org.akubraproject.txn
Class AbstractTransactionalConnection

java.lang.Object
  org.akubraproject.impl.AbstractBlobStoreConnection
      org.akubraproject.txn.AbstractTransactionalConnection

All Implemented Interfaces:

Synchronization, org.akubraproject.BlobStoreConnection

Direct Known Subclasses:

SQLTransactionalConnection

public abstract class AbstractTransactionalConnection
extends org.akubraproject.impl.AbstractBlobStoreConnection
implements Synchronization

A basic superclass for transactional store connections. This implements the common blob-handling parts of a transactional connection, leaving subclasses to implement the transactional management of the id-mappings.

Subclasses must implement getRealId, remNameEntry, addNameEntry, listBlobIds, and override close; in addition they may want to override beforeCompletion and/or afterCompletion for pre- and post-commit/rollback processing.

The subclass is expected to implement id mapping, mapping upper-level blob-id's to underlying blob-id's; these mappings are managed via the remNameEntry and addNameEntry method, and getRealId is used to query the mapping.

Author:

Ronald Tschalär

Nested Class Summary

protected class

AbstractTransactionalConnection.TxnBlob A transactional blob implementation.

Field Summary

protected Map<URI,org.akubraproject.Blob>	blobCache a cache of blobs
protected org.akubraproject.BlobStoreConnection	bStoreCon the underlying blob-store that actually stores the blobs
protected List<URI>	delBlobs the list of underlying id's of deleted blobs
protected boolean	isCompleted Whether or not the current transaction has been completed yet
protected List<URI>	newBlobs the list of underlying id's of added blobs
protected Transaction	tx the transaction this connection belongs to

Fields inherited from class org.akubraproject.impl.AbstractBlobStoreConnection

closed, owner, streamManager

Constructor Summary

protected

AbstractTransactionalConnection(org.akubraproject.BlobStore owner, org.akubraproject.BlobStore bStore, Transaction tx, Map<String,String> hints) Create a new transactional connection.

Method Summary

protected void	addBlob(URI ourId, URI storeId) Add a blob to the underlying store.
protected abstract void	addNameEntry(URI ourId, URI storeId) Add an id mapping.
void	afterCompletion(int status) Invoked after the transaction has completed, i.e.
void	beforeCompletion() Invoked before the transaction is completed, i.e.
org.akubraproject.Blob	getBlob(URI blobId, Map<String,String> hints)
protected abstract URI	getRealId(URI blobId) Look up the underlying store's blob-id for the given upper-level blob-id.
protected void	remBlob(URI ourId, URI storeId) Remove a blob from the underlying store.
protected abstract void	remNameEntry(URI ourId, URI storeId) Remove an id mapping.
void	sync()
protected void	validateId(URI blobId) Check whether we can store this id.

Methods inherited from class org.akubraproject.impl.AbstractBlobStoreConnection

close, ensureOpen, getBlob, getBlobStore, isClosed

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.akubraproject.BlobStoreConnection

listBlobIds

Field Detail

bStoreCon

protected final org.akubraproject.BlobStoreConnection bStoreCon

the underlying blob-store that actually stores the blobs

tx

protected final Transaction tx

the transaction this connection belongs to

isCompleted

protected boolean isCompleted

Whether or not the current transaction has been completed yet

newBlobs

protected final List<URI> newBlobs

the list of underlying id's of added blobs

delBlobs

protected final List<URI> delBlobs

the list of underlying id's of deleted blobs

blobCache

protected final Map<URI,org.akubraproject.Blob> blobCache

a cache of blobs

Constructor Detail

AbstractTransactionalConnection

protected AbstractTransactionalConnection(org.akubraproject.BlobStore owner,
                                          org.akubraproject.BlobStore bStore,
                                          Transaction tx,
                                          Map<String,String> hints)
                                   throws IOException

Create a new transactional connection.

Parameters:

owner - the blob-store we belong to

bStore - the underlying blob-store to use

tx - the transaction we belong to

hints - A set of hints for the openConnection on the wrapped store

Throws:

IOException - if an error occurs initializing this connection

Method Detail

getBlob

public org.akubraproject.Blob getBlob(URI blobId,
                                      Map<String,String> hints)
                               throws IOException

Specified by:

getBlob in interface org.akubraproject.BlobStoreConnection

Throws:

IOException

sync

public void sync()
          throws IOException

Specified by:

sync in interface org.akubraproject.BlobStoreConnection

Throws:

IOException

validateId

protected void validateId(URI blobId)
                   throws org.akubraproject.UnsupportedIdException

Check whether we can store this id.

Parameters:

blobId - the upper level blob-id

Throws:

org.akubraproject.UnsupportedIdException - if the id cannot be stored

getRealId

protected abstract URI getRealId(URI blobId)
                          throws IOException

Look up the underlying store's blob-id for the given upper-level blob-id.

Parameters:

blobId - the upper level blob-id

Returns:

the underlying blob-id that blobId maps to, or null if no such mapping exists (i.e. blobId is not a known upper-level blob-id)

Throws:

IOException - if an error occurred looking up the id

remNameEntry

protected abstract void remNameEntry(URI ourId,
                                     URI storeId)
                              throws IOException

Remove an id mapping.

Parameters:

ourId - the upper-level blob-id

storeId - the underlying store's blob-id

Throws:

IOException - if an error occurred removing the mapping or the mapping does not exist

addNameEntry

protected abstract void addNameEntry(URI ourId,
                                     URI storeId)
                              throws IOException

Add an id mapping.

Parameters:

ourId - the upper-level blob-id to map

storeId - the underlying store's blob-id to map ourId to

Throws:

IOException - if an error occurred adding the mapping or the mapping already exists

remBlob

protected void remBlob(URI ourId,
                       URI storeId)
                throws IOException

Remove a blob from the underlying store. This implementation just updates the newBlobs and delBlobs lists; actual blob deletion is deferred till commit.

Parameters:

ourId - the upper-level blob-id

storeId - the underlying store's blob-id

Throws:

IOException - if an error occurred removing the blob or the blob does not exist

addBlob

protected void addBlob(URI ourId,
                       URI storeId)
                throws IOException

Add a blob to the underlying store. This implementation just updates the newBlobs list; actual blob writing is done via the blob itself..

Parameters:

ourId - the upper-level blob-id

storeId - the underlying store's blob-id

Throws:

IOException - if an error occurred removing the blob or the blob does not exist

beforeCompletion

public void beforeCompletion()

Invoked before the transaction is completed, i.e. before a rollback or commit is started. Whether or not this is called on a rollback may vary.

Specified by:

beforeCompletion in interface Synchronization

See Also:

Synchronization.beforeCompletion()

afterCompletion

public void afterCompletion(int status)

Invoked after the transaction has completed, i.e. after a rollback or commit has finished. This is always callled.

Subclasses that override this must make sure to invoke super.afterCompletion so that the cleanup code in this implementation is run. This implementation cleans up deleted or added blobs (depending on the outcome of the transaction).

Specified by:

afterCompletion in interface Synchronization

See Also:

Synchronization.afterCompletion(int)