Develop Reference

How setConnectTimeout can work?

I read many posts about setConnectTimeout but I really wonder how this method could work because we cannot initialize it before openConnection() exists.
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setConnectTimeout(5000);
urlConnection.setReadTimeout(2000);
...
So what is the purpose of setConnectTimeout()?

You're just opening / initializing the connection. You haven't actually called urlConnection.connect() yet. You're only initializing things like the URL, headers, setting your request method, etc.
It'll come into effect once you actually run the connection.

HttpURLConnection getInputStream() returns empty for specific device

Im experiencing a strange behaviour when using HttpURLConnection getInputStream() on a different devices. On all devices except "Alcatel" im getting a valid input stream only for Alcatel devices im getting a different(empty) kind of input stream:
All devices except alcatel
Alcatel devices
Im making the exact same call and getting 200 for all the devices.
The code is pretty straightforward:
urlObj = new URL(url);
urlConnection = (HttpURLConnection)urlObj.openConnection();
urlConnection.setRequestMethod(method);
urlConnection.setDoInput(true);
urlConnection.setConnectTimeout(timeout);
urlConnection.setReadTimeout(timeout);
urlConnection.setDoOutput(true);
urlConnection.setFixedLengthStreamingMode(body.length);
urlConnection.setRequestProperty(HEADER_KEY_CONTENT_LENGTH, String.valueOf(body.length));
urlConnection.getOutputStream().write(body);
int responseCode = urlConnection.getResponseCode();
InputStream in = urlConnection.getInputStream();
Any suggestions?

Please check if you need to have proxy setting for alcatel. httpurlconnection may fail without proper proxy gateway.

setRequestProperty throwing java.lang.IllegalStateException: Cannot set request property after connection is made

I am getting java.lang.IllegalStateException:
java.lang.IllegalStateException: Cannot set request property after connection is made error when setRequestProperty method is called after
url.openConnection();
Here is what i am trying:
URL url = new URL("https://49.205.102.182:7070/obsplatform/api/v1/mediadevices/545b801ce37e69cc");
urlConnection = (HttpsURLConnection) url
.openConnection();
urlConnection.setRequestProperty("Content-Type","application/json");
any suggestions please? Thanks in advance.

This usually happens if you have in the debug watchers calls, such as conn.getResponseCode() or anything that queries the request result before the request was actually issued or completed.
This causes, that during debug, a request is performed by the watcher, before having properly set you request, and then it becomes invalid.

I only have this issue while in debugging mode,
Run without debugging (You can print logs) everything should work fine

The obvious thing is to think that you need to add properties before calling open on the URL. this however is not the case. i have seen many samples of settings being set AFTER url has been open (as counter intuitive as that is).
the problem in my case is that i had conn.getResponseCode() added in my watch list. removed that and all good.
... tricky.

please check below code
HttpURLConnection httpcon = (HttpURLConnection) ((new URL("a url").openConnection()));
httpcon.setDoOutput(true);
httpcon.setRequestProperty("Content-Type", "application/json");
httpcon.setRequestProperty("Accept", "application/json");
httpcon.setRequestMethod("POST");
httpcon.connect();

I was getting the same exception on setRequestProperty("Range","byte=" + downloadedSize + "-") .
After adding connection.setChunkedStreamingMode(0); the issue disappeared

I'm having the same issue.
I was observing this issue on Nexus 5. Code of my app constantly fails with the same exception (or its twin brother "cannot set request method ..")
What I've observed that it happens if i leave phone for a while. One it starts failing it fails all the time - but if i restart phone/emulator it's ok once again).
My suspicion is its either some bug in connection pooling on framework side, or somewhere in code resources are leaked.

