I have a very simple method to get InputStream from url:
private InputStream request(String uri) {
Log.d(TAG, "initialize request: "+uri);
try {
URL url = new URL(uri));
Log.d(TAG, "initialize req: "+url);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
Log.d(TAG, "initialize open conn");
if (connection.getResponseCode() == HttpURLConnection.HTTP_OK) {
Log.d(TAG, "initialize return is");
return connection.getInputStream();
} else {
Log.d(TAG, "initialize: fail");
}
} catch (Exception e) {
e.printStackTrace();
}
Log.d(TAG, "initialize: what happened?");
return null;
}
and it used to work perfect. But now, when I'm trying to use it, for some reason it stops on 'connection.getResponseCode()'. Just stops, nothing else happens. The logs looks like this:
tag: initialize req: http://uri.provided.to.method
tag: initialize open conn
And that's it. It literally stops there and doesn't print or return anything else. Same effect for 'connection.getResponseMessage()'. Any ideas why it happens and how to fix it?
Ok, problem solved. Apparently connection was made too early, before the url was ready.
Related
I have a POST message I absolutely have to send on Android in a given circumstance, to the point I would like it to keep trying until it completes. I was under the understanding that setting:
urlConnection.setConnectTimeout(0);
would keep trying the connection until it goes through, but what is actually happening is the try block is failing, and the UnknownHostException is being thrown instead:
private class SendAlert extends AsyncTask<String, String, String> {
protected String doInBackground(String... strings) {
Log.d(TAG, "sendAlarm: sending alarm");
String stringUrl = createUri();
HttpsURLConnection urlConnection = null;
BufferedReader reader = null;
String postData = "";
Log.d(TAG, "sendAlarm: apikey: " + apiKey);
try{
Log.d(TAG, "sendAlarm: trying");
URL finalURL = new URL(stringUrl);
urlConnection = (HttpsURLConnection)finalURL.openConnection();
urlConnection.setReadTimeout(10000);
urlConnection.setConnectTimeout(0);
urlConnection.setRequestProperty("Content-Type", "application/json;charset=UTF-8");
urlConnection.setRequestProperty("Accept","application/json");
urlConnection.setRequestProperty("x-api-key",apiKey);
urlConnection.setRequestMethod("POST");
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);
int responseCode = urlConnection.getResponseCode();
Log.d(TAG, "doInBackground: response code = " + responseCode);
}catch (MalformedURLException e) {
e.printStackTrace();
Log.d(TAG, "doInBackground: error 1 " + e.toString());
}catch(UnknownHostException e){
Log.d(TAG, "doInBackground: e: " + e);
Log.d(TAG, "doInBackground: retrying");
}
catch(Exception e){
Log.d(TAG, "doInBackground: error 2 " + e.toString());
}
Wondering what the best way to set up the post message on Android is, to keep trying the connection until it goes through, even if the phone is on airplane mode for 5 hours.
Edit: going of #user3252344's answer below, is there any problem with calling the function again directly in the catch block of the AyncTask:
catch(UnknownHostException e){
Log.d(TAG, "doInBackground: e: " + e);
Log.d(TAG, "doInBackground: retrying");
SendAlarm sendAlarm = new SendAlarm;
sendAlarm.execute();
}
Setting the connection timeout to 0 will mean it won't timeout, but if it fails to connect it won't handle it still. I'm guessing you get a an UnknownHostException because it fails to resolve the url since it can't reach a DNS server.
I'd suggest you just set a reasonable connection timeout, catch the timeout exception if it happens and re-run.
final int READ_TIMEOUT = 500; // Timeout
final int RETRY_MS = 2000; //Retry every 2 seconds
final Handler handler = new Handler();
Runnable myUrlCall = () -> {
try {
//Make things
urlConnect.setReadTimeout(READ_TIMEOUT);
//Make the URL call, do response
} catch (SocketTimeoutException e) {
handler.postDelayed(myUrlCall, RETRY_MS);
} catch (/* other unintended errors*/ e) {
//Log the error or alert the user
}
};
handler.post(myUrlCall);
Possible even better idea: use Android settings to check if there's internet before you make the call. If there's no internet, use a longer delay. Something like this would be the code you're looking for.
I'm trying to connect to a web API using a URL. However, I get a 301 error from the server (Moved Permanently), although the provided URL works very well with no errors when I try it in my browser.
