org.mapdb

Class Engine.ReadOnlyWrapper

java.lang.Object

org.mapdb.Engine.ReadOnly

org.mapdb.Engine.ReadOnlyWrapper

All Implemented Interfaces:

Closeable, AutoCloseable, Engine

Enclosing interface:

Engine

public static final class Engine.ReadOnlyWrapper
extends Engine.ReadOnly

Wraps an Engine and throws UnsupportedOperationException("Read-only") on any modification attempt.

Nested Class Summary

Nested classes/interfaces inherited from interface org.mapdb.Engine

Engine.CloseOnJVMShutdown, Engine.ReadOnly, Engine.ReadOnlyWrapper

Field Summary

Fields

Modifier and Type	Field and Description
protected Engine	engine

Fields inherited from interface org.mapdb.Engine

CLOSED_ENGINE, RECID_CLASS_CATALOG, RECID_FIRST, RECID_LAST_RESERVED, RECID_NAME_CATALOG, RECID_RECORD_CHECK

Constructor Summary

Constructors

Constructor and Description
Engine.ReadOnlyWrapper(Engine engine)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	canRollback()
boolean	canSnapshot()
void	clearCache() clears any underlying cache
void	close() Close store/cache.
<A> A	get(long recid, Serializer<A> serializer) Get existing record.
Engine	getWrappedEngine() if this is wrapper return underlying engine, or null
boolean	isClosed() Checks whether Engine was closed.
Engine	snapshot() Returns read-only snapshot of data in Engine.

Methods inherited from class org.mapdb.Engine.ReadOnly

commit, compact, compareAndSwap, delete, isReadOnly, preallocate, put, rollback, update

Methods inherited from class java.lang.Object

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

Field Detail

engine

protected final Engine engine

Constructor Detail

Engine.ReadOnlyWrapper

public Engine.ReadOnlyWrapper(Engine engine)

Method Detail

get

public <A> A get(long recid,
        Serializer<A> serializer)

Description copied from interface: Engine

Get existing record.

Recid must be a number returned by 'put' method. Behaviour for invalid recid (random number or already deleted record) is not defined, typically it returns null or throws 'EndOfFileException'

Parameters:

recid - (record identifier) under which record was persisted

serializer - used to deserialize record from binary form

Returns:

record matching given recid, or null if record is not found under given recid.

close

public void close()

Description copied from interface: Engine

Close store/cache. This method must be called before JVM exits to flush all caches and prevent store corruption. Also it releases resources used by MapDB (disk, memory..).

Engine can no longer be used after this method was called. If Engine is used after closing, it may throw any exception including NullPointerException

There is an configuration option DBMaker.Maker.closeOnJvmShutdown() which uses shutdown hook to automatically close Engine when JVM shutdowns.

isClosed

public boolean isClosed()

Description copied from interface: Engine

Checks whether Engine was closed.

Returns:

true if engine was closed

canRollback

public boolean canRollback()

Returns:

true if engine supports rollback

getWrappedEngine

public Engine getWrappedEngine()

Description copied from interface: Engine

if this is wrapper return underlying engine, or null

clearCache

public void clearCache()

Description copied from interface: Engine

clears any underlying cache

canSnapshot

public boolean canSnapshot()

Returns:

true if engine can create read-only snapshots

snapshot

public Engine snapshot()
                throws UnsupportedOperationException

Description copied from interface: Engine

Returns read-only snapshot of data in Engine.

Throws:

UnsupportedOperationException - if snapshots are not supported/enabled