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Calling Post request without body in java

I have a post API which doesn't accept any input. I have to get output from API. But it is giving compilation error.
HttpURLConnection connection = null;
String targetUrl="https://idcs-oda-9417f93560b94eb8a2e2a4c9aac9a3ff-t0.data.digitalassistant.oci.oc-test.com/api/v1/bots/"+BotID+"/dynamicEntities/"+dynamicEntityId+"/pushRequests
URL url = new URL(targetUrl);
connection=(HttpURLConnection) url.openConnection();
connection.setUseCaches (false);
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
connection.setRequestProperty("Authorization", "Basic aWRjcy1vZGEtOTQxN2Y5MzU2MGI5NGViOGEyZTJhNGM5YWFjOWEzZmYtdDBfQVBQSUQ6MjQ0YWU4ZTItNmY3MS00YWYyLWI1Y2MtOTExMDg5MGQxNDU2");
connection.setRequestProperty("Accept", "application/json");
OutputStream os = connection.getOutputStream();
OutputStreamWriter osw = new OutputStreamWriter(os, "UTF-8");
**osw.write();** //this line is expecting input in parameter
osw.flush();
osw.close();
os.close();
connection.connect();
If I dont pass any value in osw.write() it gives compilation error. How can I resolve the same.

Look at the following method for the post call. You will need to add the outputstream to the osw.write() as it expects a parameter.
private static void sendPOST() throws IOException {
URL obj = new URL(POST_URL);
HttpURLConnection con = (HttpURLConnection) obj.openConnection();
con.setRequestMethod("POST");
con.setRequestProperty("User-Agent", USER_AGENT);
// For POST only - START
con.setDoOutput(true);
OutputStream os = con.getOutputStream();
os.write(POST_PARAMS.getBytes());
os.flush();
os.close();
// For POST only - END
int responseCode = con.getResponseCode();
System.out.println("POST Response Code :: " + responseCode);
if (responseCode == HttpURLConnection.HTTP_OK) { //success
BufferedReader in = new BufferedReader(new InputStreamReader(
con.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
response.append(inputLine);
}
in.close();
// print result
System.out.println(response.toString());
}
else {
System.out.println("POST request not worked");
}
}
For more details on the above code look here.

Sending a POST request to a server

I am trying to create my first android application that utilizes a REST api. My api is written in Node.JS and has already been tested using Postman, however, I am having trouble sending JSON data to my api.
#Override
protected String doInBackground(String... params) {
String data = "";
String urlName = params[0];
HttpURLConnection httpURLConnection = null;
try {
httpURLConnection = (HttpURLConnection) new URL(urlName).openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
DataOutputStream wr = new DataOutputStream(httpURLConnection.getOutputStream());
wr.writeBytes(params[1]);
wr.flush();
wr.close();
InputStream in = httpURLConnection.getInputStream();
InputStreamReader inputStreamReader = new InputStreamReader(in);
int inputStreamData = inputStreamReader.read();
while (inputStreamData != -1) {
char current = (char) inputStreamData;
inputStreamData = inputStreamReader.read();
data += current;
}
} catch (Exception e) {
e.printStackTrace();
} finally {
if (httpURLConnection != null) {
httpURLConnection.disconnect();
}
}
return data;
}
I always reach the line that declares and initializes my DataOutputSteam and doesn't execute the code. I am not even getting a log that my Virtual device has visited my server at all.
I have included in the manifest XML both of these already.
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.INTERNET" />

Based on your logs, you're hitting a NetworkOnMainThreadException and that's preventing the network request from being executed (it's going into your catch block instead). This suggests you aren't calling your AsyncTask correctly - ensure that you're calling execute instead of calling doInBackground. See also here for more information on this general pattern.

Try this, it is for POST method that accept 2 parameter email and password.
Change it based on your requirement
URL url = new URL(Login_url);
HttpURLConnection conn = (HttpURLConnection) new URL(urlName).openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Accept" , "application/json");
conn.connect();
Uri.Builder builder = new Uri.Builder()
.appendQueryParameter("email", "Your_Email")
.appendQueryParameter("password","Your_Password");
String query = builder.build().getEncodedQuery();
OutputStream os = conn.getOutputStream();
BufferedWriter writer = new BufferedWriter(
new OutputStreamWriter(os, "UTF-8"));
writer.write(query);
writer.flush();
writer.close();
os.close();
code = conn.getResponseCode();
Log.e("Result", code + "");
InputStream input = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(input));
StringBuilder result = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
Log.e("Result",result.toString());

