GreenDao3.0数据库升级保留原始数据的解决方法

/**
* 数据库管理工具
*/
public class DBManager {
private DaoMaster.DevOpenHelper devOpenHelper;
private static DBManager instance;
private static final String DB_NAME = "test.db";

private DBManager() {
devOpenHelper = new DBOpenHelper(MyApplication.getInstance(), DB_NAME);
}

public static DBManager getInstance() {
if (instance == null) {
instance = new DBManager();
}
return instance;
}

public SQLiteDatabase getWritableDatabase() {
if (devOpenHelper == null) {
devOpenHelper = new DBOpenHelper(MyApplication.getInstance(), DB_NAME);
}
SQLiteDatabase db = devOpenHelper.getWritableDatabase();
return db;
}

}

/**
* 实现GreenDao数据库升级保留原始交易数据
*/
public class DBMigrationHelper {
private static final String TAG = "DBMigrationHelper";

//DB中约束为NOT NULL的数据类型
List<Class> notNullClasses = Arrays.<Class>asList(boolean.class, byte.class, char.class,
short.class, int.class, long.class, float.class, double.class,
Boolean.class, Byte.class, Character.class, Short.class, Integer.class, Long.class,
Float.class, Double.class);

private Database db;
private Collection<AbstractDao<?, ?>> allDaos;

public DBMigrationHelper(SQLiteDatabase database) {
db = new StandardDatabase(database);
DaoMaster master = new DaoMaster(database);
DaoSession session = master.newSession(IdentityScopeType.None);
allDaos = session.getAllDaos();
}

/** 更改表结构，将旧表数据导入新表 */
public void upgradeTablesScheme() {
for (AbstractDao<?, ?> dao : allDaos) {
@SuppressWarnings("unchecked")
Class<? extends AbstractDao<?, ?>> daoCls = (Class<? extends AbstractDao<?, ?>>) dao.getClass();
handleUpgradeTableScheme(db, daoCls);
}
}

/** 删除临时表 */
public void dropTempTables() {
for (AbstractDao<?, ?> dao : allDaos) {
@SuppressWarnings("unchecked")
Class<? extends AbstractDao<?, ?>> daoCls = (Class<? extends AbstractDao<?, ?>>) dao.getClass();
dropTempTable(db, daoCls);
}
}

/** 执行表结构变更 */
private void handleUpgradeTableScheme(Database db, Class<? extends AbstractDao<?, ?>> daoCls) {
DaoConfig daoConfig = new DaoConfig(db, daoCls);
String tableName = daoConfig.tablename;
String tempTableName = tableName + "_TEMP";
//重命名表
db.execSQL("ALTER TABLE " + tableName + " RENAME TO " + tempTableName);
//创建新表
createTable(daoCls, db, true);

List<String> oldColumns = getColumns(db, tempTableName);
List<String> shareColumns = new ArrayList<>();
List<String> newNotNullColumns = new ArrayList<>();
for (Property property : daoConfig.properties) {
if (oldColumns.contains(property.columnName)) {
shareColumns.add(property.columnName);
} else if (checkNotNull(property)) {
newNotNullColumns.add(property.columnName);
}
}

//将旧表数据导入新表
String insertSQL = "INSERT INTO " + tableName + "("
+ TextUtils.join(",", shareColumns);
if (!newNotNullColumns.isEmpty()) {
insertSQL += ",";
insertSQL += TextUtils.join(",", newNotNullColumns);
}
insertSQL += ") SELECT ";
insertSQL += TextUtils.join(",", shareColumns);

String notNullStr = "";
for (String column : newNotNullColumns) {
notNullStr += ",0 AS " + column;
}
insertSQL += notNullStr;
insertSQL += " FROM " + tempTableName;

db.execSQL(insertSQL);
}

/** 是否是非空列 */
private boolean checkNotNull(Property property) {
return notNullClasses.contains(property.type);
}

