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How to get access token from Spotify API? [java]

I am fairly new to programming with Java but am interested in creating a program that allows for connection to the Spotify API. I am using the Client Credential Flow authorization process but keep getting java.io.IOException: insufficient data written exception when trying to reach the access token. I cannot figure out what information I am missing to complete the request.
I found a YouTube video of the same process being completed in Python and they utilized the requests feature and .json() to receive the access token. Is there a similar way to complete this in Java?
try {
String str = "application/x-www-form-urlencoded";
byte[] hold = str.getBytes();
//create url
URL url = new URL(tokenURL);
//open connection to url
conn = (HttpURLConnection) url.openConnection();
conn.setDoOutput(true);
conn.setDoInput(true);
//setup post headers and body
conn.setRequestMethod("POST");
conn.setFixedLengthStreamingMode(32);
conn.setRequestProperty("Authorization",String.format("Basic %s", clientCredEncode));
conn.setRequestProperty("grant_type", "client_credentials");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty("user-agent", "Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/45.0.2454.85 Safari/537.36");
//validate connection
int val = conn.getResponseCode();
String response = conn.getResponseMessage();
System.out.println("response code: " + val);
System.out.println("response: " + response);
}catch(Exception e){
System.out.println("error: " + e);
conn.disconnect();
}
PYTHON CODE
This code performs the action in python.
def spotifyAuth(clientID, clientSecret):
clientCred = f"{clientID}:{clientSecret}"
encodedClient = base64.b64encode(clientCred.encode())
tokenURL = "https://accounts.spotify.com/api/token"
method = "POST"
tokenData = {"grant_type" : "client_credentials"}
tokenHeader = {"Authorization" : f"Basic {encodedClient.decode()}"}
r = requests.post(tokenURL, data=tokenData, headers=tokenHeader)
tokenResponse = r.json()
accessToken = tokenResponse['access_token']
expires = tokenResponse['expires_in']
return accessToken, expires

Thanks to Rup I was able to identify the issue. I was not properly sending anything with the POST. I added .getOutputStream() so send the request and .getInputStream() to receive the response.
//create url access point
URL url = new URL(tokenURL);
//open http connection to url
conn = (HttpURLConnection) url.openConnection();
conn.setDoOutput(true);
conn.setDoInput(true);
//setup post function and request headers
conn.setRequestMethod("POST");
conn.setRequestProperty("Authorization",String.format("Basic %s", clientCredEncode));
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
//set body for posting
String body = "grant_type=client_credentials";
//calculate and set content length
byte[] out = body.getBytes(StandardCharsets.UTF_8);
int length = out.length;
conn.setFixedLengthStreamingMode(length);
//connect to http
conn.connect();
//}
//send bytes to spotify
try(OutputStream os = conn.getOutputStream()) {
os.write(out);
}
//receive access token
InputStream result = conn.getInputStream();
s = new String(result.readAllBytes());
//System.out.println(s);

For anyone whos looking for the same, Here's a better one
import com.google.gson.JsonParser;
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
public class SpotifyToken {
public String accessToken = "";
public String expiresIn = "";
public void get() throws IOException {
URL url = new URL(Endpoints.TOKEN);
HttpURLConnection http = (HttpURLConnection) url.openConnection();
http.setRequestMethod("POST");
http.setDoOutput(true);
http.setRequestProperty("content-type", "application/x-www-form-urlencoded");
String data = "grant_type=client_credentials&client_id=" + Endpoints.CLIENT_ID + "&client_secret=" + Endpoints.CLIENT_SECRET + "";
byte[] out = data.getBytes(StandardCharsets.UTF_8);
OutputStream stream = http.getOutputStream();
stream.write(out);
BufferedReader Lines = new BufferedReader(new InputStreamReader(http.getInputStream()));
String currentLine = Lines.readLine();
StringBuilder response = new StringBuilder();
while (currentLine != null) {
response.append(currentLine).append("\n");
currentLine = Lines.readLine();
}
this.accessToken = String.valueOf(JsonParser.parseString(String.valueOf(response)).getAsJsonObject().getAsJsonObject("access_token"));
this.expiresIn = String.valueOf(JsonParser.parseString(String.valueOf(response)).getAsJsonObject().getAsJsonObject("expires_in"));
http.disconnect();
}
}
The class Endpoints.java will be
public class Endpoints {
public static final String CLIENT_ID = "YOUR_CLIENT_ID";
public static final String CLIENT_SECRET = "YOUR_CLIENT_SECRET";
public static final String TOKEN = "https://accounts.spotify.com/api/token";
}
If it interests you, here is the cURL command for the same:
curl --request POST \
--url 'https://accounts.spotify.com/api/token' \
--header 'content-type: application/x-www-form-urlencoded' \
--data grant_type=client_credentials \
--data client_id=YOUR_CLIENT_ID \
--data client_secret=YOUR_CLIENT_SECRET \
I used this tool to convert cURL to java code.

