org.mapdb
Class Caches.HardRef

java.lang.Object
  org.mapdb.EngineWrapper
      org.mapdb.Caches.LRU
          org.mapdb.Caches.HardRef

All Implemented Interfaces:

Engine

Enclosing class:

Caches

public static class Caches.HardRef
extends Caches.LRU

Cache created objects using hard reference. It checks free memory every N operations (1024*10). If free memory is bellow 75% it clears the cache

Author:

Jan Kotek

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.Caches.LRU

cache, locks

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

Caches.HardRef(Engine engine, int initialCapacity, boolean disableLocks)

Method Summary

<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.
<A> A	get(long recid, Serializer<A> serializer) Get existing record.
<A> void	update(long recid, A value, Serializer<A> serializer) Update existing record with new value.

Methods inherited from class org.mapdb.Caches.LRU

clearCache, close, put, rollback

Methods inherited from class org.mapdb.EngineWrapper

canRollback, canSnapshot, checkClosed, closeListenerRegister, closeListenerUnregister, commit, compact, getSerializerPojo, getWrappedEngine, isClosed, isReadOnly, preallocate, preallocate, snapshot

Methods inherited from class java.lang.Object

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

Constructor Detail

Caches.HardRef

public Caches.HardRef(Engine engine,
                      int initialCapacity,
                      boolean disableLocks)

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'

Specified by:

get in interface Engine

Overrides:

get in class Caches.LRU

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.

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 Caches.LRU

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 Caches.LRU

Parameters:

recid - (record identifier) under which was record persisted

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

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 Caches.LRU

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