//$Id: DefaultLoadEventListener.java 14127 2007-10-20 00:06:51Z scottmarlownovell $
package org.hibernate.event.def;
import java.io.Serializable;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.NonUniqueObjectException;
import org.hibernate.PersistentObjectException;
import org.hibernate.TypeMismatchException;
import org.hibernate.EntityMode;
import org.hibernate.cache.CacheConcurrencyStrategy;
import org.hibernate.cache.CacheKey;
import org.hibernate.cache.entry.CacheEntry;
import org.hibernate.engine.EntityEntry;
import org.hibernate.engine.EntityKey;
import org.hibernate.engine.PersistenceContext;
import org.hibernate.engine.SessionFactoryImplementor;
import org.hibernate.engine.SessionImplementor;
import org.hibernate.engine.Status;
import org.hibernate.engine.TwoPhaseLoad;
import org.hibernate.engine.Versioning;
import org.hibernate.event.EventSource;
import org.hibernate.event.LoadEvent;
import org.hibernate.event.LoadEventListener;
import org.hibernate.event.PostLoadEvent;
import org.hibernate.event.PostLoadEventListener;
import org.hibernate.persister.entity.EntityPersister;
import org.hibernate.pretty.MessageHelper;
import org.hibernate.proxy.HibernateProxy;
import org.hibernate.proxy.LazyInitializer;
import org.hibernate.type.Type;
import org.hibernate.type.TypeFactory;
/**
* Defines the default load event listeners used by hibernate for loading entities
* in response to generated load events.
*
* @author Steve Ebersole
*/
public class DefaultLoadEventListener extends AbstractLockUpgradeEventListener implements LoadEventListener {
public static final Object REMOVED_ENTITY_MARKER = new Object();
public static final Object INCONSISTENT_RTN_CLASS_MARKER = new Object();
public static final LockMode DEFAULT_LOCK_MODE = LockMode.NONE;
private static final Log log = LogFactory.getLog(DefaultLoadEventListener.class);
/**
* Handle the given load event.
*
* @param event The load event to be handled.
* @throws HibernateException
*/
public void onLoad(LoadEvent event, LoadEventListener.LoadType loadType) throws HibernateException {
final SessionImplementor source = event.getSession();
EntityPersister persister;
if ( event.getInstanceToLoad() != null ) {
persister = source.getEntityPersister( null, event.getInstanceToLoad() ); //the load() which takes an entity does not pass an entityName
event.setEntityClassName( event.getInstanceToLoad().getClass().getName() );
}
else {
persister = source.getFactory().getEntityPersister( event.getEntityClassName() );
}
if ( persister == null ) {
throw new HibernateException(
"Unable to locate persister: " +
event.getEntityClassName()
);
}
if ( persister.getIdentifierType().isComponentType() && EntityMode.DOM4J == event.getSession().getEntityMode() ) {
// skip this check for composite-ids relating to dom4j entity-mode;
// alternatively, we could add a check to make sure the incoming id value is
// an instance of Element...
}
else {
Class idClass = persister.getIdentifierType().getReturnedClass();
if ( idClass != null && ! idClass.isInstance( event.getEntityId() ) ) {
throw new TypeMismatchException(
"Provided id of the wrong type. Expected: " + idClass + ", got " + event.getEntityId().getClass()
);
}
}
EntityKey keyToLoad = new EntityKey( event.getEntityId(), persister, source.getEntityMode() );
try {
if ( loadType.isNakedEntityReturned() ) {
//do not return a proxy!
//(this option indicates we are initializing a proxy)
event.setResult( load(event, persister, keyToLoad, loadType) );
}
else {
//return a proxy if appropriate
if ( event.getLockMode() == LockMode.NONE ) {
event.setResult( proxyOrLoad(event, persister, keyToLoad, loadType) );
}
else {
event.setResult( lockAndLoad(event, persister, keyToLoad, loadType, source) );
}
}
}
catch(HibernateException e) {
log.info("Error performing load command", e);
throw e;
}
}
/**
* Perfoms the load of an entity.
*
* @return The loaded entity.