Java USES HTTP v1 to send Chinese notifications that are error characters

The request header is the same as the official document. Why did android receive the wrong character when I used Chinese? Using English is correct
private HttpURLConnection getConnections() throws IOException {
URL url = new URL(BASE_URL + FCM_SEND_ENDPOINT);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestProperty("Authorization", "Bearer " + getAccessTokens());
httpURLConnection.setRequestProperty("Content-Type", "application/json; UTF-8");
return httpURLConnection;
}

Google Firebase HTTP Post

I'm trying to request POST for Google Firebase in server. I followed the document guideline, but it has not worked.
My sending message function is following thing.
private static void sendMsg() throws IOException
{
String url = "https://fcm.googleapis.com/fcm/send";
URL obj = new URL(url);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("POST");
con.setRequestProperty("Content-Type", "application/json");
con.setRequestProperty("Authorization", "key=XXXX");
JSONObject msg=new JSONObject();
msg.put("message","test8");
JSONObject parent=new JSONObject();
parent.put("to", "XXXXX");
parent.put("data", msg);
con.setDoOutput(true);
int responseCode = con.getResponseCode();
System.out.println("\nSending 'POST' request to URL : " + url);
System.out.println("Post parameters : " + parent.toString());
System.out.println("Response Code : " + responseCode+" "+con.getResponseMessage());
}
The response code is "411" and the message is "Length Required".
I also tried to set the content length, but the result was same.
Am I doing wrong?

You have all the setup right but are not writing the data. Add the statements shown:
con.setDoOutput(true);
// Added
OutputStreamWriter os = new OutputStreamWriter(con.getOutputStream());
os.write(parent.toString());
os.flush();
os.close();

GCM Push Notifications are not delivered to devices

We (Panos and Rainer - see the comments down) have a server and several Android devices.
We want to send push notifications from our server via GCM to the Android devices.
Now we make a post request to the GCM server. The GCM server response is that all is fine (success==1 and even the message-id)!
BUT the push notification(s) are never delivered to the devices.
If we use the same data and the Chrome addon Postman - the notifications are delivered immediately.
We tried all lot of different solutions. We get always the feedback of the GCM server that all is ok - but the push notifications aren't send.
We also tried this one:
https://github.com/googlesamples/google-services/blob/master/android/gcm/gcmsender/src/main/java/gcm/play/android/samples/com/gcmsender/GcmSender.java

You might also post the URL you use. There is a new GCM enpoint which looks like the following:
https://gcm-http.googleapis.com/gcm/send
I am not yet sure what's causing the issues on your side. But the following is tested and working:
public class Main {
public static void main(String[] args) {
// write your code here
try {
String url = "https://gcm-http.googleapis.com/gcm/send";
URL obj = new URL(url);
HttpsURLConnectionImpl conn = (HttpsURLConnectionImpl) obj.openConnection();
conn.setRequestProperty("Content-Type", "application/json");
conn.setDoOutput(true);
conn.setRequestMethod("POST");
conn.setRequestProperty ("Authorization", "key=***");
String title = "Short title";
String body = "A body :D";
String token = "****";
String data = "{ \"notification\": { \"title\": \"" + title +"\", \"body\": \"" + body + "\" }, \"to\" : \"" + token + "\", \"priority\" : \"high\" }";
OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream());
out.write(data);
out.close();
String text = getText(new InputStreamReader(conn.getInputStream()));
System.out.println(text);
} catch (Exception e) {
e.printStackTrace();
}
}
public static String getText(InputStreamReader in) throws IOException {
StringBuilder sb=new StringBuilder();
BufferedReader br = new BufferedReader(in);
String read;
while((read=br.readLine()) != null) {
sb.append(read);
}
br.close();
return sb.toString();
}
}

