org.mapdb
Class EngineWrapper.ReadOnlyEngine

java.lang.Object
  org.mapdb.EngineWrapper
      org.mapdb.EngineWrapper.ReadOnlyEngine

All Implemented Interfaces:

Engine

Enclosing class:

EngineWrapper

public static class EngineWrapper.ReadOnlyEngine
extends EngineWrapper

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

Nested Class Summary

Nested classes/interfaces inherited from class org.mapdb.EngineWrapper

EngineWrapper.CloseOnJVMShutdown, EngineWrapper.ImmutabilityCheckEngine, EngineWrapper.ReadOnlyEngine, EngineWrapper.SerializerCheckEngineWrapper, EngineWrapper.SynchronizedEngineWrapper

Field Summary

Fields inherited from class org.mapdb.EngineWrapper

CLOSED

Fields inherited from interface org.mapdb.Engine

CATALOG_RECID, CHECK_RECORD, CLASS_INFO_RECID, LAST_RESERVED_RECID

Constructor Summary

EngineWrapper.ReadOnlyEngine(Engine engine)

Method Summary

boolean	canSnapshot()
void	commit() Makes all changes made since the previous commit/rollback permanent.
<A> boolean	compareAndSwap(long recid, A expectedOldValue, A newValue, Serializer<A> serializer) Updates existing record in atomic (Compare And Swap) manner.
<A> void	delete(long recid, Serializer<A> serializer) Remove existing record from store/cache Recid must be a number returned by 'put' method.
boolean	isReadOnly() Check if you can write into this Engine.
long	preallocate() Preallocates recid for not yet created record.
void	preallocate(long[] recids) Preallocates recids for not yet created record.
<A> long	put(A value, Serializer<A> serializer) Insert new record.
void	rollback() Undoes all changes made in the current transaction.
Engine	snapshot() Returns read-only snapshot of data in Engine.
<A> void	update(long recid, A value, Serializer<A> serializer) Update existing record with new value.

Methods inherited from class org.mapdb.EngineWrapper

canRollback, checkClosed, clearCache, close, closeListenerRegister, closeListenerUnregister, compact, get, getSerializerPojo, getWrappedEngine, isClosed

Methods inherited from class java.lang.Object

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

Constructor Detail

EngineWrapper.ReadOnlyEngine

public EngineWrapper.ReadOnlyEngine(Engine engine)

Method Detail

preallocate

public long preallocate()

Description copied from interface: Engine

Preallocates recid for not yet created record. It does not insert any data into it.

Specified by:

preallocate in interface Engine

Overrides:

preallocate in class EngineWrapper

Returns:

new recid

preallocate

public void preallocate(long[] recids)

Description copied from interface: Engine

Preallocates recids for not yet created record. It does not insert any data into it. This is done in batch of given size (determied by size of array in argument)

Specified by:

preallocate in interface Engine

Overrides:

preallocate in class EngineWrapper

Parameters:

recids - array to put result into

compareAndSwap

public <A> boolean compareAndSwap(long recid,
                                  A expectedOldValue,
                                  A newValue,
                                  Serializer<A> serializer)

Description copied from interface: Engine

Updates existing record in atomic (Compare And Swap) manner. Value is modified only if old value matches expected value. There are three ways to match values, MapDB may use any of them:

1. Equality check oldValue==expectedOldValue when old value is found in instance cache
2. Deserializing oldValue using serializer and checking oldValue.equals(expectedOldValue)
3. Serializing expectedOldValue using serializer and comparing binary array with already serialized oldValue

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

Specified by:

compareAndSwap in interface Engine

Overrides:

compareAndSwap in class EngineWrapper

Parameters:

recid - (record identifier) under which record was persisted.

expectedOldValue - old value to be compared with existing record

newValue - to be written if values are matching

serializer - used to serialize record into binary form

Returns:

true if values matched and newValue was written

put

public <A> long put(A value,
                    Serializer<A> serializer)

Description copied from interface: Engine

Insert new record.

Specified by:

put in interface Engine

Overrides:

put in class EngineWrapper

Parameters:

value - records to be added

serializer - used to convert record into/from binary form

Returns:

recid (record identifier) under which record is stored.

update

public <A> void update(long recid,
                       A value,
                       Serializer<A> serializer)

Description copied from interface: Engine

Update existing record with new value.

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

Specified by:

update in interface Engine

Overrides:

update in class EngineWrapper

Parameters:

recid - (record identifier) under which record was persisted.

value - new record value to be stored

serializer - used to serialize record into binary form

delete

public <A> void delete(long recid,
                       Serializer<A> serializer)

Description copied from interface: Engine

Remove existing record from store/cache

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

Specified by:

delete in interface Engine

Overrides:

delete in class EngineWrapper

Parameters:

recid - (record identifier) under which was record persisted

serializer - which may be used in some circumstances to deserialize and store old object

commit

public void commit()

Description copied from interface: Engine

Makes all changes made since the previous commit/rollback permanent. In transactional mode (on by default) it means creating journal file and replaying it to storage. In other modes it may flush disk caches or do nothing at all (check your config options)

Specified by:

commit in interface Engine

Overrides:

commit in class EngineWrapper

rollback

public void rollback()

Description copied from interface: Engine

Undoes all changes made in the current transaction. If transactions are disabled it throws UnsupportedOperationException.

Specified by:

rollback in interface Engine

Overrides:

rollback in class EngineWrapper

isReadOnly

public boolean isReadOnly()

Description copied from interface: Engine

Check if you can write into this Engine. It may be readonly in some cases (snapshot, read-only files).

Specified by:

isReadOnly in interface Engine

Overrides:

isReadOnly in class EngineWrapper

Returns:

true if engine is read-only

canSnapshot

public boolean canSnapshot()

Specified by:

canSnapshot in interface Engine

Overrides:

canSnapshot in class EngineWrapper

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.

Specified by:

snapshot in interface Engine

Overrides:

snapshot in class EngineWrapper

Throws:

UnsupportedOperationException - if snapshots are not supported/enabled

See Also:

EngineWrapper.canSnapshot()