我已经创建了一个数据库。我想要进行交易。在
当用户调用
请参考我的代码：
同样，还有其他声明。
DBAdapter 代码如下：
这是完整的代码：
SaveCustomer()中，同时包含将记录插入Customer, CustomerControl, Profile, Payment表的多个语句。当用户调用
SaveCustomer()方法时，数据将存储到这4个表中。那么我该如何进行交易呢？如果一个表的插入失败，则需要回滚所有操作。例如，当第3个表插入记录时出现错误，则需要回滚前两个表的插入记录。请参考我的代码：
public void saveCustomer(){
DBAdapter dbAdapter = DBAdapter.getDBAdapterInstance(RetailerOrderKeyActivity.this);
dbAdapter.openDataBase();
ContentValues initialValues = new ContentValues();
initialValues.put("CustomerName",customer.getName());
initialValues.put("Address",customer.getAddress());
initialValues.put("CustomerPID",strPID);
initialValues.put("Date",strDateOnly);
long n = dbAdapter.insertRecordsInDB("Customer", null, initialValues);
}
同样，还有其他声明。
DBAdapter 代码如下：
public long insertRecordsInDB(String tableName, String nullColumnHack,ContentValues initialValues) {
long n =-1;
try {
myDataBase.beginTransaction();
n = myDataBase.insert(tableName, nullColumnHack, initialValues);
myDataBase.endTransaction();
myDataBase.setTransactionSuccessful();
} catch (Exception e) {
// how to do the rollback
e.printStackTrace();
}
return n;
}
这是完整的代码：
public class DBAdapter extends SQLiteOpenHelper {
private static String DB_PATH = "/data/data/com.my.controller/databases/";
private static final String DB_NAME = "customer";
private SQLiteDatabase myDataBase;
private final Context myContext;
private static DBAdapter mDBConnection;
private DBAdapter(Context context) {
super(context, DB_NAME, null, 1);
this.myContext = context;
DB_PATH = "/data/data/"
+ context.getApplicationContext().getPackageName()
+ "/databases/";
// The Android's default system path of your application database is
// "/data/data/mypackagename/databases/"
}
public static synchronized DBAdapter getDBAdapterInstance(Context context) {
if (mDBConnection == null) {
mDBConnection = new DBAdapter(context);
}
return mDBConnection;
}
public void createDataBase() throws IOException {
boolean dbExist = checkDataBase();
if (dbExist) {
// do nothing - database already exist
} else {
// By calling following method
// 1) an empty database will be created into the default system path of your application
// 2) than we overwrite that database with our database.
this.getReadableDatabase();
try {
copyDataBase();
} catch (IOException e) {
throw new Error("Error copying database");
}
}
}
private boolean checkDataBase() {
SQLiteDatabase checkDB = null;
try {
String myPath = DB_PATH + DB_NAME;
checkDB = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READONLY);
} catch (SQLiteException e) {
// database does't exist yet.
}
if (checkDB != null) {
checkDB.close();
}
return checkDB != null ? true : false;
}
private void copyDataBase() throws IOException {
InputStream myInput = myContext.getAssets().open(DB_NAME);
String outFileName = DB_PATH + DB_NAME;
OutputStream myOutput = new FileOutputStream(outFileName);
byte[] buffer = new byte[1024];
int length;
while ((length = myInput.read(buffer)) > 0) {
myOutput.write(buffer, 0, length);
}
// Close the streams
myOutput.flush();
myOutput.close();
myInput.close();
}
/**
* Open the database
* @throws SQLException
*/
public void openDataBase() throws SQLException {
String myPath = DB_PATH + DB_NAME;
myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);
}
@Override
public synchronized void close() {
if (myDataBase != null)
myDataBase.close();
super.close();
}
/**
* Call on creating data base for example for creating tables at run time
*/
@Override
public void onCreate(SQLiteDatabase db) {
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("ALTER TABLE WMPalmUploadControl ADD Testing int");
}
public void upgradeDb(){
onUpgrade(myDataBase, 1, 2);
}
public Cursor selectRecordsFromDB(String tableName, String[] tableColumns,
String whereClase, String whereArgs[], String groupBy,
String having, String orderBy) {
return myDataBase.query(tableName, tableColumns, whereClase, whereArgs,
groupBy, having, orderBy);
}
public ArrayList<ArrayList<String>> selectRecordsFromDBList(String tableName, String[] tableColumns,
String whereClase, String whereArgs[], String groupBy,
String having, String orderBy) {
ArrayList<ArrayList<String>> retList = new ArrayList<ArrayList<String>>();
ArrayList<String> list = new ArrayList<String>();
Cursor cursor = myDataBase.query(tableName, tableColumns, whereClase, whereArgs,
groupBy, having, orderBy);
if (cursor.moveToFirst()) {
do {
list = new ArrayList<String>();
for(int i=0; i<cursor.getColumnCount(); i++){
list.add( cursor.getString(i) );
}
retList.add(list);
} while (cursor.moveToNext());
}
if (cursor != null && !cursor.isClosed()) {
cursor.close();
}
return retList;
}
public long insertRecordsInDB(String tableName, String nullColumnHack,ContentValues initialValues) {
long n =-1;
try {
myDataBase.beginTransaction();
n = myDataBase.insert(tableName, nullColumnHack, initialValues);
myDataBase.endTransaction();
myDataBase.setTransactionSuccessful();
} catch (Exception e) {
// how to do the rollback
e.printStackTrace();
}
return n;
}
public boolean updateRecordInDB(String tableName,
ContentValues initialValues, String whereClause, String whereArgs[]) {
return myDataBase.update(tableName, initialValues, whereClause,
whereArgs) > 0;
}
public int updateRecordsInDB(String tableName,
ContentValues initialValues, String whereClause, String whereArgs[]) {
return myDataBase.update(tableName, initialValues, whereClause, whereArgs);
}
public int deleteRecordInDB(String tableName, String whereClause,
String[] whereArgs) {
return myDataBase.delete(tableName, whereClause, whereArgs);
}
public Cursor selectRecordsFromDB(String query, String[] selectionArgs) {
return myDataBase.rawQuery(query, selectionArgs);
}
public ArrayList<ArrayList<String>> selectRecordsFromDBList(String query, String[] selectionArgs) {
ArrayList<ArrayList<String>> retList = new ArrayList<ArrayList<String>>();
ArrayList<String> list = new ArrayList<String>();
Cursor cursor = myDataBase.rawQuery(query, selectionArgs);
if (cursor.moveToFirst()) {
do {
list = new ArrayList<String>();
for(int i=0; i<cursor.getColumnCount(); i++){
list.add( cursor.getString(i) );
}
retList.add(list);
} while (cursor.moveToNext());
}
if (cursor != null && !cursor.isClosed()) {
cursor.close();
}
return retList;
}
}
如果在插入表数据时出现任何问题，我希望能够回滚。
请帮助我。
谢谢。
我看到了这个相关的问题：
endTransaction放在finally块中，而不是try块中。 - VansFannel