org.mapdb

Class EngineWrapper.ImmutabilityCheckEngine

java.lang.Object

org.mapdb.EngineWrapper

org.mapdb.EngineWrapper.ImmutabilityCheckEngine

All Implemented Interfaces:

Engine

Enclosing class:

EngineWrapper

public static class EngineWrapper.ImmutabilityCheckEngine
extends EngineWrapper

check if Record Instances were not modified while in cache. Usuful to diagnose strange problems with Instance Cache.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	EngineWrapper.ImmutabilityCheckEngine.Item

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

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

Field Summary

Fields

Modifier and Type	Field and Description
protected LongConcurrentHashMap<EngineWrapper.ImmutabilityCheckEngine.Item>	items

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

Constructors

Modifier	Constructor and Description
protected	ImmutabilityCheckEngine(Engine engine)

Method Summary

Modifier and Type	Method and Description
void	close() Close store/cache.
<A> boolean	compareAndSwap(long recid, A expectedOldValue, A newValue, Serializer<A> serializer) Updates existing record in atomic (Compare And Swap) manner.
<A> A	get(long recid, Serializer<A> serializer) Get existing record.
<A> long	put(A value, Serializer<A> serializer) Insert new record.
<A> void	update(long recid, A value, Serializer<A> serializer) Update existing record with new value.

Methods inherited from class org.mapdb.EngineWrapper

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

Methods inherited from class java.lang.Object

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

Field Detail

items

protected LongConcurrentHashMap<EngineWrapper.ImmutabilityCheckEngine.Item> items

Constructor Detail

ImmutabilityCheckEngine

protected ImmutabilityCheckEngine(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'

Specified by:

get in interface Engine

Overrides:

get in class EngineWrapper

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.

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

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

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.closeOnJvmShutdown() which uses shutdown hook to automatically close Engine when JVM shutdowns.

Specified by:

close in interface Engine

Overrides:

close in class EngineWrapper