/*
* 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 org.odk.collect.android.database;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
import android.database.sqlite.SQLiteException;
import android.util.Log;
/**
* We've taken this from Android's SQLiteOpenHelper. However, we can't appropriately lock the
* database so there may be issues if a thread opens the database read-only and another thread tries
* to open the database read/write. I don't think this will ever happen in ODK, though. (fingers
* crossed).
*/
/**
* A helper class to manage database creation and version management. 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>
* For an example, see the NotePadProvider class in the NotePad sample application, in the
* <em>samples/</em> directory of the SDK.
* </p>
*/
public abstract class ODKSQLiteOpenHelper {
private static final String t = ODKSQLiteOpenHelper.class.getSimpleName();
private final String mPath;
private final String mName;
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. The database is not
* actually created or opened until one of {@link #getWritableDatabase} or
* {@link #getReadableDatabase} is called.
*
* @param path to the file
* @param name 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 ODKSQLiteOpenHelper(String path, String name, CursorFactory factory, int version) {
if (version < 1)
throw new IllegalArgumentException("Version must be >= 1, was " + version);
mPath = path;
mName = name;
mFactory = factory;
mNewVersion = version;
}
/**
* Create and/or open a database that will be used for reading and writing. 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 it.
* <p>
* Errors such as bad permissions or a full disk may cause this operation to fail, but future
* attempts may succeed if the problem is fixed.
* </p>
*
* @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");
}
// If we have a read-only database open, someone could be using it
// (though they shouldn't), which would cause a lock to be held on
// the file, and our attempts to open the database read-write would
// fail waiting for the file lock. To prevent that, we acquire the
// lock on the read-only database, which shuts out other users.
boolean success = false;
SQLiteDatabase db = null;
// if (mDatabase != null) mDatabase.lock();
try {
mIsInitializing = true;
if (mName == null) {
db = SQLiteDatabase.create(null);
} else {
db = SQLiteDatabase.openOrCreateDatabase(mPath + "/" + mName, mFactory);
// db = mContext.openOrCreateDatabase(mName, 0, mFactory);
}
int version = db.getVersion();
if (version != mNewVersion) {
db.beginTransaction();
try {
if (version == 0) {
onCreate(db);
} else {
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.unlock();
}
mDatabase = db;
} else {
// if (mDatabase != null) mDatabase.unlock();
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.
*
* @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 (mName == null)
throw e; // Can't open a temp database read-only!
Log.e(t, "Couldn't open " + mName + " for writing (will try read-only):", e);
}
SQLiteDatabase db = null;
try {
mIsInitializing = true;
String path = mPath + "/" + mName;
// mContext.getDatabasePath(mName).getPath();
db = SQLiteDatabase.openDatabase(path, mFactory, SQLiteDatabase.OPEN_READONLY);
if (db.getVersion() != mNewVersion) {
throw new SQLiteException("Can't upgrade read-only database from version "
+ db.getVersion() + " to " + mNewVersion + ": " + path);
}
onOpen(db);
Log.w(t, "Opened " + mName + " 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. Override method should check
* {@link SQLiteDatabase#isReadOnly} before updating the database.
*
* @param db The database.
*/
public void onOpen(SQLiteDatabase db) {
}
}