org.hibernate.collection
Interface PersistentCollection

All Known Implementing Classes:
AbstractPersistentCollection, PersistentArrayHolder, PersistentBag, PersistentElementHolder, PersistentIdentifierBag, PersistentIndexedElementHolder, PersistentList, PersistentListElementHolder, PersistentMap, PersistentMapElementHolder, PersistentSet, PersistentSortedMap, PersistentSortedSet

public interface PersistentCollection

Persistent collections are treated as value objects by Hibernate. ie. they have no independent existence beyond the object holding a reference to them. Unlike instances of entity classes, they are automatically deleted when unreferenced and automatically become persistent when held by a persistent object. Collections can be passed between different objects (change "roles") and this might cause their elements to move from one database table to another.

Hibernate "wraps" a java collection in an instance of PersistentCollection. This mechanism is designed to support tracking of changes to the collection's persistent state and lazy instantiation of collection elements. The downside is that only certain abstract collection types are supported and any extra semantics are lost

Applications should never use classes in this package directly, unless extending the "framework" here.

Changes to structure of the collection are recorded by the collection calling back to the session. Changes to mutable elements (ie. composite elements) are discovered by cloning their state when the collection is initialized and comparing at flush time.

Author:
Gavin King

Method Summary
 boolean afterInitialize()
          Called after initializing from cache
 void afterRowInsert(CollectionPersister persister, Object entry, int i)
          Called after inserting a row, to fetch the natively generated id
 void beforeInitialize(CollectionPersister persister, int anticipatedSize)
          Called before any elements are read into the collection, allowing appropriate initializations to occur.
 void beginRead()
          Called just before reading any rows from the JDBC result set
 void clearDirty()
          Clear the dirty flag, after flushing changes to the database.
 void dirty()
          Mark the collection as dirty
 Serializable disassemble(CollectionPersister persister)
          Disassemble the collection, ready for the cache
 boolean empty()
          Is the collection empty? (don't try to initialize the collection)
 boolean endRead()
          Called after reading all rows from the JDBC result set
 Iterator entries(CollectionPersister persister)
          Iterate all collection entries, during update of the database
 boolean entryExists(Object entry, int i)
          Does an element exist at this entry in the collection?
 boolean equalsSnapshot(CollectionPersister persister)
          Does the current state exactly match the snapshot?
 void forceInitialization()
          To be called internally by the session, forcing immediate initialization.
 Iterator getDeletes(CollectionPersister persister, boolean indexIsFormula)
          Get all the elements that need deleting
 Object getElement(Object entry)
          Get the value of the given collection entry
 Object getIdentifier(Object entry, int i)
          Get the index of the given collection entry
 Object getIndex(Object entry, int i, CollectionPersister persister)
          Get the index of the given collection entry
 Serializable getKey()
          Get the current collection key value
 Collection getOrphans(Serializable snapshot, String entityName)
          get all "orphaned" elements
 Object getOwner()
          Get the owning entity.
 Collection getQueuedOrphans(String entityName)
          Get the "queued" orphans
 String getRole()
          Get the current role name
 Serializable getSnapshot(CollectionPersister persister)
          Return a new snapshot of the current state of the collection
 Object getSnapshotElement(Object entry, int i)
          Get the snapshot value of the given collection entry
 Serializable getStoredSnapshot()
          Get the snapshot cached by the collection instance
 Object getValue()
          return the user-visible collection (or array) instance
 boolean hasQueuedOperations()
          Does this instance have any "queued" additions?
 void initializeFromCache(CollectionPersister persister, Serializable disassembled, Object owner)
          Read the state of the collection from a disassembled cached value
 boolean isDirectlyAccessible()
          Could the application possibly have a direct reference to the underlying collection implementation?
 boolean isDirty()
          Is the collection dirty? Note that this is only reliable during the flush cycle, after the collection elements are dirty checked against the snapshot.
 boolean isRowUpdatePossible()
           
 boolean isSnapshotEmpty(Serializable snapshot)
          Is the snapshot empty?
 boolean isUnreferenced()
          Is the collection unreferenced?
 boolean isWrapper(Object collection)
          Is this the wrapper for the given underlying collection instance?
 boolean needsInserting(Object entry, int i, Type elemType)
          Do we need to insert this element?
 boolean needsRecreate(CollectionPersister persister)
          Do we need to completely recreate this collection when it changes?
 boolean needsUpdating(Object entry, int i, Type elemType)
          Do we need to update this element?
 void postAction()
          After flushing, clear any "queued" additions, since the database state is now synchronized with the memory state.
 void preInsert(CollectionPersister persister)
          Called before inserting rows, to ensure that any surrogate keys are fully generated
 Iterator queuedAdditionIterator()
          Iterate the "queued" additions
 Object readFrom(ResultSet rs, CollectionPersister role, CollectionAliases descriptor, Object owner)
          Read a row from the JDBC result set
 boolean setCurrentSession(SessionImplementor session)
          Associate the collection with the given session.
 void setOwner(Object entity)
          Set the reference to the owning entity
 void setSnapshot(Serializable key, String role, Serializable snapshot)
          After flushing, re-init snapshot state.
 boolean unsetSession(SessionImplementor currentSession)
          Disassociate this collection from the given session.
 boolean wasInitialized()
          Is this instance initialized?
 

