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