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How to Close HttpsURLConnection Java

I am trying to request data from the server using HttpsURLConnection; I currently have the server requiring the user to enter a username and password via a prompt. In a web browser after you enter the correct username and password, the browser would save the username and password as a session cookie in your browser so you can visit other pages within site without being prompted for your credentials. But for the client which is in Java, it does not save the username and password. I am trying to use .disconnect() to close the connection, but I keep getting the following error:
java.lang.IllegalStateException: Already connected
at sun.net.www.protocol.http.HttpURLConnection.setRequestProperty(HttpURLConnection.java:3053)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.setRequestProperty(HttpsURLConnectionImpl.java:316)
My Java Code:
private static void sendPost(String _url) throws Exception {
String url = _url;
URL obj = new URL(url);
HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
con.setRequestMethod("POST");
int responseCode = con.getResponseCode();
Auth(con);
if (responseCode == 200) {
label.setText("Sucssesfully Scanned: " + StudID.getText());
} else {
label.setText("Error, please scan again");
}
con.disconnect();
}
private static ArrayList<String> Get(String _url) throws Exception {
ArrayList<String> list = new ArrayList<>();
JsonParser parser = new JsonParser();
String url = _url;
URL obj = new URL(url);
HttpsURLConnection con = (HttpsURLConnection) obj.openConnection();
Auth(con);
con.setRequestMethod("GET");
con.setRequestProperty("Accept", "application/json");
BufferedReader in = new BufferedReader(
new InputStreamReader(con.getInputStream()));
String inputLine;
StringBuffer response = new StringBuffer();
while ((inputLine = in.readLine()) != null) {
response.append(inputLine);
}
in.close();
con.disconnect();
JsonElement element = parser.parse(response.toString());
if (element.isJsonObject()) {
JsonObject data = element.getAsJsonObject();
for (int i = 0; i < data.get("chapels").getAsJsonArray().size(); i++) {
JsonObject jObj = (JsonObject) data.get("chapels").getAsJsonArray().get(i);
list.add(jObj.get("Name").toString().replaceAll("\"", "") + " - " + jObj.get("Loc").toString().replaceAll("\"", ""));
}
}
return (list);
}
private static void Auth(HttpsURLConnection con){
String encodedBytes = Base64.getEncoder().encodeToString((BCrypt.hashpw("swheeler17", BCrypt.gensalt(10)) + ":" + BCrypt.hashpw("Trinity", BCrypt.gensalt(10))).getBytes());
con.setRequestProperty("authorization", "Basic " + encodedBytes);
}
Example of username and password prompt: https://chapel-logs.herokuapp.com/chapel

java.lang.IllegalStateException: Already connected
That exception means that you have attempted to set the property giving the authorization for the request after it has been sent.
This is probably where it happens:
int responseCode = con.getResponseCode();
Auth(con);
and Auth calls setRequestProperty.
Asking for the response code causes the request to be sent if if hasn't already been sent. (Obviously ... you can't get the response code until you get the response, and the server can't give you one unless the request is sent.)
To answer your question, calling disconnect on the connection will disconnect the connection.
But that's not what is causing your problem. The stacktrace shows clearly that the exception is happening when something is calling setRequestProperty.

Based off of Stephen C's answer I determined the swap the order of:
int responseCode = con.getResponseCode();
Auth(con);
So the working solution is:
Auth(con);
int responseCode = con.getResponseCode();
I'm assuming ResponseCode() creates a request to the server if a request has not already been made, otherwise ResponseCode() uses the pre-existing request. Upon further testing, I concluded there is no need to call .disconnect().

Does Java URLConnection send Metadata?

when you open a connection via URLConnection to read the content of a Webpage,
try {
URL url = new URL("https://stackoverflow.com/questions/46939965/does-java-urlconnection-send-metadata");
URLConnection urlConnection = url.openConnection();
HttpURLConnection connection;
connection = (HttpURLConnection) urlConnection;
BufferedReader in = new BufferedReader(
new InputStreamReader(connection.getInputStream()));
String current;
while((current = in.readLine()) != null) {
urlString += current;
}
}catch(IOException e) {
e.printStackTrace();
}
what will Java leave for Information?
Will statistical data like the Webbrowser saved? Will that be the "Java"?
Thx for help,
~Corn

HTTP "metadata" is normally sent in the headers. The one that would indicate the web browser is typically called "USER_AGENT." I do not believe Java will populate these headers for you implicitly.

