user password
    * @return A list with 2 strings. Index 0 is the user_key, index 1 is the Session_key
    * @throws IOException If an error occurs
    */
    private static String[] login(String username, String password) throws IOException {
        URL url = new URL(BASEURL + "/login?username=" + username + "&password=" + password);
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();
        conn.setRequestMethod("GET");
        if (conn.getResponseCode() != 200) {
            throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
        }
        BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String response = "";
        String output;
        while ((output = br.readLine()) != null) {
            response += output;
        }
        conn.disconnect();
        String[] parts = response.split(";");
        return parts;
    }

    /*
    * Sends an SMS message
    * @param authKeys The pair of user_key and Session_key
    * @param sendSMS The SendSMS object
    * @throws IOException If an error occurs
    */
    private static boolean sendSMS(String[] authKeys, SendSMSRequest sendSMS) throws IOException {
        GsonBuilder builder = new GsonBuilder();
        Gson gson = builder.create();

        URL url = new URL(BASEURL + "/sms");
        HttpURLConnection conn = (HttpURLConnection) url.openConnection();

        // Sending an SMS requires authentication
        conn.setRequestProperty("user_key", authKeys[0]);
        conn.setRequestProperty("Session_key", authKeys[1]);
        conn.setRequestMethod("POST");
        conn.setRequestProperty("Accept", "application/json");
        conn.setRequestProperty("Content-type", "application/json");
        conn.setDoOutput(true);

        String payload = gson.toJson(sendSMS);

        OutputStream os = conn.getOutputStream();
        os.write(payload.getBytes());
        os.flush();

        if (conn.getResponseCode() != 201) {
            throw new RuntimeException("Failed : HTTP error code : " + conn.getResponseCode());
        }

        BufferedReader br = new BufferedReader(new InputStreamReader(conn.getInputStream()));

        String response = "";
        String output;
        while ((output = br.readLine()) != null) {
            response += output;
        }
        conn.disconnect();

        SendSMSResponse responseObj = gson.fromJson(response, SendSMSResponse.class);

        return responseObj.isValid();
    }
}