RemoteService.java

/*******************************************************************************
 * Copyright (c) 2011 Michel DAVID mimah35-at-gmail.com
 * 
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * 
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 ******************************************************************************/
package fr.gotorennes.remote;

import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URLEncoder;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import org.json.JSONTokener;

import android.util.Log;

public abstract class RemoteService<T> {

	private static final String TAG = "GoToRennes.RemoteService";

	private static final String apiUrl = "http://data.explore.star.fr/api/records/1.0/search/?apikey=050bf390daf3dcd58962faa939c0572552b200bb4fab710fdb3c56bf&dataset=";

	private static HttpClient httpclient = new DefaultHttpClient();

	protected abstract T populate(JSONObject jsonObject) throws JSONException;
	
	protected abstract String getDataSet();
	
	protected T loadObject(String query) {
		List<T> list = loadList(query);
		return list.isEmpty() ? null : list.get(0);
	}
	
	protected List<T> loadList() {
		return loadList(null);
	}
	
	protected List<T> loadList(String query) {
		return loadList(query, null, 1000);
	}
	
	protected List<T> loadProximityList(double latitude, double longitude, int count) {
		return loadList(null, String.valueOf(latitude) + "," + String.valueOf(longitude) + "," + 5000, count);
	}

	protected List<T> loadList(String query, String geofilter, int count) {
		List<T> result = new ArrayList<T>();
		JSONArray data = getData(query, geofilter, count);
		if (data != null) {
			try {
				for (int i = 0; i < data.length(); i++) {
					JSONObject jsonObject = data.getJSONObject(i);
					onDataLoad(jsonObject);
					result.add(populate(jsonObject.getJSONObject("fields")));
				}
			} catch (Exception e) {
				Log.e(TAG, "Echec de lecture de la réponse du service distant : " + e.getMessage());
			}
		}
		return result;
	}

	protected void onDataLoad(JSONObject data) throws JSONException {
		// Nothing
	}

	protected JSONArray getData(String query, String geofilter, int count) {
		String url = apiUrl + getDataSet();
		if (query != null) {
			url += "&" + query;
		}
		if (geofilter != null) {
			url += "&geofilter.distance=" + encode(geofilter);
		}
		url += "&rows=" + count;
		
		//Log.d("GoToRennes", url);
		HttpEntity entity = getEntity(url);
		
		if (entity == null) {
			return null;
		}

		String json = readFully(entity);
		if (json == null) {
			return null;
		}

		try {
			JSONObject object = (JSONObject) new JSONTokener(json).nextValue();
			return object.optJSONArray("records");
		} 
		catch (Exception e) {
			Log.e(TAG, "Echec de lecture de la réponse du service distant : " + e.getMessage());
		}
		return null;
	}
	
	public static String encode(String query) {
		try {
			return URLEncoder.encode(query, "UTF-8");
		}
		catch(Exception ex) {
			return query;
		}
	}

	public static HttpEntity getEntity(String url) {
		HttpGet httpget = new HttpGet(url);
		try {
			HttpResponse response = httpclient.execute(httpget);
			if (response != null) {
				return response.getEntity();
			}
		} catch (Exception e) {
			Log.e(TAG, "Echec d'accès au service distant : " + e.getMessage());
		}
		return null;
	}
	
	public static String readFully(String url) {
		HttpEntity entity = getEntity(url);
		if (entity == null) {
			return null;
		}
		return readFully(entity);
	}

	public static String readFully(HttpEntity entity) {
		InputStream instream = null;
		try {
			instream = entity.getContent();
			BufferedReader reader = new BufferedReader(new InputStreamReader(instream));

			StringBuilder json = new StringBuilder();
			String line = null;
			while ((line = reader.readLine()) != null) {
				json.append(line);
			}
			return json.toString();
		} catch (Exception e) {
			Log.e(TAG, "Echec de lecture de la réponse du service distant : " + e.getMessage());
		} finally {
			if (instream != null) {
				try {
					instream.close();
				} catch (Exception e) {
					Log.e(TAG, "Echec de fermeture du flux du service distant : " + e.getMessage());
				}
			}
		}
		return null;
	}
}