HttpURLConnection POST returning 400 Bad Request

I have tried every single question about it in here, but my code still returning 400, for every request that I try to do and I'm not getting what I'm doing wrong.
HttpURLConnection connection = null;
InputStream in = null;
try {
URL url = new URL(uri);
connection = (HttpURLConnection) url.openConnection();
connection.setReadTimeout(10000);
connection.setConnectTimeout(20000);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-type", "application/x-www-form-urlencoded");
connection.setDoInput(true);
connection.setDoOutput(true);
String query = "";
if (Validator.isNotNull(paramsMap) && !paramsMap.isEmpty()) {
Uri.Builder builder = new Uri.Builder();
for (Map.Entry<String, String> entry : paramsMap.entrySet()) {
builder.appendQueryParameter(entry.getKey(), entry.getValue());
}
query = builder.build().getEncodedQuery();
}
if (!query.isEmpty()) {
OutputStream os = connection.getOutputStream();
BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(os, "UTF-8"));
writer.write(query);
writer.flush();
writer.close();
os.close();
}
connection.connect();
int status = connection.getResponseCode();
if (status == 200) {
in = connection.getInputStream();
} else {
in = connection.getErrorStream();
}
} finally {
connection.disconnect();
}
return in;

I would try to get it working using a separate tool (there are quite a few browser plugins that let you create POST requests (Postman, HttpRequester, etc.) Use one of those to figure out exactly what you need to POST to get it to work. Once you have it working in one of the tools, you can do the same thing in your Java code.

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}");

URLConnection sometimes returns empty string response?

I'm making an http GET request. It works in about 70% of my attempts. For some reason, I sometimes get no response string from a successful connection. I just setup a button in my app which keeps firing the code below. One call might fail to reply with a string, the next call works fine:
private onButtonClick() {
try {
doit();
} catch (Exception ex) {
...
}
}
public void doit() throws Exception {
URL url = new URL("http://www.example.com/service");
HttpURLConnection connection = (HttpURLConnection)url.openConnection();
connection.setDoInput(true);
connection.setUseCaches(false);
connection.setAllowUserInteraction(false);
connection.setReadTimeout(30 * 1000);
connection.setRequestProperty("Connection", "Keep-Alive");
connection.setRequestProperty("Authorization",
"Basic " + Base64.encode("username" + ":" + "password"));
BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
String line = "";
StringBuilder sb = new StringBuilder();
while ((line = in.readLine()) != null) {
sb.append(line);
}
in.close();
connection.disconnect();
// Every so often this prints an empty string!
System.out.println(sb.toString());
}
am I doing something wrong here? It seems like maybe I'm not closing the connection properly from the last call somehow and the response gets mangled or something? I am also calling doit() from multiple threads simultaneously, but I thought the contents of the method are thread-safe, same behavior though,
Thanks
Thanks

That method looks fine. It's reentrant, so calls shouldn't interfere with each other. It's probably a server issue, either deliberate throttling or just a bug.
EDIT: You can check the status code with getResponseCode.

For checking ResponseCode:
BufferedReader responseStream;
if (((HttpURLConnection) connection).getResponseCode() == 200) {
responseStream = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
} else {
responseStream = new BufferedReader(new InputStreamReader(((HttpURLConnection) connection).getErrorStream(), "UTF-8"));
}
For empty content resposneCode is 204. So if u can get empty body just add one more "if" with 204 code.

We also came across with the similar scenario, I came across the following solution for this issue:
- Setting up a user agent string on URLConnection object.
URLConnection conn = url.openConnection();
conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 4.01; Windows NT)");
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