io.permazen.core

Class SnapshotTransaction

java.lang.Object

io.permazen.core.Transaction

io.permazen.core.SnapshotTransaction

All Implemented Interfaces:

Closeable, AutoCloseable

public class SnapshotTransaction
extends Transaction
implements Closeable

A "snapshot" Transaction that persists indefinitely.

SnapshotTransactions hold a "snapshot" of some portion of the state of a Transaction for later use. Each SnapshotTransaction contains its own set of "snapshot" objects.

SnapshotTransactions can never be closed (i.e., committed or rolled-back); they persist in memory until no longer referenced. Transaction.Callbacks may be registered but they will never be invoked.

SnapshotTransactions can be based on an arbitrary KVStore; see Database.createSnapshotTransaction().

See Also:

Transaction.createSnapshotTransaction(), Database.createSnapshotTransaction(), SnapshotJTransaction

Nested Class Summary

Nested classes/interfaces inherited from class io.permazen.core.Transaction

Transaction.Callback, Transaction.CallbackAdapter, Transaction.ListenerSet

Field Summary

Fields inherited from class io.permazen.core.Transaction

log

Method Summary

Modifier and Type	Method and Description
void	addCallback(Transaction.Callback callback) Register a transaction callback to be invoked when this transaction completes.
void	close() Close this instance and release any resources associated with it.
void	commit() Commit this transaction.
KVStore	getKVStore() Get the underlying KVStore that holds this snapshot transaction's state.
boolean	isSnapshot() Determine whether this instance is a SnapshotTransaction.
boolean	isValid() Determine whether this transaction is still valid.
void	reset() Delete all objects contained in this snapshot transaction.
void	rollback() Roll back this transaction.

Methods inherited from class io.permazen.core.Transaction

addCreateListener, addDeleteListener, addFieldChangeListener, addListFieldChangeListener, addMapFieldChangeListener, addSetFieldChangeListener, addSimpleFieldChangeListener, addVersionChangeListener, adjustCounterField, copy, create, create, create, create, createSnapshotTransaction, delete, deleteSchemaVersion, exists, followReferencePath, generateId, getAll, getAll, getDatabase, getKey, getKey, getKVTransaction, getSchema, getSchemas, getSchemaVersion, getTypeDescription, getUserObject, invertReferencePath, isReadOnly, isRollbackOnly, queryCompositeIndex, queryCompositeIndex2, queryCompositeIndex3, queryCompositeIndex4, queryIndex, queryListElementIndex, queryMapValueIndex, queryVersion, readCounterField, readListField, readMapField, readSetField, readSimpleField, removeCreateListener, removeDeleteListener, removeFieldChangeListener, removeListFieldChangeListener, removeMapFieldChangeListener, removeSetFieldChangeListener, removeSimpleFieldChangeListener, removeVersionChangeListener, setListeners, setReadOnly, setRollbackOnly, setTimeout, setUserObject, snapshotListeners, updateSchemaVersion, writeCounterField, writeSimpleField

Methods inherited from class java.lang.Object

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

Method Detail

isSnapshot

public boolean isSnapshot()

Description copied from class: Transaction

Determine whether this instance is a SnapshotTransaction.

Overrides:

isSnapshot in class Transaction

Returns:

true if this instance is a SnapshotTransaction, otherwise false

getKVStore

public KVStore getKVStore()

Get the underlying KVStore that holds this snapshot transaction's state.

Returns:

underlying KVStore

reset

public void reset()

Delete all objects contained in this snapshot transaction.

Upon return, the underlying key/value store will still contain meta-data, but no objects.

commit

public void commit()

Commit this transaction.

SnapshotTransactions do not support this method and will always throw UnsupportedOperationException.

Overrides:

commit in class Transaction

Throws:

UnsupportedOperationException - always

rollback

public void rollback()

Roll back this transaction.

SnapshotTransactions do not support this method and will always throw UnsupportedOperationException.

Overrides:

rollback in class Transaction

Throws:

UnsupportedOperationException - always

addCallback

public void addCallback(Transaction.Callback callback)

Register a transaction callback to be invoked when this transaction completes.

Transaction.Callbacks registered with a SnapshotTransaction will by definition never be invoked. Therefore, this method simply discards callback.

Overrides:

addCallback in class Transaction

Parameters:

callback - callback to invoke

isValid

public boolean isValid()

Determine whether this transaction is still valid.

SnapshotTransactions are always valid.

Overrides:

isValid in class Transaction

Returns:

true always

close

public void close()

Close this instance and release any resources associated with it.

The implementation in SnapshotTransaction closes the underlying KVStore if it is a CloseableKVStore, otherwise it does nothing.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable