Package io.permazen

Class DetachedPermazenTransaction

java.lang.Object

io.permazen.PermazenTransaction

io.permazen.DetachedPermazenTransaction

All Implemented Interfaces:

Closeable, AutoCloseable

public class DetachedPermazenTransaction
extends PermazenTransaction
implements Closeable

A PermazenTransaction that is not actually connected to a Permazen database instance, but instead exists just to hold objects in memory.

DetachedPermazenTransactions are typically used to "snapshot" some portion of a normal PermazenTransaction for later use. As with all transactions, each DetachedPermazenTransaction contains its own object data.

For convenience, each PermazenTransaction has a default, initially empty DetachedPermazenTransaction instance associated with it; PermazenObject.copyOut() copies objects there.

Because DetachedPermazenTransactions live indefinitely, their objects can be used just like normal Java objects, outside of any regular transaction, yet all of the usual Permazen features such as indexing, listeners, validation, etc., continue to function normally.

Because they typically contain only a portion of the database's objects and therefore may have dangling references, the referential integrity function of @PermazenField.allowDeleted() is disabled in DetachedPermazenTransactions.

Other Uses

More general usage beyond copies of regular transactions is possible: an empty DetachedPermazenTransaction can be created on the fly via PermazenTransaction.createDetachedTransaction() and then used as simple in-memory transaction workspace. The resulting key/value pairs could then be (de)serialized and sent over the network; see for example PermazenObjectHttpMessageConverter.

For KVDatabase's that support it, using the key/value store snapshot returned by KVTransaction.readOnlySnapshot() allows an efficient "copy" of the entire database into a DetachedPermazenTransaction; see Permazen.createSnapshotTransaction().

Lifecycle Management

Instances of this class should be close()'d when no longer needed to release any associated resources.

See Also:

• PermazenTransaction.createDetachedTransaction()
• PermazenTransaction.createSnapshotTransaction()
• Permazen.createDetachedTransaction()
• DetachedTransaction

Method Summary

Modifier and Type	Method	Description
void	close()	Close this instance and release any resources associated with it.
void	commit()	Commit this transaction.
DetachedTransaction	getTransaction()	Get the DetachedTransaction associated with this instance.
final boolean	isDetached()	Determine whether this instance is a DetachedPermazenTransaction.
boolean	isOpen()	Determine whether this transaction is still valid.
void	reset()	Delete all objects contained in this detached transaction and reset it back to its initial state.
void	rollback()	Roll back this transaction.

Methods inherited from class io.permazen.PermazenTransaction

cascade, copyTo, copyTo, create, create, createDetachedTransaction, createSnapshotTransaction, delete, exists, followReferencePath, get, get, get, getAll, getCurrent, getDetachedTransaction, getKey, getPermazen, getValidationMode, invertReferencePath, migrateSchema, performAction, queryCompositeIndex, queryCompositeIndex, queryCompositeIndex, queryIndex, queryListElementIndex, queryMapValueIndex, querySchemaIndex, querySimpleIndex, readCounterField, readListField, readMapField, readSetField, readSimpleField, recreate, registerPermazenObject, resetValidationQueue, revalidate, setCurrent, validate, withWeakConsistency, writeSimpleField

Methods inherited from class java.lang.Object

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

Method Details

isDetached

public final boolean isDetached()

Description copied from class: PermazenTransaction

Determine whether this instance is a DetachedPermazenTransaction.

Overrides:

isDetached in class PermazenTransaction

Returns:

true if this instance is a DetachedPermazenTransaction, otherwise false

getTransaction

public DetachedTransaction getTransaction()

Get the DetachedTransaction associated with this instance.

Overrides:

getTransaction in class PermazenTransaction

Returns:

the associated core API detached transaction

reset

public void reset()

Delete all objects contained in this detached transaction and reset it back to its initial state.

It will contain schema meta-data but no objects.

commit

public void commit()

Commit this transaction.

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

Overrides:

commit in class PermazenTransaction

Throws:

UnsupportedOperationException - always

rollback

public void rollback()

Roll back this transaction.

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

Overrides:

rollback in class PermazenTransaction

Throws:

UnsupportedOperationException - always

isOpen

public boolean isOpen()

Determine whether this transaction is still valid.

DetachedPermazenTransactions are always valid.

Overrides:

isOpen in class PermazenTransaction

Returns:

true always

See Also:

• Transaction.isOpen()

close

public void close()

Close this instance and release any resources associated with it.

The implementation in DetachedPermazenTransactions closes the underlying DetachedTransaction.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

See Also:

• DetachedTransaction.close()