/** 删除旧表 */
private void dropTempTable(Database db, Class<? extends AbstractDao<?, ?>> daoCls) {
DaoConfig daoConfig = new DaoConfig(db, daoCls);
String tableName = daoConfig.tablename;
String tempTableName = tableName + "_TEMP";
//删除旧表
db.execSQL("DROP TABLE " + tempTableName);
}

/** 获取数据库所有列名称 */
private static List<String> getColumns(Database db, String tableName) {
List<String> columns = new ArrayList<>();
Cursor cursor = null;
try {
cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 1", null);
if (cursor != null) {
Collections.addAll(columns, cursor.getColumnNames());
}
} catch (Exception e) {
Log.v(tableName, e.getMessage(), e);
e.printStackTrace();
} finally {
if (cursor != null) {
cursor.close();
}
}
return columns;
}

/** 创建表 */
private static void createTable(Class<? extends AbstractDao<?, ?>> daoCls, Database db, boolean b) {
reflectMethod(daoCls, "createTable", db, b);
}

/**
* 反射createTable或dropTable方法
*/
private static void reflectMethod(@NonNull Class<? extends AbstractDao<?, ?>> daoCls,
String methodName, Database db, boolean isExists) {
try {
Method method = daoCls.getDeclaredMethod(methodName, Database.class, boolean.class);
method.invoke(null, db, isExists);
} catch (NoSuchMethodException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}

/** 数据库升级接口，自定义升级时可实现本接口 */
public interface IDBMigration {

void onMigrate(SQLiteDatabase db);
}

/**
* <pre>
* V35版本数据库升级类,升级内容如下：
* </pre>
*/
public static class DBMigration_35 implements IDBMigration {
@Override
public void onMigrate(SQLiteDatabase db) {
Database database = new StandardDatabase(db);
//TODO   具体实现
}
}

/**
* <pre>
* V40版本数据库升级类,升级内容如下：
* </pre>
*/
public static class DBMigration_40 implements IDBMigration {
@Override
public void onMigrate(SQLiteDatabase db) {
//TODO  具体实现
}
}
}

/**
* 数据库帮助类，重写了数据库升级操作,不删表保留原交易数据
*/
public class DBOpenHelper extends DaoMaster.DevOpenHelper {
private static final String TAG = "DBOpenHelper";

public DBOpenHelper(Context context, String name) {
super(context, name);
}

@Override
public void onCreate(SQLiteDatabase db) {
DaoMaster.createAllTables(new StandardDatabase(db), false);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
try {
if (newVersion > oldVersion) {
//更改表结构
DBMigrationHelper helper = new DBMigrationHelper(db);
helper.upgradeTablesScheme();

for (int i = oldVersion + 1; i <= newVersion; i++) {
//获取不同数据库版本对应的迁移方法
//当用户跨版本升级时，依次执行每个版本对应的升级方法
Method method = getMigrationMethod(i);
if (method != null) {
method.invoke(this, db);
}
}

//删除临时表
helper.dropTempTables();
}
} catch (Exception e) {
e.printStackTrace();
Log.e(TAG, "DB onUpgrade failed:" + e.getMessage());
}
}

/**
* 获取数据库版本对应的迁移方法
* 数据库迁移方法命名格式为 migration_Scheme,其中
* Scheme为每个数据库版本的版本号
*/
private Method getMigrationMethod(int version) {
try {
return getClass().getDeclaredMethod("migration_" + version, SQLiteDatabase.class);
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
return null;
}

/** V35版本数据库升级 */
@SuppressWarnings("unused")
private void migration_35(SQLiteDatabase db) {
IDBMigration migration = new DBMigration_35();
migration.onMigrate(db);
}

/** V40版本数据库升级 */
@SuppressWarnings("unused")
private void migration_40(SQLiteDatabase db) {
IDBMigration migration = new DBMigration_40();
migration.onMigrate(db);
}
}