Here is the code that builds the URL:
public Loader<List<Earthquake>> onCreateLoader(int i, Bundle bundle) {
SharedPreferences sharedPrefs = PreferenceManager.getDefaultSharedPreferences(this);
String minMagnitude = sharedPrefs.getString(
getString(R.string.settings_min_magnitude_key),
getString(R.string.settings_min_magnitude_default));
String orderBy = sharedPrefs.getString(
getString(R.string.settings_order_by_key),
getString(R.string.settings_order_by_default)
);
Uri baseUri = Uri.parse(USGS_REQUEST_URL);
Uri.Builder uriBuilder = baseUri.buildUpon();
uriBuilder.appendQueryParameter("format", "geojson");
uriBuilder.appendQueryParameter("limit", "10");
uriBuilder.appendQueryParameter("minmag", minMagnitude);
uriBuilder.appendQueryParameter("orderby", orderBy);
Log.i ("the uri is ", uriBuilder.toString());
return new EarthquakeLoader(this, uriBuilder.toString());
}
Here is the code that tries to connect to the resource represented by the URL:
private static String makeHttpRequest(URL url) throws IOException {
String jsonResponse = "";
// If the URL is null, then return early.
if (url == null) {
return jsonResponse;
}
Log.i("The received url is " , url +"");
HttpURLConnection urlConnection = null;
InputStream inputStream = null;
try {
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setReadTimeout(10000 /* milliseconds */);
urlConnection.setConnectTimeout(15000 /* milliseconds */);
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// If the request was successful (response code 200),
// then read the input stream and parse the response.
if (urlConnection.getResponseCode() == 200) {
inputStream = urlConnection.getInputStream();
jsonResponse = readFromStream(inputStream);
} else {
Log.e(LOG_TAG, "Error response code: " + urlConnection.getResponseCode()); //this log returns 301
}
} catch (IOException e) {
Log.e(LOG_TAG, "Problem retrieving the earthquake JSON results.", e);
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
if (inputStream != null) {
// Closing the input stream could throw an IOException, which is why
// the makeHttpRequest(URL url) method signature specifies than an IOException
// could be thrown.
inputStream.close();
}
}
return jsonResponse;
}
I could know that the connection returns status code of 301 from the log provided in the case when the status code is not 200. I have also logged the generated URL, I copied it from the logcat and tried it in my browser and it worked well. Here is the built URL: http://earthquake.usgs.gov/fdsnws/event/1/query?format=geojson&limit=10&minmag=6&orderby=magnitude
I checked this question: Android HttpURLConnection receives HTTP 301 response code but it wasn't clear to me what is the solution for the problem.
Can you please help me identify and solve the problem?
UPDATE: As greenapps indicated in his comment, the connection is done through https. That comment identified the problem and helped me fix the code.
In my code, the string I used to build the basic URL, had the protocol value as http not https, it was:
private static final String USGS_REQUEST_URL =
"http://earthquake.usgs.gov/fdsnws/event/1/query";
After reading greenapps comment, I just changed the protocol part in the string to https, so it became:
private static final String USGS_REQUEST_URL =
"https://earthquake.usgs.gov/fdsnws/event/1/query";
That solved the problem.
Thanks.
If you click your http link here you will see that the browser shows a https page. You better use that url directly as there is redirection now.
This is because the address http to https transferred.
To avoid this, you need to convert the request address to https.
I'm writing a program that connects to a servlet thanks to a HttpURLConnection but I stuck while checking the url
public void connect (String method) throws Exception {
server = (HttpURLConnection) url.openConnection ();
server.setDoInput (true);
server.setDoOutput (true);
server.setUseCaches (false);
server.setRequestMethod (method);
server.setRequestProperty ("Content-Type", "application / xml");
server.connect ();
/*if (server.getResponseCode () == 200)
{
System.out.println ("Connection OK at the url:" + url);
System.out.println ("------------------------------------------- ------- ");
}
else
System.out.println ("Connection failed");
}*/
I got the error :
java.net.ProtocolException: Cannot write output after reading input.
if i check the url with the code in comments but it work perfectly without it
unfortunately, I need to check the url so i think the problem comes from the getResponseCode method but i don t know how to resolve it
Thank you very much
The HTTP protocol is based on a request-response pattern: you send your request first and the server responds. Once the server responded, you can't send any more content, it wouldn't make sense. (How could the server give you a response code before it knows what is it you're trying to send?)
So when you call server.getResponseCode(), you effectively tell the server that your request has finished and it can process it. If you want to send more data, you have to start a new request.
Looking at your code you want to check whether the connection itself was successful, but there's no need for that: if the connection isn't successful, an Exception is thrown by server.connect(). But the outcome of a connection attempt isn't the same as the HTTP response code, which always comes after the server processed all your input.
