PersistentCollection (Hibernate API Documentation) - Hibernate 3.2.3 正式版 API 英文文档

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org.hibernate.collection
Interface PersistentCollection

All Known Implementing Classes:: AbstractPersistentCollection

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

public 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

public void setOwner(Object entity)

Set the reference to the owning entity

empty

public boolean empty()

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

setSnapshot

public void setSnapshot(Serializable key,
                        String role,
                        Serializable snapshot)

After flushing, re-init snapshot state.

postAction

public void postAction()

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

getValue

public Object getValue()

return the user-visible collection (or array) instance

beginRead

public void beginRead()

Called just before reading any rows from the JDBC result set

endRead

public boolean endRead()

Called after reading all rows from the JDBC result set

afterInitialize

public boolean afterInitialize()

Called after initializing from cache

isDirectlyAccessible

public boolean isDirectlyAccessible()

Could the application possibly have a direct reference to the underlying collection implementation?

unsetSession

public boolean unsetSession(SessionImplementor currentSession)

Disassociate this collection from the given session.

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

setCurrentSession

public 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

public void initializeFromCache(CollectionPersister persister,
                                Serializable disassembled,
                                Object owner)
                         throws HibernateException

Read the state of the collection from a disassembled cached value

Throws:: HibernateException

entries

public Iterator entries(CollectionPersister persister)

Iterate all collection entries, during update of the database

readFrom

public 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

public Object getIdentifier(Object entry,
                            int i)

Get the index of the given collection entry

getIndex

public 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

public Object getElement(Object entry)

Get the value of the given collection entry

getSnapshotElement

public Object getSnapshotElement(Object entry,
                                 int i)

Get the snapshot value of the given collection entry

beforeInitialize

public 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

public boolean equalsSnapshot(CollectionPersister persister)
                       throws HibernateException

Does the current state exactly match the snapshot?

Throws:: HibernateException

isSnapshotEmpty

public boolean isSnapshotEmpty(Serializable snapshot)

Is the snapshot empty?

disassemble

public Serializable disassemble(CollectionPersister persister)
                         throws HibernateException

Disassemble the collection, ready for the cache

Throws:: HibernateException

needsRecreate

public boolean needsRecreate(CollectionPersister persister)

Do we need to completely recreate this collection when it changes?

getSnapshot

public Serializable getSnapshot(CollectionPersister persister)
                         throws HibernateException

Return a new snapshot of the current state of the collection

Throws:: HibernateException

forceInitialization

public void forceInitialization()
                         throws HibernateException

To be called internally by the session, forcing immediate initialization.

Throws:: HibernateException

entryExists

public boolean entryExists(Object entry,
                           int i)

Does an element exist at this entry in the collection?

needsInserting

public boolean needsInserting(Object entry,
                              int i,
                              Type elemType)
                       throws HibernateException

Do we need to insert this element?

Throws:: HibernateException

needsUpdating

public boolean needsUpdating(Object entry,
                             int i,
                             Type elemType)
                      throws HibernateException

Do we need to update this element?

Throws:: HibernateException

isRowUpdatePossible

public boolean isRowUpdatePossible()

getDeletes

public Iterator getDeletes(CollectionPersister persister,
                           boolean indexIsFormula)
                    throws HibernateException

Get all the elements that need deleting

Throws:: HibernateException

isWrapper

public boolean isWrapper(Object collection)

Is this the wrapper for the given underlying collection instance?

wasInitialized

public boolean wasInitialized()

Is this instance initialized?

hasQueuedOperations

public boolean hasQueuedOperations()

Does this instance have any "queued" additions?

queuedAdditionIterator

public Iterator queuedAdditionIterator()

Iterate the "queued" additions

getQueuedOrphans

public Collection getQueuedOrphans(String entityName)

Get the "queued" orphans

getKey

public Serializable getKey()

Get the current collection key value

getRole

public String getRole()

Get the current role name

isUnreferenced

public boolean isUnreferenced()

Is the collection unreferenced?

isDirty

public 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

public void clearDirty()

Clear the dirty flag, after flushing changes to the database.

getStoredSnapshot

public Serializable getStoredSnapshot()

Get the snapshot cached by the collection instance

dirty

public void dirty()

Mark the collection as dirty

preInsert

public void preInsert(CollectionPersister persister)
               throws HibernateException

Called before inserting rows, to ensure that any surrogate keys are fully generated

Throws:: HibernateException

afterRowInsert

public void afterRowInsert(CollectionPersister persister,
                           Object entry,
                           int i)
                    throws HibernateException

Called after inserting a row, to fetch the natively generated id

Throws:: HibernateException

getOrphans

public Collection getOrphans(Serializable snapshot,
                             String entityName)
                      throws HibernateException

get all "orphaned" elements

Throws:: HibernateException