HttpURLConnection update from Http Client

Hello I was wondering if somebody could help me with the following, I have a database that is currently populated. I used to call it using the http client and it worked fine but now I'm trying to update the code since its been deprecated to use the httpurlconnection but i have no success. I ve looked up some tutorials and tried a few thing but it doesn't seem to be working. the database is called through a php file and returns it in a json format.If i were to call the php file from my browser the response is the following: [{"id":"15","logo":"logo url","title":"title"}]
The error that I get on the console is the following:java.lang.NullPointerException: Attempt to invoke virtual method 'void java.io.InputStream.close()' on a null object reference
Which its not making much sense to me since the script pulls information
I have the following code, i left the commented section just in case i need any of it, It also includes the old way i used to call the DB Thank you!:
public void loadNews(){
InputStream is = null;
String result = "";
ArrayList<NameValuePair>();
try {
URL url = new URL("http://databasecall.php");
//HttpClient httpclient = new DefaultHttpClient();
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
//urlConnection.setRequestMethod("GET");
//urlConnection.setRequestProperty("Content-length", "0");
//urlConnection.setUseCaches(false);
//urlConnection.setAllowUserInteraction(false);
//urlConnection.setConnectTimeout(15000);
//urlConnection.setReadTimeout(15000);
//urlConnection.connect();
int responseCode = urlConnection.getResponseCode();
Log.i("Tag:", Integer.toString(responseCode)); //tag 200
//HttpPost httppost = new HttpPost("http://databasecall.php");
//httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
//HttpResponse response = httpclient.execute(httppost);
//HttpEntity entity = response.getEntity();
//is = entity.getContent();
/*}catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}*/
//convert response to string
//try{
//BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
if (responseCode == HttpURLConnection.HTTP_OK) {
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
//BufferedReader reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream(), "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result = sb.toString();
Log.i("Tag:", result);
}
}catch(Exception e){
Log.e("log_tag", "Error converting result " + e.toString());
}

Updated API
try {
String urlParameters = "name=toni&class=one&param3=ok";
byte[] postData = urlParameters.getBytes(Charset.forName("UTF-8"));
int postDataLength = postData.length;
String request = "http://rocks.php";
URL url = new URL(request);
HttpURLConnection cox = (HttpURLConnection) url.openConnection();
cox.setDoOutput(true);
cox.setDoInput(true);
cox.setInstanceFollowRedirects(false);
cox.setRequestMethod("POST");
cox.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
cox.setRequestProperty("charset", "utf-8");
cox.setRequestProperty("Content-Length",
Integer.toString(postDataLength));
cox.setUseCaches(false);
OutputStreamWriter writer = new OutputStreamWriter(
cox.getOutputStream());
writer.write(urlParameters);
writer.flush();
String line;
BufferedReader reader = new BufferedReader(new InputStreamReader(
cox.getInputStream()));
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
writer.close();
reader.close();
} catch (Exception e) {
result = e.toString();
Sucess = false;
e.printStackTrace();
}

How to add header to HttpRequest of GET method in Java

I have to pass a token as part of validation for each GET request to access RESTful web service. Below is the code I'm using it to access REST api:
public static String httpGet(String urlStr, String[] paramName, String[] paramVal) throws Exception {
URL url = new URL(urlStr);
HttpsURLConnection conn = (HttpsURLConnection) url.openConnection();
conn.setRequestMethod("GET");
conn.setDoOutput(true);
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
OutputStream out = conn.getOutputStream();
Writer writer = new OutputStreamWriter(out, "UTF-8");
for (int i = 0; i < paramName.length; i++) {
writer.write(paramName[i]);
writer.write("=");
writer.write(URLEncoder.encode(paramVal[i], "UTF-8"));
writer.write("&");
}
writer.close();
out.close();
if (conn.getResponseCode() != 200) {
System.out.println("Response code: "+conn.getResponseCode());
throw new IOException(conn.getResponseMessage());
}
BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream()));
StringBuilder sb = new StringBuilder();
String line;
while ((line = rd.readLine()) != null) {
sb.append(line);
}
rd.close();
conn.disconnect();
return sb.toString();
}
I can't see any such method to set Header conn.setHeader() provided for HttpsURLConnection. It should be something like X-Cookie: token={token}; please help me to find a way to set header.

You can use:
conn.addRequestProperty("X-Cookie", "token={token}");
or setRequestProperty() also works

You are already setting headers on your request in your code when you do the following:
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
I.e. if the service you are communicating with requires that you send your token in the "X-Cookie" header you can simply do the same for that header:
conn.setRequestProperty("X-Cookie", "token={token}");

Sending JSON request to hipchat

I am making something for my HipChat room but for it to work i have to send a JSON request of:
POST /v1/rooms/message?format=json&auth_token=token HTTP/1.1
Host: api.hipchat.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 138
room_id=10&from=Alerts&message=A+new+user+signed+up
So far i have this:
public static void send(String send){
URL url = null;
HttpURLConnection conn = null;
try{
url = new URL("http://api.hipchat.com");
conn = (HttpURLConnection)url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty("Content-Length", "138");
conn.setUseCaches (false);
conn.setDoInput(true);
conn.setDoOutput(true);
DataOutputStream wr = new DataOutputStream(
conn.getOutputStream ());
wr.writeBytes (send);
wr.flush ();
wr.close ();
InputStream is = conn.getInputStream();
BufferedReader rd = new BufferedReader(new InputStreamReader(is));
String line;
StringBuffer response = new StringBuffer();
while((line = rd.readLine()) != null) {
response.append(line);
response.append('\r');
}
rd.close();
System.out.println(line);
}catch(Exception e){
e.printStackTrace();
}finally{
if(conn != null) {
conn.disconnect();
}
}
}
But in the console it just returns null. How would i go about sending the above JSON request?
Thanks

Every time you loop here
while((line = rd.readLine()) != null) {
your line variable is replaced with the value returned by rd.readLine(). The last time it loops, that method call will return null. That's why line is null.
I'm going to assume you wanted to print out response.