Android Open Source - streaming_project Data Fetcher

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License

The source code is released under:

GNU General Public License

Java Source Code

package com.example.streaming.streaming;
// w  ww .  j  av  a 2 s.c  om

import android.content.Context;
import android.net.Uri;
import android.util.Log;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Properties;


// Handles the networking in the Streaming application
// NOTE 1: networking permission is added to manifest
// NOTE 2: getURL() cannot be directly called from an Activity. The networking code must be
// run from a background thread (created by AsyncTask) because Android has disallowed network
// operations on the main thread starting with Honeycomb
public class DataFetcher {
    // For debugging
    public static final String TAG = "Fetcher";
    private String mUriString;
    private Context mContext;
    private Properties mProperties;


    public DataFetcher(Context context) {
        mContext = context;
        AssetsPropertyReader propertiesReader = new AssetsPropertyReader(mContext);
        mProperties = propertiesReader.getProperties("app.properties");
        mUriString = mProperties.getProperty("server_url");
    }

    // Fetches raw data from a URL and returns it as an array of bytes
    byte[] getUrlBytes(String urlSpec) throws IOException {
        // Create a URL object from a string (e.g.. http://www.google.com)
        URL url = new URL(urlSpec);
        // openConnection() creates a connection object pointed at the URL
        // NOTE 1: Cast the the URLConnection object (as returned by openConnection()) to
        // HttpsURLConnection since we are connection to an https URL
        // This gives us HTTP-specific interfaces for working with request methods, response codes,
        // streaming methods, and more
        // NOTE 2: HttpsURLConnection represents a connection, but it will not actually connect to
        // the endpoint until getInputStream() is called (or getOutputStream() for POST calls).
        // Until then, you cannot get a valid response code.
        HttpURLConnection connection = (HttpURLConnection)url.openConnection();
        // TODO: add this timeout in the properties file
        connection.setConnectTimeout(10000);
        // Once the URL object is created and the connection is opened, we can read the incoming data
        try {
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            // InputStream returns bytes as they are available
            InputStream in = connection.getInputStream();

            if (connection.getResponseCode() != HttpURLConnection.HTTP_OK) {
                String message = "Response code is " + connection.getResponseCode();
                Log.e(TAG, message);
                throw new IOException(message);
            }

            int bytesRead;
            byte[] buffer = new byte[1024];
            while ((bytesRead = in.read(buffer)) > 0) {
                out.write(buffer, 0, bytesRead);
            }
            out.close();
            return out.toByteArray();
        } catch (IOException e) {
            Log.e(TAG, e.getMessage());
            throw new IOException(e.getMessage());
        } finally {
            connection.disconnect();
        }
    }

    // Converts the bytes fetched by getUrlBytes() into a String
    public String getUrl(String urlSpec) throws IOException {
        byte[] result = getUrlBytes(urlSpec);
        return new String(result);
    }

    // Builds an appropriate API request URL and fetches its contents as a String
    public String fetchData(String query) throws IOException {
        String str;

        // Build the complete URL for the getListFiles request
        // NOTE 1: Uri.Builder is a convenience class for creating properly escaped parameterized
        // URLs.
        // NOTE 2: appendQueryParameter() automatically escapes query strings
        String url = Uri.parse(mUriString).buildUpon()
                .appendPath(query)
                .build().toString();

        str = getUrl(url);
        Log.i(TAG, "Received data");

        return str;
    }
}

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