org.hydrateframework.event
Class ObjectAccessEventHandler.LazyCollectionEventHandler

java.lang.Object
  org.hydrateframework.event.ObjectAccessEventHandler.LazyLoadAccessEventHandler
      org.hydrateframework.event.ObjectAccessEventHandler.LazyCollectionEventHandler

All Implemented Interfaces:

ObjectAccessEventHandler

Enclosing interface:

ObjectAccessEventHandler

public abstract static class ObjectAccessEventHandler.LazyCollectionEventHandler
extends ObjectAccessEventHandler.LazyLoadAccessEventHandler

Nested Class Summary

Nested classes/interfaces inherited from interface org.hydrateframework.event.ObjectAccessEventHandler

ObjectAccessEventHandler.EmptyAccessEventHandler, ObjectAccessEventHandler.LazyCollectionEventHandler, ObjectAccessEventHandler.LazyLoadAccessEventHandler, ObjectAccessEventHandler.WaitForPopulationEventHandler

Field Summary

protected static java.util.Map<HydrateObject,java.util.Map<java.lang.String,java.util.Collection>>	m_collections
protected java.lang.String	m_dsName
protected java.lang.String[]	m_forAttributes

Fields inherited from class org.hydrateframework.event.ObjectAccessEventHandler.LazyLoadAccessEventHandler

m_log

Constructor Summary

protected

ObjectAccessEventHandler.LazyCollectionEventHandler(java.lang.String dsName, java.lang.String[] forAttributes)

Method Summary

protected static java.util.Collection	getCollection(HydrateObject obj, java.lang.String attr, java.lang.Class collClass)
java.util.Collection	getWeakCollection(HydrateObject obj, java.lang.String attr, java.lang.Class collClass) This method is needed to resolve the obscure, but tricky relationship between autoload references and lazy loading.

Methods inherited from class org.hydrateframework.event.ObjectAccessEventHandler.LazyLoadAccessEventHandler

attributeNotLoaded, collectionNotLoaded

Methods inherited from class java.lang.Object

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

Field Detail

m_dsName

protected java.lang.String m_dsName

m_forAttributes

protected java.lang.String[] m_forAttributes

m_collections

protected static java.util.Map<HydrateObject,java.util.Map<java.lang.String,java.util.Collection>> m_collections

Constructor Detail

ObjectAccessEventHandler.LazyCollectionEventHandler

protected ObjectAccessEventHandler.LazyCollectionEventHandler(java.lang.String dsName,
                                                              java.lang.String[] forAttributes)

Method Detail

getWeakCollection

public java.util.Collection getWeakCollection(HydrateObject obj,
                                              java.lang.String attr,
                                              java.lang.Class collClass)

Description copied from interface: ObjectAccessEventHandler

This method is needed to resolve the obscure, but tricky relationship between autoload references and lazy loading. Our problem is that on loading objects we often implicitly fix up back references to unloaded collections. However, this gets in the way of the lazy loading of collections because either the collection will try and load when the back reference is created, or it will block subsequent implicit loading of the full collection afterwards. The solution is to permit weakly referenced collections that are not part of the class until explicity created but can keep track of these back references in the meantime. This method requests the creation (or resolution) of such a weakly referenced collection. These collections should always disappear as soon as the object they belong to is eligible for garbage collection

Specified by:

getWeakCollection in interface ObjectAccessEventHandler

Overrides:

getWeakCollection in class ObjectAccessEventHandler.LazyLoadAccessEventHandler

Parameters:

obj - the hydrate object that needs a collection. Don't even start thinking about getting this to work with non-Hydrate objects.

attr - the name of the attribute (must be the static reference from the interface)

collClass - the class of the collection that would be created if there is none available.

Returns:

this method should return null if it doesn't implement collectionNotLoaded i.e. doesn't concern itself with lazy loading of collections. If it does, it must return a collection that 'belongs' to the given object. In other words, subsequent calls to this method must return the same collection, but that collection must be eligible for garbage collection when the object reference goes out of scope.

getCollection

protected static java.util.Collection getCollection(HydrateObject obj,
                                                    java.lang.String attr,
                                                    java.lang.Class collClass)