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/* * Adapted from Android SDK to support custom file names and logging * ----------------------------------------------------------------- *// www . ja v a2s .c o m * Copyright (C) 2007 The Android Open Source Project * * 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.github.dkharrat.nexusdata.utils.android; import java.io.File; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import android.content.Context; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteDatabase.CursorFactory; import android.database.sqlite.SQLiteException; /** * A helper class to manage database creation and version management. * * <p>You create a subclass implementing {@link #onCreate}, {@link #onUpgrade} and * optionally {@link #onOpen}, and this class takes care of opening the database * if it exists, creating it if it does not, and upgrading it as necessary. * Transactions are used to make sure the database is always in a sensible state. * * <p>This class makes it easy for {@link android.content.ContentProvider} * implementations to defer opening and upgrading the database until first use, * to avoid blocking application startup with long-running database upgrades. * * <p>For an example, see the NotePadProvider class in the NotePad sample application, * in the <em>samples/</em> directory of the SDK.</p> * * <p class="note"><strong>Note:</strong> this class assumes * monotonically increasing version numbers for upgrades. Also, there * is no concept of a database downgrade; installing a new version of * your app which uses a lower version number than a * previously-installed version will result in undefined behavior.</p> */ public abstract class SQLiteDatabaseHelper { private static final Logger LOG = LoggerFactory.getLogger(SQLiteDatabaseHelper.class); private final Context mContext; private final File mPath; private final CursorFactory mFactory; private final int mNewVersion; private SQLiteDatabase mDatabase = null; private boolean mIsInitializing = false; /** * Create a helper object to create, open, and/or manage a database. * This method always returns very quickly. The database is not actually * created or opened until one of {@link #getWritableDatabase} or * {@link #getReadableDatabase} is called. * * @param context to use to open or create the database * @param path of the database file, or null for an in-memory database * @param factory to use for creating cursor objects, or null for the default * @param version number of the database (starting at 1); if the database is older, * {@link #onUpgrade} will be used to upgrade the database */ public SQLiteDatabaseHelper(Context context, File path, CursorFactory factory, int version) { if (version < 1) throw new IllegalArgumentException("Version must be >= 1, was " + version); mContext = context; mPath = path; mFactory = factory; mNewVersion = version; } /** * Create and/or open a database that will be used for reading and writing. * The first time this is called, the database will be opened and * {@link #onCreate}, {@link #onUpgrade} and/or {@link #onOpen} will be * called. * * <p>Once opened successfully, the database is cached, so you can * call this method every time you need to write to the database. * (Make sure to call {@link #close} when you no longer need the database.) * Errors such as bad permissions or a full disk may cause this method * to fail, but future attempts may succeed if the problem is fixed.</p> * * <p class="caution">Database upgrade may take a long time, you * should not call this method from the application main thread, including * from {@link android.content.ContentProvider#onCreate ContentProvider.onCreate()}. * * @throws SQLiteException if the database cannot be opened for writing * @return a read/write database object valid until {@link #close} is called */ public synchronized SQLiteDatabase getWritableDatabase() { if (mDatabase != null && mDatabase.isOpen() && !mDatabase.isReadOnly()) { return mDatabase; // The database is already open for business } if (mIsInitializing) { throw new IllegalStateException("getWritableDatabase called recursively"); } boolean success = false; SQLiteDatabase db = null; try { mIsInitializing = true; if (mPath == null) { db = SQLiteDatabase.create(null); } else { db = mContext.openOrCreateDatabase(mPath.getName(), 0, mFactory); } int version = db.getVersion(); if (version != mNewVersion) { db.beginTransaction(); try { if (version == 0) { onCreate(db); } else { if (version > mNewVersion) { LOG.warn("Can't downgrade read-only database from version " + version + " to " + mNewVersion + ": " + db.getPath()); } onUpgrade(db, version, mNewVersion); } db.setVersion(mNewVersion); db.setTransactionSuccessful(); } finally { db.endTransaction(); } } onOpen(db); success = true; return db; } finally { mIsInitializing = false; if (success) { if (mDatabase != null) { try { mDatabase.close(); } catch (Exception e) { } } mDatabase = db; } else { if (db != null) db.close(); } } } /** * Create and/or open a database. This will be the same object returned by * {@link #getWritableDatabase} unless some problem, such as a full disk, * requires the database to be opened read-only. In that case, a read-only * database object will be returned. If the problem is fixed, a future call * to {@link #getWritableDatabase} may succeed, in which case the read-only * database object will be closed and the read/write object will be returned * in the future. * * <p class="caution">Like {@link #getWritableDatabase}, this method may * take a long time to return, so you should not call it from the * application main thread, including from * {@link android.content.ContentProvider#onCreate ContentProvider.onCreate()}. * * @throws SQLiteException if the database cannot be opened * @return a database object valid until {@link #getWritableDatabase} * or {@link #close} is called. */ public synchronized SQLiteDatabase getReadableDatabase() { if (mDatabase != null && mDatabase.isOpen()) { return mDatabase; // The database is already open for business } if (mIsInitializing) { throw new IllegalStateException("getReadableDatabase called recursively"); } try { return getWritableDatabase(); } catch (SQLiteException e) { if (mPath.getName() == null) throw e; // Can't open a temp database read-only! LOG.warn("Couldn't open " + mPath.getName() + " for writing (will try read-only):", e); } SQLiteDatabase db = null; try { mIsInitializing = true; db = SQLiteDatabase.openDatabase(mPath.toString(), mFactory, SQLiteDatabase.OPEN_READONLY); if (db.getVersion() != mNewVersion) { throw new SQLiteException("Can't upgrade read-only database from version " + db.getVersion() + " to " + mNewVersion + ": " + mPath); } onOpen(db); LOG.warn("Opened " + mPath.getName() + " in read-only mode"); mDatabase = db; return mDatabase; } finally { mIsInitializing = false; if (db != null && db != mDatabase) db.close(); } } /** * Close any open database object. */ public synchronized void close() { if (mIsInitializing) throw new IllegalStateException("Closed during initialization"); if (mDatabase != null && mDatabase.isOpen()) { mDatabase.close(); mDatabase = null; } } /** * Called when the database is created for the first time. This is where the * creation of tables and the initial population of the tables should happen. * * @param db The database. */ public abstract void onCreate(SQLiteDatabase db); /** * Called when the database needs to be upgraded. The implementation * should use this method to drop tables, add tables, or do anything else it * needs to upgrade to the new schema version. * * <p>The SQLite ALTER TABLE documentation can be found * <a href="http://sqlite.org/lang_altertable.html">here</a>. If you add new columns * you can use ALTER TABLE to insert them into a live table. If you rename or remove columns * you can use ALTER TABLE to rename the old table, then create the new table and then * populate the new table with the contents of the old table. * * @param db The database. * @param oldVersion The old database version. * @param newVersion The new database version. */ public abstract void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion); /** * Called when the database has been opened. The implementation * should check {@link SQLiteDatabase#isReadOnly} before updating the * database. * * @param db The database. */ public void onOpen(SQLiteDatabase db) {} }