ICDAPIclient.java

import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder; 
import javax.net.ssl.HttpsURLConnection;

import org.json.*;

public class ICDAPIclient {

	private final String TOKEN_ENPOINT = "https://icdaccessmanagement.who.int/connect/token";
	private final String CLIENT_ID = "...";
	private final String CLIENT_SECRET = "...";
	private final String SCOPE = "icdapi_access";
	private final String GRANT_TYPE = "client_credentials";


	public static void main(String[] args) throws Exception {

		String uri = "https://id.who.int/icd/entity";

		ICDAPIclient api = new ICDAPIclient();
		String token = api.getToken();
		System.out.println("URI Response JSON : \n" + api.getURI(token, uri));
	}


	// get the OAUTH2 token
	private String getToken() throws Exception {

		System.out.println("Getting token...");

		URL url = new URL(TOKEN_ENPOINT);
		HttpsURLConnection con = (HttpsURLConnection) url.openConnection();
		con.setRequestMethod("POST");

		// set parameters to post
		String urlParameters =
        		"client_id=" + URLEncoder.encode(CLIENT_ID, "UTF-8") +
        		"&client_secret=" + URLEncoder.encode(CLIENT_SECRET, "UTF-8") +
			"&scope=" + URLEncoder.encode(SCOPE, "UTF-8") +
			"&grant_type=" + URLEncoder.encode(GRANT_TYPE, "UTF-8");
		con.setDoOutput(true);
		DataOutputStream wr = new DataOutputStream(con.getOutputStream());
		wr.writeBytes(urlParameters);
		wr.flush();
		wr.close();

		// response
		int responseCode = con.getResponseCode();
		System.out.println("Token Response Code : " + responseCode + "\n");

		BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
		String inputLine;
		StringBuffer response = new StringBuffer();
		while ((inputLine = in.readLine()) != null) {
			response.append(inputLine);
		}
		in.close();

		// parse JSON response
		JSONObject jsonObj = new JSONObject(response.toString());
		return jsonObj.getString("access_token");
	}


	// access ICD API
	private String getURI(String token, String uri) throws Exception {

		System.out.println("Getting URI...");

		URL url = new URL(uri);
		HttpURLConnection con = (HttpURLConnection) url.openConnection();
		con.setRequestMethod("GET");

		// HTTP header fields to set
		con.setRequestProperty("Authorization", "Bearer "+token);
		con.setRequestProperty("Accept", "application/json");
		con.setRequestProperty("Accept-Language", "en");
		con.setRequestProperty("API-Version", "v2");

		// response
		int responseCode = con.getResponseCode();
		System.out.println("URI Response Code : " + responseCode + "\n");

		BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
		String inputLine;
		StringBuffer response = new StringBuffer();
		while ((inputLine = in.readLine()) != null) {
			response.append(inputLine);
		}
		in.close();

		return response.toString();
	}

}