Extending iBATIS - iBATIS in Action - page 282

■ TRANSACTION_READ_UNCOMMITTED
■ TRANSACTION_READ_COMMITTED
■ TRANSACTION_REPEATABLE_READ
■ TRANSACTION_SERIALIZABLE
■ TRANSACTION_NONE

Each of these is documented in the JDBC Connection API , and you can learn more
in chapter 7. The important thing to note here is that if your transaction manager
implementation does not support one or more of these, you should be sure to
throw an exception to let the developer know. Otherwise, there could be unex-
pected consequences that are difficult for your users to debug.
The next pair of methods are getDataSource() and setDataSource() . These
methods describe a JavaBeans property for the DataSource associated with this
TransactionConfig instance. Usually you won't have to do anything special with
the DataSource , but it is provided here so that you can decorate it with additional
behavior if you need to. Many transaction manager implementations wrap the
DataSource and the Connection objects it provides, to add transaction related
functionality to each of them.
The final pair of methods makes up another JavaBeans property that allows
the framework to configure a maximum number of concurrent transactions sup-
ported. Your implementation may or may not be configurable, but it is important
to ensure that you throw an appropriate exception if the number set is too high
for your system to handle.

12.5.2 Understanding the Transaction interface

Recall the factory method called newTransaction() on the TransactionConfig
class discussed in the previous section. The return value of that method is a
Transaction instance. The Transaction interface describes the behavior neces-
sary to support transactions within the iBATIS framework. It's a pretty typical set of
functionality, which will be familiar to anyone who has worked with transactions
before. The Transaction interface looks like this:

public interface Transaction {

public void commit() throws SQLException,
TransactionException;

public void rollback() throws SQLException,
TransactionException;