* @throws HibernateException
*/
protected Object load(
final LoadEvent event,
final EntityPersister persister,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options)
throws HibernateException {
if ( event.getInstanceToLoad() != null ) {
if ( event.getSession().getPersistenceContext().getEntry( event.getInstanceToLoad() ) != null ) {
throw new PersistentObjectException(
"attempted to load into an instance that was already associated with the session: " +
MessageHelper.infoString( persister, event.getEntityId(), event.getSession().getFactory() )
);
}
persister.setIdentifier( event.getInstanceToLoad(), event.getEntityId(), event.getSession().getEntityMode() );
}
Object entity = doLoad(event, persister, keyToLoad, options);
boolean isOptionalInstance = event.getInstanceToLoad() != null;
if ( !options.isAllowNulls() || isOptionalInstance ) {
if ( entity == null ) {
event.getSession().getFactory().getEntityNotFoundDelegate().handleEntityNotFound( event.getEntityClassName(), event.getEntityId() );
}
}
if ( isOptionalInstance && entity != event.getInstanceToLoad() ) {
throw new NonUniqueObjectException( event.getEntityId(), event.getEntityClassName() );
}
return entity;
}
/**
* Based on configured options, will either return a pre-existing proxy,
* generate a new proxy, or perform an actual load.
*
* @return The result of the proxy/load operation.
* @throws HibernateException
*/
protected Object proxyOrLoad(
final LoadEvent event,
final EntityPersister persister,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options)
throws HibernateException {
if ( log.isTraceEnabled() ) {
log.trace(
"loading entity: " +
MessageHelper.infoString( persister, event.getEntityId(), event.getSession().getFactory() )
);
}
if ( !persister.hasProxy() ) {
// this class has no proxies (so do a shortcut)
return load(event, persister, keyToLoad, options);
}
else {
final PersistenceContext persistenceContext = event.getSession().getPersistenceContext();
// look for a proxy
Object proxy = persistenceContext.getProxy(keyToLoad);
if ( proxy != null ) {
return returnNarrowedProxy( event, persister, keyToLoad, options, persistenceContext, proxy );
}
else {
if ( options.isAllowProxyCreation() ) {
return createProxyIfNecessary( event, persister, keyToLoad, options, persistenceContext );
}
else {
// return a newly loaded object
return load(event, persister, keyToLoad, options);
}
}
}
}
/**
* Given that there is a pre-existing proxy.
* Initialize it if necessary; narrow if necessary.
*/
private Object returnNarrowedProxy(
final LoadEvent event,
final EntityPersister persister,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options,
final PersistenceContext persistenceContext,
final Object proxy
) {
log.trace("entity proxy found in session cache");
LazyInitializer li = ( (HibernateProxy) proxy ).getHibernateLazyInitializer();
if ( li.isUnwrap() ) {
return li.getImplementation();
}
Object impl = null;
if ( !options.isAllowProxyCreation() ) {
impl = load( event, persister, keyToLoad, options );
if ( impl == null ) {
event.getSession().getFactory().getEntityNotFoundDelegate().handleEntityNotFound( persister.getEntityName(), keyToLoad.getIdentifier());
}
}
return persistenceContext.narrowProxy( proxy, persister, keyToLoad, impl );
}
/**
* Given that there is no pre-existing proxy.
* Check if the entity is already loaded. If it is, return the entity,
* otherwise create and return a proxy.
*/
private Object createProxyIfNecessary(
final LoadEvent event,
final EntityPersister persister,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options,
final PersistenceContext persistenceContext
) {
Object existing = persistenceContext.getEntity( keyToLoad );
if ( existing != null ) {
// return existing object or initialized proxy (unless deleted)
log.trace( "entity found in session cache" );
if ( options.isCheckDeleted() ) {
EntityEntry entry = persistenceContext.getEntry( existing );
Status status = entry.getStatus();
if ( status == Status.DELETED || status == Status.GONE ) {
return null;
}
}
return existing;
}
else {
log.trace( "creating new proxy for entity" );
// return new uninitialized proxy
Object proxy = persister.createProxy( event.getEntityId(), event.getSession() );
persistenceContext.getBatchFetchQueue().addBatchLoadableEntityKey(keyToLoad);
persistenceContext.addProxy(keyToLoad, proxy);
return proxy;
}
}
/**
* If the class to be loaded has been configured with a cache, then lock
* given id in that cache and then perform the load.