I think the exception is not due toprinting url. There should some piece of code which is trying to write to set the request body after the response is read.
This exception will occur if you are trying to get HttpURLConnection.getOutputStream() after obtaining HttpURLConnection.getInputStream()
Here is the implentation of sun.net.www.protocol.http.HttpURLConnection.getOutputStream:
public synchronized OutputStream getOutputStream() throws IOException {
try {
if (!doOutput) {
throw new ProtocolException("cannot write to a URLConnection"
+ " if doOutput=false - call setDoOutput(true)");
}
if (method.equals("GET")) {
method = "POST"; // Backward compatibility
}
if (!"POST".equals(method) && !"PUT".equals(method) &&
"http".equals(url.getProtocol())) {
throw new ProtocolException("HTTP method " + method +
" doesn't support output");
}
// if there's already an input stream open, throw an exception
if (inputStream != null) {
throw new ProtocolException("Cannot write output after reading
input.");
}
if (!checkReuseConnection())
connect();
/* REMIND: This exists to fix the HttpsURLConnection subclass.
* Hotjava needs to run on JDK.FCS. Do proper fix in subclass
* for . and remove this.
*/
if (streaming() && strOutputStream == null) {
writeRequests();
}
ps = (PrintStream)http.getOutputStream();
if (streaming()) {
if (strOutputStream == null) {
if (fixedContentLength != -) {
strOutputStream =
new StreamingOutputStream (ps, fixedContentLength);
} else if (chunkLength != -) {
strOutputStream = new StreamingOutputStream(
new ChunkedOutputStream (ps, chunkLength), -);
}
}
return strOutputStream;
} else {
if (poster == null) {
poster = new PosterOutputStream();
}
return poster;
}
} catch (RuntimeException e) {
disconnectInternal();
throw e;
} catch (IOException e) {
disconnectInternal();
throw e;
}
}
I have this problem too, what surprises me is that the error is caused by my added code System.out.println(conn.getHeaderFields());
Below is my code:
HttpURLConnection conn=(HttpURLConnection)url.openConnection();
conn.setRequestMethod("POST");
configureConnection(conn);
//System.out.println(conn.getHeaderFields()); //if i comment this code,everything is ok, if not the 'Cannot write output after reading input' error happens
conn.connect();
OutputStream os = conn.getOutputStream();
os.write(paramsContent.getBytes());
os.flush();
os.close();
I had the same problem.
The solution for the problem is that you need to use the sequence
openConnection -> getOutputStream -> write -> getInputStream -> read
That means..:
public String sendReceive(String url, String toSend) {
URL url = new URL(url);
URLConnection conn = url.openConnection();
connection.setDoInput(true);
connection.setDoOutput(true);
connection.sets...
OutputStreamWriter out = new OutputStreamWriter(conn.getOutputStream());
out.write(toSend);
out.close();
BufferedReader in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
String receive = "";
do {
String line = in.readLine();
if (line == null)
break;
receive += line;
} while (true);
in.close();
return receive;
}
String results1 = sendReceive("site.com/update.php", params1);
String results2 = sendReceive("site.com/update.php", params2);
...
I would like to make a simple HTTP HEAD request, without keep-alive.
How can I do that in Android?
using HttpClient:
As njzk2 suggested, with HttpClient() it's very straightforward:
HttpResponse response = new HttpClient().execute(new HttpHead(myUrl));
However there is a problem with not being able to close the connection. Usually on the HttpClient, you would get the entity using:
HttpEntity entity = response.getEntity();
and then you would get the input stream from the entity
InputStream instream = entity.getContent();
...
instream.close();
and by closing the input stream, the connection would close.
However, in the case of a HEAD request, the entity appears to be null (possibly because HEAD requests don't return the body in the response), so the input stream cannot be fetched and closed and the connection doesn't close either.
In the last edit to his answer, njzk2 is suggesting to use AndroidHttpClient, which is a more recent implementation (API 8) of HttpClient and it actually has a close() method. I haven't used it but I guess it will work fine. However, as the Android development team suggests, the HttpUrlConnection should be the preferred Android client to use.
using HttpUrlConnection:
Actually it seems quite easy to make HEAD requests using HttpUrlConnection and make sure that the connection closes:
HttpURLConnection urlConnection = null;
System.setProperty("http.keepAlive", "false");
try {
URL url = new URL(stringUrl);
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("HEAD");
urlConnection.getInputStream().close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (urlConnection != null) {
urlConnection.disconnect();
}
}
Trivially :
HttpResponse response = new AndroidHttpClient().execute(new HttpHead(myUrl));
Typically you'll use the same AndroidHttpClient for several connections, then call close on it.
