A typical service class method looks like the following:

public void updateSomething(TransactionConfig tc, ...)
{
    try
    {
        TransactionHelper.begin(tc);
        ....
        TransactionHelper.commit(tc);
    }
    catch (Exception e)
    {
        TransactionHelper.rollback(tc);
        throw e;
    }
}

OR

public xxx getSomething(TransactionConfig tc, ...)
{
    try
    {
        TransactionHelper.begin(tc);
        ....
        return xxx;
    }
    finally
    {
        TransactionHelper.rollback(tc);
    }
}

The object TransactionConfig can be used to control how transaction is to be performed in the service call, e.g.

// Don't start a transaction.
getSomething(new TransactionConfig().doNotStartTransaction(), xxx);

// Use read-replica. This is recommended for retrieving past data set such as reports.
// Do NOT use read-replica for updates.
// This is only applicable for MySQL with read-replica setup.
getSomething(new TransactionConfig().useReadReplica(), xxx);

// Set timeout to 30min (much longer than the default).
getSomething(new TransactionConfig().timeout30min(), xxx);

// Don't start a transaction AND use read-replica and a 30min timeout.
getSomething(new TransactionConfig().doNotStartTransaction().useReadReplica().timeout30min(), xxx);

// No specific transaction configuration - apply default.
getSomething(new TransactionConfig(), xxx);
getSomething(null, xxx); // or simply pass null.