oracle.olapi.transaction
Interface TransactionProvider

All Known Implementing Classes:

ExpressTransactionProvider

public interface TransactionProvider

This interface defines an OLAP transaction provider. The interface is not implemented by OLAP API application developers. The ExpressTransactionProvider class implements this interface for transactions with Oracle OLAP.

Creating a derived Source or changing the state of a Template occurs in a transaction context. A TransactionProvider ensures the following:

• A transaction is isolated from other transactions.
• If a transaction fails, its effects are undone (rolled back).
• The effects of a completed transaction persist.

A transaction is represented by an instance of the Transaction class. An application does not directly create new Transaction objects. Instead, a TransactionProvider supplies them as they are needed. Only one Transaction is the current Transaction at any one time. With the methods of a TransactionProvider, an application can get the current Transaction or set a previously saved Transaction as the current Transaction.

An application creates a derived Source or changes the state of a Template in the current Transaction. A Source or state change is active, or valid, in the Transaction in which in which it was created or modified, or in a child of that Transaction. Any changes that occur in the child Transaction do not take effect in the parent Transaction until the application calls the prepareCurrentTransaction and commitCurrentTransaction methods of the TransactionProvider. The only Source that can be modified is one produced by a Template and which therefore has a DynamicDefinition as a proxy for the ImmutableDefinition that is paired with the Source.

When the application calls the commitCurrentTransaction method, the state of the child Transaction moves up into the parent Transaction. The child Transaction disappears. The updated Transaction is still the parent Transaction for any other child Transaction of the original parent Transaction. If the application does not want to commit a child Transaction into the parent Transaction, then it can call the rollbackCurrentTransaction method. The TransactionProvider then discards any changes made in the child Transaction and makes the parent Transaction the current Transaction.

The following example illustrates a rollback.

 TransactionProvider transactionProvider = new ExpressTransactionProvider();
 // Save the top-level Transaction.
 Transaction parent = transactionProvider.getCurrentTransaction();
 // Begin a child Transaction.
 transactionProvider.beginSubtransaction();

 // The createCube() method returns a Source that was produced by a Template.
 // That Source represents the joining of a measure and some dimensions into a cube.
 // The context input parameter is an object that supplies a MetadataProvider and a
 // DataProvider for the cube Template to use to get primary Source objects and
 // derived Source objects.

 // Create a cube in the child Transaction.
 Source cube = createCube(context);
 // Save the child Transaction.
 Transaction child = transactionProvider.getCurrentTransaction();
 // Begin a grandchild Transaction.
 transactionProvider.beginSubtransaction();
 // Add another dimension as an edge.
 cube.addEdge(edge);
 // Discard the grandchild Transaction that added the edge.
 transactionProvider.rollbackCurrentTransaction();
 // Prepare and commit the child Transaction.
 transactionProvider.prepareCurrentTransaction();
 transactionProvider.commitCurrentTransaction();
 // The cube now exists in the parent Transaction.

A transaction is represented by one of the following two types of OLAP API Transaction objects:

• A read Transaction, in which an application can create a Cursor to fetch the data defined by a Source. The initial Transaction in an application is a read Transaction.
• A write Transaction, in which an application creates a derived Source or changes the state of a Template. A write Transaction is a child of a parent read Transaction. To move a Source or state change created in a write Transaction into its parent read Transaction, the application must call the prepareCurrentTransaction and commitCurrentTransaction methods.

The type of Transaction is not usually visible to an application. However, you should be aware of the types because some exceptions, such as WriteLockException, refer to the Transaction type.

The following is an example of how a TransactionProvider uses read and write Transaction objects.

• An application creates a derived Source by joining two primary Source objects.
• When the join call occurs, the TransactionProvider provides the current Transaction.
• Since this is the first operation that creates a derived Source, the type of Transaction is unassigned. The TransactionProvider makes it a read Transaction, transactionA.
• Since the join call creates a derived Source, sourceA, the application needs a write Transaction. The TransactionProvider creates a child Transaction, transactionB, of transactionA. The TransactionProvider makes transactionB a write Transaction.
• The application joins sourceA to a primary Source to create another derived Source, sourceB. Since the current Transaction is a write Transaction, this second join occurs in the same Transaction.
• The application then calls the prepareCurrentTransaction and commitCurrentTransaction methods. The state of child Transaction, transactionB, now moves up into the parent Transaction, transactionA. The transactionB Transaction disappears, leaving transactionA as the current Transaction. The Source objects created in transactionB are now active in transactionA.
• Since transactionA is a read Transaction, the application can create a Cursor for sourceA or sourceB, get the values from the Cursor, and display the data.

See Also:

Cursor, Source, Template

Method Summary

void	addTransactionListener( l) Registers a TransactionListener with this TransactionProvider.
Transaction	beginSubtransaction() Begins a child Transaction of the current Transaction.
void	commitCurrentTransaction() Moves the state of a child Transaction into the parent Transaction.
Transaction	getCurrentTransaction() Gets the current Transaction.
void	prepareCurrentTransaction() Prepares the current Transaction for committing.
void	removeTransactionListener( l) Unregisters a TransactionListener with this TransactionProvider.
void	rollbackCurrentTransaction() Rolls back, or undoes, any OLAP API operations the application performed in the current Transaction.
void	setCurrentTransaction(Transaction transaction) Specifies a Transaction as the current Transaction.

Method Detail

getCurrentTransaction

public Transaction getCurrentTransaction()

Gets the current Transaction.

Returns:

The current Transaction.

setCurrentTransaction

public void setCurrentTransaction(Transaction transaction)

Specifies a Transaction as the current Transaction.

Parameters:

transaction - A Transaction object to specify as the current Transaction.

prepareCurrentTransaction

public void prepareCurrentTransaction()
                               throws NotCommittableException,
                                      TransactionInactiveException

Prepares the current Transaction for committing. An application must call prepareCurrentTransaction before calling commitCurrentTransaction.

commitCurrentTransaction

public void commitCurrentTransaction()
                              throws NotPreparedException,
                                     TransactionInactiveException

Moves the state of a child Transaction into the parent Transaction. Before calling commitCurrentTransaction, an application must call prepareCurrentTransaction.

rollbackCurrentTransaction

public void rollbackCurrentTransaction()
                                throws NotPreparedException,
                                       TransactionInactiveException

Rolls back, or undoes, any OLAP API operations the application performed in the current Transaction. The TransactionProvider discards the operations the application performed in the child Transaction and makes the parent Transaction the current Transaction.

beginSubtransaction

public Transaction beginSubtransaction()
                                throws TransactionInactiveException

Begins a child Transaction of the current Transaction. The child Transaction becomes the current Transaction.

Returns:

A Transaction object that represents the current Transaction.

addTransactionListener

public void addTransactionListener( l)

Registers a TransactionListener with this TransactionProvider.

Parameters:

l - The TransactionListener to add to this TransactionProvider.

removeTransactionListener

public void removeTransactionListener( l)

Unregisters a TransactionListener with this TransactionProvider.

Parameters:

l - The TransactionListener to remove from the list of listeners for this TransactionProvider.