Receive token and verify on SP gateway

VerifyToken.java

package co.enoobong.rotimiphotography.backend;


import org.json.JSONException;
import org.json.JSONObject;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Map;
import java.util.logging.Logger;

import javax.annotation.Nonnull;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.xml.bind.DatatypeConverter;

import static com.google.api.client.http.HttpMethods.POST;
import static org.apache.http.HttpHeaders.AUTHORIZATION;
import static org.apache.http.HttpHeaders.CONTENT_TYPE;

public class VerifyToken extends HttpServlet {
    private static final String API_KEY = "test_pr_d6c3cb5a5b7944e1ad5bc1164f853449" + ":";
    private static final Logger log = Logger.getLogger(VerifyToken.class.getName());

    @Override
    public void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        resp.setContentType("text/plain");
        String token = req.getParameter("token");
        String price = req.getParameter("price");
        String currency = req.getParameter("currency");

        try{
            //Build name data request params
            JSONObject jsonRequest = new JSONObject();
            jsonRequest.put("token", token);
            jsonRequest.put("amount", Integer.parseInt(price));
            jsonRequest.put("amount_currency", currency);
            log.info(jsonRequest.toString());

            //Prepare and Execute HTTP Post
            URL url = new URL("https://api.simplepay.ng/v1/payments/verify");
            String basicAuth = "Basic " + DatatypeConverter.printBase64Binary(API_KEY.getBytes());
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod(POST);
            httpURLConnection.setRequestProperty(AUTHORIZATION, basicAuth);
            httpURLConnection.setRequestProperty(CONTENT_TYPE, "application/json");
            httpURLConnection.setUseCaches(false);
            httpURLConnection.setDoInput(true);
            httpURLConnection.setDoOutput(true);

            OutputStream outputStream = httpURLConnection.getOutputStream();
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
            writer.write(jsonRequest.toString());
            writer.flush();
            writer.close();
            outputStream.close();
            httpURLConnection.connect();

            //Read response
            int statusCode =httpURLConnection.getResponseCode();
            BufferedReader reader = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream()));
            JSONObject jsonResponse = readJsonFromReader(reader);
            log.info(jsonResponse.toString());
            int responseCode = jsonResponse.getInt("response_code");

            //Verify transaction
            if (statusCode == HttpURLConnection.HTTP_OK) {
                if(responseCode == 20000){
                    //Transaction successful do something
                    resp.getWriter().println("Transaction Successful");
                } else {
                    //transaction failed
                    resp.getWriter().println("Transaction unsuccessful " + responseCode);
                }
            } else {
                //transaction failed
                resp.getWriter().println("Transaction unsuccessful " + responseCode);
            }
        } catch (Exception e) {
            resp.getWriter().println(e.getMessage());
            System.err.println(e.getMessage());
        }
    }

    private JSONObject readJsonFromReader(Reader reader) throws IOException, JSONException {
        try{
            StringBuilder sb = new StringBuilder();
            int cp;
            while ((cp = reader.read()) != -1) {
                sb.append((char) cp);
            }
            String jsonText = sb.toString();
            return new JSONObject(jsonText);
        } finally {
            reader.close();
        }
    }

}