This is the data used for the Postman request which is working without any problem.
Rainer already mentioned that we tried several implementations on the Java side and it seems that we are always able to communicate with the service and receive a response which seems to look correct so far:
{
"multicast_id":7456542468425129822,
"success":1,
"failure":0,
"canonical_ids":0,
"results":
[{
"message_id":"0:1457548597263237%39c590d7f9fd7ecd"
}]
}

Not sure if I'm on the right track but do you mean downstream HTTP messages (plain text)?
Tried to send the following JSON to the service (from Postman) which results again in a positive response but this time the notification did not reach the device (just to make that clear, at the moment there is no app on the device listening actively for incoming notifications -> first of all we just want to ensure that they generally arrive on the device):
{
"data":
{
"score": "5x1",
"time": "15:10"
},
"to" : "SECRET-DEVICE-TOKEN"
}

Thanks to all of you trying to help here but to be honest, this issue is really frustrating. Communicating with an interface\service which seems not to be able to return a useful response in case the request contains maybe evil stuff which will finally prevent GCM from sending the push notification to the device, feels like a pain in the ass. If Postman would also fail I would say ok, you can not be so stupid :-)
Here are some quick'n dirty implementations we have already used.
Example
try
{
URL url = new URL(apiUrl);
HttpsURLConnection conn = (HttpsURLConnection);//also tried HttpURLConnection
url.openConnection();
conn.setDoOutput(true);
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/json");
conn.setRequestProperty("Authorization", "key="+apiKey);
conn.setDoOutput(true);
String json = "{\"priority\":\"high\",\"notification\":{\"title\":\"Some title\",\"text\":\"Some text\"},\"to\":\""+deviceToken+"\"}";
OutputStream os = conn.getOutputStream();
os.write(json.getBytes());
os.flush();
}
catch(Exception exc)
{
System.out.println("Error while trying to send push notification: "+exc);
}
Example
HttpClient httpClient = HttpClientBuilder.create().build();
try
{
HttpPost request = new HttpPost(apiUrl);
StringEntity params =new StringEntity("{\"priority\":\"high\",\"notification\":{\title\":\"Some title\",\"text\":\"Some text\"},\"to\":\""+deviceToken+"\"}");
request.addHeader("Content-Type", "application/json");
request.addHeader("Authorization", "key="+apiKey);
request.setEntity(params);
HttpResponse response = httpClient.execute(request);
// check response
System.out.println(response.getStatusLine().toString());
}catch (Exception exc) {
System.out.println("Error while trying to send push notification: "+exc);
} finally {
httpClient.getConnectionManager().shutdown(); //Deprecated
}
Example
try
{
String charset = "UTF-8";
URLConnection connection = new URL(apiUrl).openConnection();
connection.setDoOutput(true);
connection.setRequestProperty("Accept-Charset", charset);
connection.setRequestProperty("Content-Type", "application/json;charset=" + charset);
connection.setRequestProperty("Authorization", "key="+apiKey);
String param = "{\"priority\":\"high\",\"notification\":{\"title\":\"Some title\",\"text\":\"Some text\"},\"to\":\""+deviceToken+"\"}";
try (OutputStream output = connection.getOutputStream())
{
output.write(param.getBytes(charset));
}
InputStream response = connection.getInputStream();
}
catch(Exception exc)
{
System.out.println("Error while trying to send push notification: "+exc);
}
Example
try
{
// prepare JSON
JSONObject jGcmData = new JSONObject();
JSONObject jData = new JSONObject();
jData.put("message", "{ \"data\": {\"score\": \"5x1\",\"time\": \"15:10\"},\"to\" : \""+deviceToken+"\"}");
jGcmData.put("to", deviceToken);
jGcmData.put("data", jData);
// Create connection to send GCM Message request.
URL url = new URL("https://android.googleapis.com/gcm/send");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setRequestProperty("Authorization", "key=" + apiKey);
conn.setRequestProperty("Content-Type", "application/json");
conn.setRequestMethod("POST");
conn.setDoOutput(true);
// Send GCM message content.
OutputStream outputStream = conn.getOutputStream();
outputStream.write(jGcmData.toString().getBytes());
// Read GCM response.
InputStream inputStream = conn.getInputStream();
String resp = IOUtils.toString(inputStream);
System.out.println(resp);
} catch (IOException e) {
System.out.println("Unable to send GCM message. "+e);
}

Mike, with your example it's working also on our side. After comparing your implementation with the on eon our side, the only real difference I found is the used URL!!
Somehow the URL used in our Java implementation was https://android.googleapis.com/gcm/send
Seems that https://gcm-http.googleapis.com/gcm/send is the right one which by the way was also used for our Postman tests.
But why on hell is the URL from our failed tests still somehowe valid and returns a response!?