For ordinary Java and Android
I am using some standard Java code to test the existence of a resource and in the same time to check whether a resource has been changed, provided the parameter if_modified_since is non-zero.
URL url = new URL(adr);
try {
URLConnection con = url.openConnection();
con.setIfModifiedSince(if_modified_since);
if (con instanceof HttpURLConnection) {
/* Workaround for https://code.google.com/p/android/issues/detail?id=61013 */
con.addRequestProperty("Accept-Encoding", "identity");
((HttpURLConnection) con).setRequestMethod("HEAD");
int response = ((HttpURLConnection) con).getResponseCode();
if (response == HttpURLConnection.HTTP_UNAVAILABLE)
return false;
if (response == HttpURLConnection.HTTP_NOT_MODIFIED)
return false;
}
if (if_modified_since != 0) {
long modified = OpenOpts.getLastModified(con);
if (modified != 0 && if_modified_since >= modified)
return false;
}
InputStream in = con.getInputStream();
in.close();
return true;
} catch (FileNotFoundException x) {
return false;
} catch (UnknownHostException x) {
return false;
} catch (SocketException x) {
return false;
}
Interestingly the code needs a con.getInputStream() and I don't get some errors here. But I needed some helper code, to also cater for URIs that point to JARs. The helper code is:
private static long getLastModified(URLConnection con)
throws IOException {
if (con instanceof JarURLConnection) {
return ((JarURLConnection) con).getJarEntry().getTime();
} else {
return con.getLastModified();
}
}
The code can be further optimized by some specialization if the
URI is schema file: , one can then directly do File.exists() and File.getLastModified().
We do not throw a ServiceUnvailable exception here, we basically assume that the outer code would catch an IOException and then assume a false
result of the getHead().
I am working on an application that uses HttpUrlConnection, connects beautifully with the server, but when fetching data from it says connection time out IOException.
The internet, & network permissions are already set in the android.manifest; there are no bars showing up in the android emulator (does this says anything).
Read at developer.android.com:
The functional limitations of the emulator include:
- No support for determining network connected state
- and few others....
Any help will be highly appreciated. And I don't have an actual device to test this.
Received server info do gets printed in the logcat.
Thanks...
Here is the code:
URL url = new URL(urlString);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
try {
Log.i(INFO_TAG, "Received server:" + conn.toString());
conn.setInstanceFollowRedirects(true);
conn.setRequestMethod("GET");
conn.setRequestProperty("Content-length", "0");
conn.setUseCaches(false);
conn.setAllowUserInteraction(false);
conn.setConnectTimeout(25000 /* milliseconds */);
conn.setReadTimeout(15000/* 10000 *//* milliseconds */);
// conn.setDoInput(true);
// Starts the query
conn.connect();
status = conn.getResponseCode();
Log.d(DEBUG_TAG, "Status recevied is: " + conn.getResponseCode());
responseCode = status;
if (responseCode == 200) {
Log.i(INFO_TAG, "URL Connection OK");
contentIs = conn.getInputStream();
BufferedReader reader = new BufferedReader(
new InputStreamReader(contentIs));
String line;
while ((line = reader.readLine()) != null) {
builder.append(line);
Log.i(INFO_TAG, "Data Read is: " + line);
}
} else {
Log.d(DEBUG_TAG, "Could not read data from web server");
Log.e(ConnectAndGetData.class.toString(),
"Failed to download content");
}
}// end of try
catch (Exception ex) {
// This is currently being printout
Log.d(DEBUG_TAG, "Received an exception" + ex.toString(), ex);
ex.printStackTrace();
throw new IOException("Error Connecting" + ex.toString());// "Error connecting");
} finally {
if (contentIs != null) {
contentIs.close();
conn.disconnect();
}
}
One more thing since, it throws a connection timeout exception it does not debug info at this line is printed:
Log.d(DEBUG_TAG, "Status recevied is: " + conn.getResponseCode());
You need to write
conn.setDoInput( true ); after this line
conn.setConnectTimeout(25000 /* milliseconds */);
conn.setReadTimeout(15000/*10000*/ /* milliseconds */);
Its Sets the flag indicating whether this URLConnection allows input.
The emulator can't receive any response from server. I think the problem with your network connection. Check your proxy settings.
The problem was not the code above, it was the server code (the main culprit). Now implemented a web service and the code above is working fine.
Thanks all for commenting...