*
* @return The loaded entity
* @throws HibernateException
*/
protected Object lockAndLoad(
final LoadEvent event,
final EntityPersister persister,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options,
final SessionImplementor source)
throws HibernateException {
CacheConcurrencyStrategy.SoftLock lock = null;
final CacheKey ck;
if ( persister.hasCache() ) {
ck = new CacheKey(
event.getEntityId(),
persister.getIdentifierType(),
persister.getRootEntityName(),
source.getEntityMode(),
source.getFactory()
);
lock = persister.getCache().lock(ck, null );
}
else {
ck = null;
}
Object entity;
try {
entity = load(event, persister, keyToLoad, options);
}
finally {
if ( persister.hasCache() ) {
persister.getCache().release(ck, lock );
}
}
Object proxy = event.getSession().getPersistenceContext()
.proxyFor( persister, keyToLoad, entity );
return proxy;
}
/**
* Coordinates the efforts to load a given entity. First, an attempt is
* made to load the entity from the session-level cache. If not found there,
* an attempt is made to locate it in second-level cache. Lastly, an
* attempt is made to load it directly from the datasource.
*
* @param event The load event
* @param persister The persister for the entity being requested for load
* @param keyToLoad The EntityKey representing the entity to be loaded.
* @param options The load options.
* @return The loaded entity, or null.
* @throws HibernateException
*/
protected Object doLoad(
final LoadEvent event,
final EntityPersister persister,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options) throws HibernateException {
if ( log.isTraceEnabled() ) {
log.trace(
"attempting to resolve: " +
MessageHelper.infoString( persister, event.getEntityId(), event.getSession().getFactory() )
);
}
Object entity = loadFromSessionCache( event, keyToLoad, options );
if ( entity == REMOVED_ENTITY_MARKER ) {
log.debug( "load request found matching entity in context, but it is scheduled for removal; returning null" );
return null;
}
if ( entity == INCONSISTENT_RTN_CLASS_MARKER ) {
log.debug( "load request found matching entity in context, but the matched entity was of an inconsistent return type; returning null" );
return null;
}
if ( entity != null ) {
if ( log.isTraceEnabled() ) {
log.trace(
"resolved object in session cache: " +
MessageHelper.infoString( persister, event.getEntityId(), event.getSession().getFactory() )
);
}
return entity;
}
entity = loadFromSecondLevelCache(event, persister, options);
if ( entity != null ) {
if ( log.isTraceEnabled() ) {
log.trace(
"resolved object in second-level cache: " +
MessageHelper.infoString( persister, event.getEntityId(), event.getSession().getFactory() )
);
}
return entity;
}
if ( log.isTraceEnabled() ) {
log.trace(
"object not resolved in any cache: " +
MessageHelper.infoString( persister, event.getEntityId(), event.getSession().getFactory() )
);
}
return loadFromDatasource(event, persister, keyToLoad, options);
}
/**
* Performs the process of loading an entity from the configured
* underlying datasource.
*
* @param event The load event
* @param persister The persister for the entity being requested for load
* @param keyToLoad The EntityKey representing the entity to be loaded.
* @param options The load options.
* @return The object loaded from the datasource, or null if not found.
* @throws HibernateException
*/
protected Object loadFromDatasource(
final LoadEvent event,
final EntityPersister persister,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options) throws HibernateException {
final SessionImplementor source = event.getSession();
final boolean stats = source.getFactory().getStatistics().isStatisticsEnabled();
long startTime = 0;
if ( stats ) startTime = System.currentTimeMillis();
Object entity = persister.load(
event.getEntityId(),
event.getInstanceToLoad(),
event.getLockMode(),
source
);
if ( event.isAssociationFetch() && stats) {
source.getFactory().getStatisticsImplementor().fetchEntity( event.getEntityClassName(), System.currentTimeMillis() - startTime);
}
return entity;
}
/**
* Attempts to locate the entity in the session-level cache.
* <p/>
* If allowed to return nulls, then if the entity happens to be found in
* the session cache, we check the entity type for proper handling
* of entity hierarchies.
* <p/>
* If checkDeleted was set to true, then if the entity is found in the
* session-level cache, it's current status within the session cache
* is checked to see if it has previously been scheduled for deletion.
*
* @param event The load event
* @param keyToLoad The EntityKey representing the entity to be loaded.
* @param options The load options.
* @return The entity from the session-level cache, or null.
* @throws HibernateException Generally indicates problems applying a lock-mode.