Method Detail

getOwner

Object getOwner()
Get the owning entity. Note that the owner is only set during the flush cycle, and when a new collection wrapper is created while loading an entity.


setOwner

void setOwner(Object entity)
Set the reference to the owning entity


empty

boolean empty()
Is the collection empty? (don't try to initialize the collection)


setSnapshot

void setSnapshot(Serializable key,
                 String role,
                 Serializable snapshot)
After flushing, re-init snapshot state.


postAction

void postAction()
After flushing, clear any "queued" additions, since the database state is now synchronized with the memory state.


getValue

Object getValue()
return the user-visible collection (or array) instance


beginRead

void beginRead()
Called just before reading any rows from the JDBC result set


endRead

boolean endRead()
Called after reading all rows from the JDBC result set


afterInitialize

boolean afterInitialize()
Called after initializing from cache


isDirectlyAccessible

boolean isDirectlyAccessible()
Could the application possibly have a direct reference to the underlying collection implementation?


unsetSession

boolean unsetSession(SessionImplementor currentSession)
Disassociate this collection from the given session.

Returns:
true if this was currently associated with the given session

setCurrentSession

boolean setCurrentSession(SessionImplementor session)
                          throws HibernateException
Associate the collection with the given session.

Returns:
false if the collection was already associated with the session
Throws:
HibernateException - if the collection was already associated with another open session

initializeFromCache

void initializeFromCache(CollectionPersister persister,
                         Serializable disassembled,
                         Object owner)
                         throws HibernateException
Read the state of the collection from a disassembled cached value

Throws:
HibernateException

entries

Iterator entries(CollectionPersister persister)
Iterate all collection entries, during update of the database


readFrom

Object readFrom(ResultSet rs,
                CollectionPersister role,
                CollectionAliases descriptor,
                Object owner)
                throws HibernateException,
                       SQLException
Read a row from the JDBC result set

Throws:
HibernateException
SQLException

getIdentifier

Object getIdentifier(Object entry,
                     int i)
Get the index of the given collection entry


getIndex

Object getIndex(Object entry,
                int i,
                CollectionPersister persister)
Get the index of the given collection entry

Parameters:
persister - it was more elegant before we added this...

getElement

Object getElement(Object entry)
Get the value of the given collection entry


getSnapshotElement

Object getSnapshotElement(Object entry,
                          int i)
Get the snapshot value of the given collection entry


beforeInitialize

void beforeInitialize(CollectionPersister persister,
                      int anticipatedSize)
Called before any elements are read into the collection, allowing appropriate initializations to occur.

Parameters:
persister - The underlying collection persister.
anticipatedSize - The anticipated size of the collection after initilization is complete.

equalsSnapshot

boolean equalsSnapshot(CollectionPersister persister)
                       throws HibernateException
Does the current state exactly match the snapshot?

Throws:
HibernateException

isSnapshotEmpty

boolean isSnapshotEmpty(Serializable snapshot)
Is the snapshot empty?


disassemble

Serializable disassemble(CollectionPersister persister)
                         throws HibernateException
Disassemble the collection, ready for the cache

Throws:
HibernateException

needsRecreate

boolean needsRecreate(CollectionPersister persister)
Do we need to completely recreate this collection when it changes?


getSnapshot

Serializable getSnapshot(CollectionPersister persister)
                         throws HibernateException
Return a new snapshot of the current state of the collection

Throws:
HibernateException

forceInitialization

void forceInitialization()
                         throws HibernateException
To be called internally by the session, forcing immediate initialization.

Throws:
HibernateException

entryExists

boolean entryExists(Object entry,
                    int i)
Does an element exist at this entry in the collection?


needsInserting

boolean needsInserting(Object entry,
                       int i,
                       Type elemType)
                       throws HibernateException
Do we need to insert this element?

Throws:
HibernateException

needsUpdating

boolean needsUpdating(Object entry,
                      int i,
                      Type elemType)
                      throws HibernateException
Do we need to update this element?

Throws:
HibernateException

isRowUpdatePossible

boolean isRowUpdatePossible()

getDeletes

Iterator getDeletes(CollectionPersister persister,
                    boolean indexIsFormula)
                    throws HibernateException
Get all the elements that need deleting

Throws:
HibernateException

isWrapper

boolean isWrapper(Object collection)
Is this the wrapper for the given underlying collection instance?


wasInitialized

boolean wasInitialized()
Is this instance initialized?


hasQueuedOperations

boolean hasQueuedOperations()
Does this instance have any "queued" additions?


queuedAdditionIterator

Iterator queuedAdditionIterator()
Iterate the "queued" additions


getQueuedOrphans

Collection getQueuedOrphans(String entityName)
Get the "queued" orphans


getKey

Serializable getKey()
Get the current collection key value


getRole

String getRole()
Get the current role name


isUnreferenced

boolean isUnreferenced()
Is the collection unreferenced?


isDirty

boolean isDirty()
Is the collection dirty? Note that this is only reliable during the flush cycle, after the collection elements are dirty checked against the snapshot.


clearDirty

void clearDirty()
Clear the dirty flag, after flushing changes to the database.


getStoredSnapshot

Serializable getStoredSnapshot()
Get the snapshot cached by the collection instance


dirty

void dirty()
Mark the collection as dirty


preInsert

void preInsert(CollectionPersister persister)
               throws HibernateException
Called before inserting rows, to ensure that any surrogate keys are fully generated

Throws:
HibernateException

afterRowInsert

void afterRowInsert(CollectionPersister persister,
                    Object entry,
                    int i)
                    throws HibernateException
Called after inserting a row, to fetch the natively generated id

Throws:
HibernateException

getOrphans

Collection getOrphans(Serializable snapshot,
                      String entityName)
                      throws HibernateException
get all "orphaned" elements

Throws:
HibernateException


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