com.lillicoder.newsblurry.feeds.FeedRepository.java Source code

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Here is the source code for com.lillicoder.newsblurry.feeds.FeedRepository.java

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/**
 * Copyright 2012 Scott Weeden-Moody
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.lillicoder.newsblurry.feeds;

import java.util.HashMap;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONException;

import android.annotation.SuppressLint;
import android.content.Context;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.util.Log;

import com.lillicoder.newsblurry.R;

/**
 * Repository that stores and manages {@link Feed} in persistent storage.
 * @author lillicoder
 */
@SuppressLint("UseSparseArrays")
public class FeedRepository {

    private static final String TAG = FeedRepository.class.getSimpleName();

    private static final String EXCEPTION_INVALID_CONSTRUCTOR_CONTEXT = "The given context must not be null.";

    private static final String WARNING_FAILED_TO_RESTORE_FEEDS_JSON = "Failed to restore feeds JSON from JSON string, will not load feeds into memory.";

    private static final String WARNING_FAILED_TO_SAVE_FEED_TO_JSON = "Failed to write feed %d to feeds JSON, feed will not be saved.";

    private Context _context;

    public FeedRepository(Context context) {
        if (context == null)
            throw new IllegalArgumentException(EXCEPTION_INVALID_CONSTRUCTOR_CONTEXT);

        this.setContext(context);
    }

    /**
     * Gets the application default {@link SharedPreferences}.
     * @return Application default {@link SharedPreferences}.
     */
    private SharedPreferences getSharedPreferences() {
        Context context = this.getContext();

        String appPreferencesName = context.getString(R.string.default_preferencesName);
        return context.getSharedPreferences(appPreferencesName, Context.MODE_PRIVATE);
    }

    /**
     * Gets the {@link Context} for this repository.
     * @return {@link Context} for this repository.
     */
    private Context getContext() {
        return this._context;
    }

    /**
     * Sets the {@link Context} for this repository.
     * @param context {@link Context} for this repository.
     */
    private void setContext(Context context) {
        this._context = context;
    }

    /**
     * Restores feeds saved in storage and returns
     * a map of the restored feeds keyed by feed ID. 
     * @return {@link Map} of restored {@link Feed} keyed by feed ID.
     */
    public Map<Integer, Feed> restoreFeeds() {
        Map<Integer, Feed> feedsById = new HashMap<Integer, Feed>();

        Context context = this.getContext();
        SharedPreferences preferences = this.getSharedPreferences();

        String feedsJsonText = preferences.getString(context.getString(R.string.preference_persistedFeeds), null);
        if (feedsJsonText != null) {
            try {
                JSONArray feedsArrayJson = new JSONArray(feedsJsonText);
                FeedParser parser = new FeedParser(context);
                feedsById = parser.parseFeedsById(feedsArrayJson);
            } catch (JSONException e) {
                Log.w(TAG, WARNING_FAILED_TO_RESTORE_FEEDS_JSON, e);
            }
        }

        return feedsById;
    }

    /**
     * Saves the given map of feeds to storage.
     */
    public void saveFeeds(Map<Integer, Feed> feedsById) {
        // Create a feeds JSON object we can write to storage.
        JSONArray feedsJson = new JSONArray();
        for (Feed feed : feedsById.values()) {
            try {
                feedsJson.put(feed.toJson());
            } catch (JSONException e) {
                Log.w(TAG, String.format(WARNING_FAILED_TO_SAVE_FEED_TO_JSON, feed.getId()), e);
            }
        }

        // Write data to storage.
        Context context = this.getContext();
        SharedPreferences preferences = this.getSharedPreferences();
        Editor editor = preferences.edit();

        editor.putString(context.getString(R.string.preference_persistedFeeds), feedsJson.toString());
        editor.commit();
    }

}