数据库-事务

//取消自动提交，开启事务
Connection#setAutoCommit(false);
//任务失败，回滚
Connection#rollback();
//提交任务
Connection#commit();

CREATE TABLE bank(
bid INT,
bname VARCHAR(12),
bmoney DOUBLE
)

INSERT INTO bank VALUES(1,'tom',1000)
INSERT INTO bank VALUES(2,'CC',1500)

void transaction() {
Connection connection = DBHelper.getConnection();
PreparedStatement preparedStatement = null;
ResultSet resultSet = null;
try {
// 取消自动提交，开启事务
connection.setAutoCommit(false);
String sql = "UPDATE  bank SET bmoney=bmoney-1000 WHERE bid=?";
preparedStatement = (PreparedStatement) connection
.prepareStatement(sql);
preparedStatement.setInt(1, 1);
int updateLine = 0;
updateLine = preparedStatement.executeUpdate();

String checkMoney = "SELECT bmoney from bank where bid=?";
preparedStatement = (PreparedStatement) connection
.prepareStatement(checkMoney);
preparedStatement.setInt(1, 1);
resultSet = preparedStatement.executeQuery();
double money = 0;
if (resultSet.next()) {
money = resultSet.getDouble("bmoney");
}

String getmoney = "UPDATE bank SET bmoney=bmoney+1000 WHERE bid=2";
preparedStatement = (PreparedStatement) connection
.prepareStatement(getmoney);
int getInt = 0;
getInt = preparedStatement.executeUpdate();

// 判断是否满足条件
if (updateLine > 0 && money >= 0 && getInt > 0) {
// 提交任务
connection.commit();
} else {
try {
// 任务失败，回滚
connection.rollback();
System.out.println("余额不足！！");
} catch (SQLException e1) {
e1.printStackTrace();
}
}

} catch (SQLException e) {
e.printStackTrace();
try {
// 任务失败，回滚
connection.rollback();
System.out.println("转账失败！！");
} catch (SQLException e1) {
e1.printStackTrace();
}
}
DBHelper.closeAll(connection, preparedStatement, resultSet);

}