i found the problem it's about ordering the code, if you are trying to add header and post parameters both, it's important to be careful about this
HttpURLConnection connection = (HttpURLConnection) urlConnection;
//// Add Request Headers
for (NameValuePair nvp :
request[0].getHeaderParams()) {
connection.setRequestProperty(nvp.getName(),nvp.getValue());
}
// done
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setRequestMethod("POST");
//// Add Post Parameters
OutputStream outputStream = urlConnection.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
List<NameValuePair> params = new ArrayList<>(request[0].getPostParams());
bufferedWriter.write(getQuery(params));
// done
connection.setConnectTimeout(3000);
connection.setReadTimeout(3000);
bufferedWriter.flush();
bufferedWriter.close();
outputStream.flush();
outputStream.close();
connection.connect();
in here, i have added header parameters then set setDoInput and setDoOutput then setRequestMethod and finally you can add POST parameters.
i don't know what is wrong with setRequestMethod but i think its preparing the connection by opening it or something and that's why it throws exception

not invoke setRequestProperty after write byte to OutputStream.
OutputStream os = connection.getOutputStream();
os.write("k=v".getBytes());
os.close();
you should invoke setRequestProperty above the code

To avoid the error:
java.lang.IllegalStateException: Cannot set request property after connection is made
We have to check the connection response before access the request header fields :
URL url = new URL("https://49.205.102.182:7070/obsplatform/api/v1/mediadevices/545b801ce37e69cc");
urlConnection = (HttpsURLConnection) url
.openConnection();
//Check connection
if(urlConnection.getResponseCode() == 200/*Successful*/) {
urlConnection.setRequestProperty("Content-Type","application/json");
...
...
}

FileNotFoundException for HttpURLConnection in Ice Cream Sandwich

I have an Android app that works fine with Android 2.x and 3.x, but it fails when run on Android 4.x.
The problem is in this section of code:
URL url = new URL("http://blahblah.blah/somedata.xml");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.setDoOutput(true);
urlConnection.connect();
InputStream inputStream = urlConnection.getInputStream();
When the application is running on Android 4.x, the getInputStream() call results in a FileNotFoundException. When the same binary is running on earlier versions of Android, it succeeds. The URLs also work fine in web browsers and with curl.
Apparently something about HttpURLConnection has changed in ICS. Does anybody have any idea what has changed, and/or what the fix might be?

Try removing the setDoOutput call. Taken from this blog:
a blog
Edit: This is needed when using a POST call.

A FileNotFoundException may also been thrown if the server returns a bad error code (e.g., 400 or 401). You can handle this as follows:
int responseCode = con.getResponseCode(); //can call this instead of con.connect()
if (responseCode >= 400 && responseCode <= 499) {
throw new Exception("Bad authentication status: " + responseCode); //provide a more meaningful exception message
}
else {
InputStream in = con.getInputStream();
//etc...
}

I Don't know why, but dealing manually with redirection resolves the problem.
connection.setInstanceFollowRedirects(false);

A little late but you can also verify the accepted content. You can add this line to accept all kinds of contents
urlConnection.setRequestProperty("Accept","*/*");

Android POST Message Doesn't get Sent

I've encountered a rather strange error. I've written an android application that uploads an simple text file to a server. The code for the connection is as follows:
try {
URL = new URL(myURL);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setDoInput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-Type", "multipart/form-data; boundary="+"---");
DataOutputStream output = new DataOutPutstream(connection.getOutputStream());
output.writeBytes(<my post request>);
output.flush();
output.close();
connection.connect();
}
When I run this method, the post request is never sent over to the server. Nothing shows up on wireshark and if I look in logcat, there are no errors and the connection gets made fine, the POST message is just never sent. However, if I add a simple line right after the connection.connect() such as:
connection.getResponseCode();
Suddenly the POST message gets sent over no problem. What's going on here? Am I required to get a response code in order for the message to get sent over?

Why do you have to call URLConnection#getInputStream to be able to write out to URLConnection#getOutputStream?
In short you must call getInputStream() and close it. getResponseCode() is also working because it requires an established connection.
You do not need to call
connection.connect();
which is redundant.
You can get working sample from here: http://www.xyzws.com/Javafaq/how-to-use-httpurlconnection-post-data-to-web-server/139

You set doInput to true. Maybe the url connection waits for an input because of that. Try to set it to false. But I could also be wrong. It is just a guess.