eu.fbk.knowledgestore.datastore

Class ForwardingDataStore

java.lang.Object

com.google.common.collect.ForwardingObject

eu.fbk.knowledgestore.datastore.ForwardingDataStore

All Implemented Interfaces:

DataStore, Component, Closeable, AutoCloseable

Direct Known Subclasses:

CachingDataStore, LoggingDataStore, SynchronizedDataStore

public abstract class ForwardingDataStore
extends ForwardingObject
implements DataStore

A DataStore forwarding all its method calls to another DataStore.

This class provides a starting point for implementing the decorator pattern on top of the DataStore interface. Subclasses must implement method delegate() and override the methods of DataStore they want to decorate.

Field Summary

Fields inherited from interface eu.fbk.knowledgestore.datastore.DataStore

SUPPORTED_TYPES

Constructor Summary

Constructors

Constructor and Description
ForwardingDataStore()

Method Summary

Modifier and Type	Method and Description
DataTransaction	begin(boolean readOnly) Begins a new read-only / read-write DataStore transaction.
void	close() Closes this Component object.
protected abstract DataStore	delegate()
void	init() Initializes the Component with the supplied Runtime object.

Methods inherited from class com.google.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

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

Constructor Detail

ForwardingDataStore

public ForwardingDataStore()

Method Detail

delegate

protected abstract DataStore delegate()

Specified by:

delegate in class ForwardingObject

init

public void init()
          throws IOException

Description copied from interface: Component

Initializes the Component with the supplied Runtime object. This method is called after the instantiation of a Component and before any other instance method is called. It provides a Runtime that can be used to access runtime services such as locking, serialization and filesystem access. The Component is allowed to perform any initialization operation that is necessary in order to become functional; on failure, these operations may result in a IOException being thrown.

Specified by:

init in interface Component

Throws:

IOException - in case initialization fails

begin

public DataTransaction begin(boolean readOnly)
                      throws IOException,
                             IllegalStateException

Description copied from interface: DataStore

Begins a new read-only / read-write DataStore transaction. All the accesses to a DataStore must occur in the scope of a transaction, that must be ended (possibly committing the modifications done) as soon as possible to allow improving throughput.

Specified by:

begin in interface DataStore

Parameters:

readOnly - true if the transaction is not allowed to modify the contents of the DataStore (this allows for optimizing accesses).

Returns:

the created transaction

Throws:

DataCorruptedException - in case a transaction cannot be started due to the DataStore persistent data being damaged or non-existing (this may trigger some external recovery procedure)

IOException - if another IO error occurs while starting the transaction

IllegalStateException - if the DataStore object has been already closed

close

public void close()

Description copied from interface: Component

Closes this Component object. If the component has been initialized, closing a it causes any allocated resource to be freed and any operation or transaction ongoing within the component being aborted; in case the component has not been initialized yet, or close() has already being called, calling this method has no effect. Note that the operation affects only the local Component object and not any remote service this object may rely on to implement its functionalities; in particular, such a remote service is not shutdown by the operation, so that it can be accessed by other Component instances possibly running in other (virtual) machines. Similarly, closing a Component object has no impact on stored data, that continues to be persisted and will be accessed unchanged (provided no external modification occurs) the next time a similarly configured Component is created.

Specified by:

close in interface Component

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable