How to properly close HttpURLConnection on Android

Question

I'm using HttpURLConnection for querying back-end server. Requests are POST. My code looks like:

InputStream is = null;
HttpURLConnection connection = null;
try {
    connection = (HttpURLConnection)new URL(uri).openConnection();
    connection.setRequestMethod("POST");
    connection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded; charset=" + ENCODING);
    connection.setDoOutput(true);
    byte[] content = buildFormUrlEncoded(params);
    connection.setRequestProperty("Content-Length", String.valueOf(content.length));

    connection.connect();

    OutputStream os = null;
    try {
        os = connection.getOutputStream();
        os.write(content);
    } finally {
        if (os != null) { os.close(); }
    }

    is = connection.getInputStream();
    handle(is);
} finally {
    if (is != null) { is.close(); }
    if (connection != null) { connection.disconnect(); }
}

However I'm getting this StrictMode error:

A resource was acquired at attached stack trace but never released. See java.io.Closeable for information on avoiding resource leaks.
java.lang.Throwable: Explicit termination method 'close' not called
    at dalvik.system.CloseGuard.open(CloseGuard.java:184)
    at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.startHandshake(OpenSSLSocketImpl.java:300)
    at org.apache.harmony.xnet.provider.jsse.OpenSSLSocketImpl.startHandshake(OpenSSLSocketImpl.java:257)
    at libcore.net.http.HttpConnection.setupSecureSocket(HttpConnection.java:210)
    at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.makeSslConnection(HttpsURLConnectionImpl.java:477)
    at libcore.net.http.HttpsURLConnectionImpl$HttpsEngine.connect(HttpsURLConnectionImpl.java:432)
    at libcore.net.http.HttpEngine.sendSocketRequest(HttpEngine.java:282)
    at libcore.net.http.HttpEngine.sendRequest(HttpEngine.java:232)
    at libcore.net.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:80)
    at libcore.net.http.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:164)

When I am debugging code, os.close(), is.close() and connection.disconnect() is called.

Could StrictMode happen because of connection is keep alive in pool?

EDIT

• If connection.setRequestProperty("connection", "close"); is added the StrictMode error disappear.
• If http URL instead of https URL is used the StrictMode error disappear.
• If BufferedReader is used the StrictMode error happens less often.

I would like to keep https for security and keep alive to reduce handshake overhead.

EDIT 2

Looks like this occurs only in case of android 3.X and 4.0.X.

Answer 1

My code looks like this:

@Override
    protected Boolean doInBackground(Void... params) {
        JSONObject holder = new JSONObject();
        try {
            Resources res = getResources();

            holder.put(res.getString(R.string.str),"");


            URL url = new URL(res.getString(R.string.url));
            String charset = res.getString(R.string.utf);
            HttpURLConnection http = null;

                HttpsURLConnection https = (HttpsURLConnection) url.openConnection();

                http = https;
                http.setRequestMethod(res.getString(R.string.post));
                http.setDoInput(true);
                http.setDoOutput(true);
                http.setRequestProperty(res.getString(R.string.charset), charset);
                http.setRequestProperty(res.getString(R.string.content_type), "application/x-www-form-urlencoded;charset=" + charset);

                String query = String.format("query1=%s&query2=%s&query3=%s&query4=%s", 
                     URLEncoder.encode(res.getString(R.string.qu1), charset), 
                     URLEncoder.encode(res.getString(R.string.qu2), charset),
                     URLEncoder.encode(res.getString(R.string.qu3), charset),
                     URLEncoder.encode(holder.toString(), charset));

                OutputStream output = null;
                try {
                     output = http.getOutputStream();
                     output.write(query.getBytes(charset));
                } finally {
                     if (output != null) try { output.close(); } catch (IOException logOrIgnore) {}
                }
                //InputStream response = http.getInputStream();

                BufferedReader in = new BufferedReader(new InputStreamReader(http.getInputStream()),4800); 
                StringBuffer responseBuffer = new StringBuffer();
                String line;

                while ((line = in.readLine()) != null) { 
                    responseBuffer.append(line);
                }

                in.close();
                answer = new Gson().fromJson(responseBuffer.toString(), Answer.class);
                //s = responseBuffer.toString();
        } catch (Exception e) {
            e.printStackTrace();
            getData();
        }
        return true;
    }

I believe you'll find the answer there.

Answer 2

Try the following ,

After closing streams and connections make then null.

is=null;os=null;connection=null;