org.entityfs.util
Class AggregatingEntityRepository

java.lang.Object
  org.entityfs.util.AggregatingEntityRepository

All Implemented Interfaces:

Iterable<EntityView>, EntityHolder, EntityListable, EntityRepository, Lockable, ReadLockable

public class AggregatingEntityRepository
extends Object
implements EntityRepository

This is an EntityRepository that aggregates the contents of several entity repositories. It can be used to make several directories look as one.

This object keeps an internal list of all repositories supplied to the constructor. When the client requests an entity, all repositories in the list are searched until the entity is found.

The read lock of this object is a CompoundEntityLock over all aggregated repositories. This object does not have any write lock since it is read only.

Since:

1.0

Author:

Karl Gustafsson

Constructor Summary

AggregatingEntityRepository(Collection<? extends EntityRepository> c)
Create a new object.

Method Summary

boolean	containsEntity(EntityView ev) Does this entity holder contain the supplied entity? If this is called on a symbolic link, it is checked if the link target is a directory and that directory contains the entity.
boolean	containsEntity(String name) Can an entity with the given name be retrieved from this object? If this is called on a symbolic link, it is checked if the link target is a directory and that directory contains an entity with the given name.
EntityView	getEntityOrNull(String name) Get the named entity.
EntityLock	getReadLock() Get the read lock without locking it.
boolean	isEmpty() Is the listable empty? If a directory view is empty, the viewed directory may still contain entities that are hidden by the view's filter.
boolean	isReadLockedByCurrentThread() Does the calling thread hold a read lock for this object? A write lock also qualifies as a read lock.
Iterator<EntityView>	iterator()
Set<EntityView>	listEntities() Return all entities that are visible in this directory.
EntityLock	lockForReading() Lock object for reading and return the lock.

Methods inherited from class java.lang.Object

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

Constructor Detail

AggregatingEntityRepository

public AggregatingEntityRepository(Collection<? extends EntityRepository> c)

Create a new object.

Parameters:

c - A collection of repositories. The repositories are added to the internal list of repositories in the order that they are returned when iterating over the collection.

Method Detail

getReadLock

public EntityLock getReadLock()

Description copied from interface: ReadLockable

Get the read lock without locking it.

This method always returns a lock, even if the object's file system is not locking or if the object is read only.

Specified by:

getReadLock in interface ReadLockable

Returns:

The lockable's read lock. This might be unlocked or locked by someone else.

lockForReading

public EntityLock lockForReading()

Description copied from interface: ReadLockable

Lock object for reading and return the lock. How the lock is acquired is determined by the EntityLockAdapterFactory and LockAcquiringStrategy used. If this is called on an object that somehow is connected to an entity object, that entity's file system's entity lock adapter factory and lock acquiring strategy is used.

A read lock cannot be upgraded to a write lock (just like how Java's ReadWriteLock works).

For more discussions on locks and locking, see Entity and FileSystem.

This method always returns a lock, even if the object's file system is not locking or if the object is read only.

Specified by:

lockForReading in interface ReadLockable

Returns:

A locked read lock.

isReadLockedByCurrentThread

public boolean isReadLockedByCurrentThread()

Description copied from interface: ReadLockable

Does the calling thread hold a read lock for this object? A write lock also qualifies as a read lock.

Specified by:

isReadLockedByCurrentThread in interface ReadLockable

Returns:

true if the lockable object is read or write locked by the current thread.

isEmpty

public boolean isEmpty()

Description copied from interface: EntityListable

Is the listable empty? If a directory view is empty, the viewed directory may still contain entities that are hidden by the view's filter.

Specified by:

isEmpty in interface EntityListable

Returns:

true if the directory view is empty.

containsEntity

public boolean containsEntity(String name)

Description copied from interface: EntityHolder

Can an entity with the given name be retrieved from this object? If this is called on a symbolic link, it is checked if the link target is a directory and that directory contains an entity with the given name.

Specified by:

containsEntity in interface EntityHolder

Parameters:

name - The name of the entity.

Returns:

true if there is an entity with the given name referenced by this holder.

containsEntity

public boolean containsEntity(EntityView ev)

Description copied from interface: EntityHolder

Does this entity holder contain the supplied entity? If this is called on a symbolic link, it is checked if the link target is a directory and that directory contains the entity.

Specified by:

containsEntity in interface EntityHolder

Parameters:

ev - The entity (or a view of it).

Returns:

true If the entity holder contains the supplied entity.

listEntities

public Set<EntityView> listEntities()

Description copied from interface: EntityListable

Return all entities that are visible in this directory. The result is not sorted in any way.

If this is called on a directory view, all returned ViewCapable entities inherit the view's filters.

Specified by:

listEntities in interface EntityListable

Returns:

A Set of entity views. If this is called on a directory entity object, a set of entity objects (not views) are returned. The set may be empty, but never null.

getEntityOrNull

public EntityView getEntityOrNull(String name)

Description copied from interface: EntityHolder

Get the named entity. For directories, this is an entity in the directory. For a symbolic link pointing to a directory, this is an entity in the target directory.

If this is called on a directory view, and the returned entity is ViewCapable, the returned entity view inherits the same view settings as the directory view (same filter instances).

If this is called on an EntityHolder that contains several entities with the same name, the implementation may choose how to deal with that. This can never happen for directories since entity names in a directory are required to be unique.

Specified by:

getEntityOrNull in interface EntityHolder

Parameters:

name - The name of the entity.

Returns:

An EntityView or null. If this method is called on a DirectoryView and the returned entity is ViewCapable , the returned object inherits the view settings of the parent. If the returned entity is a file, the returned object can be cast to an EFile, if it is a directory, it can be cast to a DirectoryView (or a Directory if this method is called on a Directory rather than a DirectoryView). The type of the returned object can be determined by calling its EntityView.getType() method or by using instanceof.

iterator

public Iterator<EntityView> iterator()

Specified by:

iterator in interface Iterable<EntityView>