*/
protected Object loadFromSessionCache(
final LoadEvent event,
final EntityKey keyToLoad,
final LoadEventListener.LoadType options) throws HibernateException {
SessionImplementor session = event.getSession();
Object old = session.getEntityUsingInterceptor( keyToLoad );
if ( old != null ) {
// this object was already loaded
EntityEntry oldEntry = session.getPersistenceContext().getEntry( old );
if ( options.isCheckDeleted() ) {
Status status = oldEntry.getStatus();
if ( status == Status.DELETED || status == Status.GONE ) {
return REMOVED_ENTITY_MARKER;
}
}
if ( options.isAllowNulls() ) {
EntityPersister persister = event.getSession().getFactory().getEntityPersister( event.getEntityClassName() );
if ( ! persister.isInstance( old, event.getSession().getEntityMode() ) ) {
return INCONSISTENT_RTN_CLASS_MARKER;
}
}
upgradeLock( old, oldEntry, event.getLockMode(), session );
}
return old;
}
/**
* Attempts to load the entity from the second-level cache.
*
* @param event The load event
* @param persister The persister for the entity being requested for load
* @param options The load options.
* @return The entity from the second-level cache, or null.
* @throws HibernateException
*/
protected Object loadFromSecondLevelCache(
final LoadEvent event,
final EntityPersister persister,
final LoadEventListener.LoadType options) throws HibernateException {
final SessionImplementor source = event.getSession();
final boolean useCache = persister.hasCache() &&
source.getCacheMode().isGetEnabled() &&
event.getLockMode().lessThan(LockMode.READ);
if (useCache) {
final SessionFactoryImplementor factory = source.getFactory();
final CacheKey ck = new CacheKey(
event.getEntityId(),
persister.getIdentifierType(),
persister.getRootEntityName(),
source.getEntityMode(),
source.getFactory()
);
Object ce = persister.getCache()
.get( ck, source.getTimestamp() );
if ( factory.getStatistics().isStatisticsEnabled() ) {
if (ce==null) {
factory.getStatisticsImplementor().secondLevelCacheMiss(
persister.getCache().getRegionName()
);
}
else {
factory.getStatisticsImplementor().secondLevelCacheHit(
persister.getCache().getRegionName()
);
}
}
if ( ce != null ) {
CacheEntry entry = (CacheEntry) persister.getCacheEntryStructure()
.destructure(ce, factory);
// Entity was found in second-level cache...
return assembleCacheEntry(
entry,
event.getEntityId(),
persister,
event
);
}
}
return null;
}
private Object assembleCacheEntry(
final CacheEntry entry,
final Serializable id,
final EntityPersister persister,
final LoadEvent event) throws HibernateException {
final Object optionalObject = event.getInstanceToLoad();
final EventSource session = event.getSession();
final SessionFactoryImplementor factory = session.getFactory();
if ( log.isTraceEnabled() ) {
log.trace(
"assembling entity from second-level cache: " +
MessageHelper.infoString( persister, id, factory )
);
}
EntityPersister subclassPersister = factory.getEntityPersister( entry.getSubclass() );
Object result = optionalObject == null ?
session.instantiate( subclassPersister, id ) : optionalObject;
// make it circular-reference safe
TwoPhaseLoad.addUninitializedCachedEntity(
new EntityKey( id, subclassPersister, session.getEntityMode() ),
result,
subclassPersister,
LockMode.NONE,
entry.areLazyPropertiesUnfetched(),
entry.getVersion(),
session
);
Type[] types = subclassPersister.getPropertyTypes();
Object[] values = entry.assemble( result, id, subclassPersister, session.getInterceptor(), session ); // intializes result by side-effect
TypeFactory.deepCopy(
values,
types,
subclassPersister.getPropertyUpdateability(),
values,
session
);
Object version = Versioning.getVersion( values, subclassPersister );
if ( log.isTraceEnabled() ) log.trace( "Cached Version: " + version );
final PersistenceContext persistenceContext = session.getPersistenceContext();
persistenceContext.addEntry(
result,
Status.MANAGED,
values,
null,
id,
version,
LockMode.NONE,
true,
subclassPersister,
false,
entry.areLazyPropertiesUnfetched()
);
subclassPersister.afterInitialize( result, entry.areLazyPropertiesUnfetched(), session );
persistenceContext.initializeNonLazyCollections();
// upgrade the lock if necessary:
//lock(result, lockMode);
//PostLoad is needed for EJB3
//TODO: reuse the PostLoadEvent...
PostLoadEvent postLoadEvent = new PostLoadEvent(session).setEntity(result)
.setId(id).setPersister(persister);
PostLoadEventListener[] listeners = session.getListeners().getPostLoadEventListeners();
for ( int i = 0; i < listeners.length; i++ ) {
listeners[i].onPostLoad(postLoadEvent);
}
return result;
}
}
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