Setting the priority to high in the json resolved the issue for me.
'registration_ids' => $id,
'priority' => 'high',
'data' => $load

For our case, the clients Android devices had intermittent internet connection issue, that is, network dropouts thus causing notification delivery failed. We resolved the reliability issue with the following JAVA GCM code:
gcmPayload.setTime_to_live(messageExpiryTime); //in seconds. Set notification message expiry to give user time to receive it in case they have intermittent internet connection, or phone was off
gcmPayload.setPriority("high");
and APNS code:
ApnsService apnsService = APNS.newService().withCert(certificateStream, configurations.getApnPassword()).withProductionDestination().build();
PayloadBuilder payloadBuilder = APNS.newPayload();
...
payloadBuilder.instantDeliveryOrSilentNotification(); //same as content-available=true
String payload = payloadBuilder.build();
Integer now = (int)(new Date().getTime()/1000);
//use EnhancedApnsNotification to set message expiry time
for(String deviceToken : deviceTokens) {
EnhancedApnsNotification notification = new EnhancedApnsNotification(EnhancedApnsNotification.INCREMENT_ID() /* Next ID */,
now + messageExpiryTime /* Expiry time in seconds */,
deviceToken /* Device Token */,
payload);
apnsService.push(notification);
}
Also, remember to consider time zone if your backend server time is different to the client mobile app time.

code 400 error on post call with android

I am trying to call a WS method from an Android application with POST method.
What I have done:
String urlServer = GlobalSession.IP + "insert_reportByte";
Log.d("[Report]", "url address: " + urlServer);
URL url = new URL(urlServer);
HttpURLConnection connection = (HttpURLConnection) url
.openConnection();
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setUseCaches(false);
connection.setRequestMethod("POST");
connection.setRequestProperty("Connection", "Keep-Alive");
connection.setRequestProperty("Content-Type",
"multipart/form-data");
DataOutputStream outputStream = new DataOutputStream(
connection.getOutputStream());
outputStream.write(outputByteArray, 0, outputByteArray.length);
int serverResponseCode = connection.getResponseCode();
String serverResponseMessage = connection.getResponseMessage();
Log.d("ServerCode", "" + serverResponseCode);
Log.d("serverResponseMessage", "" + serverResponseMessage);
outputStream.flush();
outputStream.close();
} catch (Exception ex) {
// ex.printStackTrace();
Log.e("[Report] --- /!\\ Error: ", ex.getMessage());
}
return result;
So I am supposed to send a byte array to the service. But I have a 400 error response. My question is: how to get the details of such an issue? Because I cannot find anything in the logs of the server and it's hard to debug if I do not have the details...
The WS is defined (in ASP.NET) that way:
[OperationContract]
[WebInvoke(Method = "POST",
UriTemplate = "insert_reportByte",
BodyStyle = WebMessageBodyStyle.Bare)]
void insert_reportByte(byte[] image);
And the called method is the following
public void insert_reportByte(byte[] image)
{
MyEntities entities = new MyEntities();
String base64stringimage = System.Convert.ToBase64String(image,0,image.Length);
entities.insert_report("admin", "0614141.107346.2001", "test", base64stringimage, "test");
}
What did I do wrong?
Thank you !

You should change the uploadReadAheadSize and maxReceivedMessageSize parameters on your server applicationHost.config file.
Here you´ve got a thread that talks about it
http://forums.iis.net/t/1169257.aspx?Request+Entity+Too+large+413+error+
This link might be useful too as it explains why you should change the uploadReadAheadSize and maxReceivedMessageSize parameters for better handling of file uploads.
http://www.codeproject.com/Articles/521725/413-Request-Entity-Too-Large
UPDATE
Try using this library for the http calls. It seems that you're sending a bad request to the server. I don't think it has something to do with the parameters that the ws expects but the http headers sent by the android app.
https://github.com/loopj/android-async-http
Hope it helps. :)