SessionFactory负责构建Session实例,就像在Configuration解析中,首先给出的那段代码:
private static SessionFactory sf = null;
static{
Configuration configuration = new Configuration();
configuration.configure("cn/huawei/config/hibernate.cfg.xml");
configuration.addClass(Customer.class);
sf = configuration.buildSessionFactory();
}
configuration.buildSessionFactory()方法来返回Session的实例。那么hibernate程序是如何构建Session的实例的呢?我们从代码中找找看,当然这还是离不开Configuration这个类,还是得从这个类开始,找到buildSessionFactory()这个方法。看下面的代码:
public SessionFactory buildSessionFactory() throws HibernateException {
log.debug( "Preparing to build session factory with filters : " + filterDefinitions );
secondPassCompile();
validate();
Environment.verifyProperties( properties );
Properties copy = new Properties();
copy.putAll( properties );
PropertiesHelper.resolvePlaceHolders( copy );
Settings settings = buildSettings( copy );
return new SessionFactoryImpl(
this,
mapping,
settings,
getInitializedEventListeners(),
sessionFactoryObserver
);
}
这个方法返回的是一个sessionFactory的实例。首先我们来分析一下这个方法,这个方法是先对property这个变量里的值进行了校验,至于怎么校验的,咱们一会儿再说,校验完了之后,程序直接返回了一个new SessionFactoryImpl(this,mapping,settings,getInitializedEventListeners(),sessionFactoryObserver);咱们看一下这个方法的原始模型:org.hibernate.impl.SessionFactoryImpl.SessionFactoryImpl(Configuration cfg, Mapping mapping, Settings settings, EventListeners listeners, SessionFactoryObserver observer) throws HibernateException
第一个参数是Configuration类的一个实例,第二个参数是mapping类的实例(里面是持久化类的一些属性),第三个参数是Settings类的实例,它通过buildSettings这个方法将配置文件中的值给解析出来方面以后使用;第四个参数是SessionFactoryObserver类型,主要的内容是观察SessionFactory打开还是关闭的。接下来我们就进入SessionFactoryImpl这个构造方法中去看看究竟:
public SessionFactoryImpl(
Configuration cfg,
Mapping mapping,
Settings settings,
EventListeners listeners,
SessionFactoryObserver observer) throws HibernateException {
log.info("building session factory");
Statistics concurrentStatistics = null;
try {
Class concurrentStatsClass = ReflectHelper.classForName("org.hibernate.stat.ConcurrentStatisticsImpl");
Constructor constructor = concurrentStatsClass.getConstructor(new Class[]{SessionFactoryImplementor.class});
concurrentStatistics = (Statistics) constructor.newInstance(new Object[]{this});
log.trace("JDK 1.5 concurrent classes present");
} catch ( NoClassDefFoundError noJava5 ) {
log.trace("JDK 1.5 concurrent classes missing");
} catch (Exception noJava5) {
log.trace("JDK 1.5 concurrent classes missing");
}
if (concurrentStatistics != null) {
this.statistics = concurrentStatistics;
} else {
this.statistics = new StatisticsImpl(this);
}
if ( log.isTraceEnabled() ) {
log.trace("Statistics initialized with " + statistics.getClass().getName());
}
this.properties = new Properties();
this.properties.putAll( cfg.getProperties() );
this.interceptor = cfg.getInterceptor();
this.settings = settings;
this.sqlFunctionRegistry = new SQLFunctionRegistry(settings.getDialect(), cfg.getSqlFunctions());
this.eventListeners = listeners;
this.observer = observer != null ? observer : new SessionFactoryObserver() {
public void sessionFactoryCreated(SessionFactory factory) {
}
public void sessionFactoryClosed(SessionFactory factory) {
}
};
this.filters = new HashMap();
this.filters.putAll( cfg.getFilterDefinitions() );
if ( log.isDebugEnabled() ) {
log.debug("Session factory constructed with filter configurations : " + filters);
}
if ( log.isDebugEnabled() ) {
log.debug(
"instantiating session factory with properties: " + properties
);
}
// Caches
settings.getRegionFactory().start( settings, properties );
//Generators:
identifierGenerators = new HashMap();
Iterator classes = cfg.getClassMappings();
while ( classes.hasNext() ) {
PersistentClass model = (PersistentClass) classes.next();
if ( !model.isInherited() ) {
IdentifierGenerator generator = model.getIdentifier().createIdentifierGenerator(
cfg.getIdentifierGeneratorFactory(),
settings.getDialect(),
settings.getDefaultCatalogName(),
settings.getDefaultSchemaName(),
(RootClass) model
);
identifierGenerators.put( model.getEntityName(), generator );
}
}
///////////////////////////////////////////////////////////////////////
// Prepare persisters and link them up with their cache
// region/access-strategy
final String cacheRegionPrefix = settings.getCacheRegionPrefix() == null ? "" : settings.getCacheRegionPrefix() + ".";
entityPersisters = new HashMap();
Map entityAccessStrategies = new HashMap();
Map classMeta = new HashMap();
classes = cfg.getClassMappings();
while ( classes.hasNext() ) {
final PersistentClass model = (PersistentClass) classes.next();
model.prepareTemporaryTables( mapping, settings.getDialect() );
final String cacheRegionName = cacheRegionPrefix + model.getRootClass().getCacheRegionName();
// cache region is defined by the root-class in the hierarchy...
EntityRegionAccessStrategy accessStrategy = ( EntityRegionAccessStrategy ) entityAccessStrategies.get( cacheRegionName );
if ( accessStrategy == null && settings.isSecondLevelCacheEnabled() ) {
final AccessType accessType = AccessType.parse( model.getCacheConcurrencyStrategy() );
if ( accessType != null ) {
log.trace( "Building cache for entity data [" + model.getEntityName() + "]" );
EntityRegion entityRegion = settings.getRegionFactory().buildEntityRegion( cacheRegionName, properties, CacheDataDescriptionImpl.decode( model ) );
accessStrategy = entityRegion.buildAccessStrategy( accessType );
entityAccessStrategies.put( cacheRegionName, accessStrategy );
allCacheRegions.put( cacheRegionName, entityRegion );
}
}
EntityPersister cp = PersisterFactory.createClassPersister( model, accessStrategy, this, mapping );
entityPersisters.put( model.getEntityName(), cp );
classMeta.put( model.getEntityName(), cp.getClassMetadata() );
}
classMetadata = Collections.unmodifiableMap(classMeta);
Map tmpEntityToCollectionRoleMap = new HashMap();
collectionPersisters = new HashMap();
Iterator collections = cfg.getCollectionMappings();
while ( collections.hasNext() ) {
Collection model = (Collection) collections.next();
final String cacheRegionName = cacheRegionPrefix + model.getCacheRegionName();
final AccessType accessType = AccessType.parse( model.getCacheConcurrencyStrategy() );
CollectionRegionAccessStrategy accessStrategy = null;
if ( accessType != null && settings.isSecondLevelCacheEnabled() ) {
log.trace( "Building cache for collection data [" + model.getRole() + "]" );
CollectionRegion collectionRegion = settings.getRegionFactory().buildCollectionRegion( cacheRegionName, properties, CacheDataDescriptionImpl.decode( model ) );
accessStrategy = collectionRegion.buildAccessStrategy( accessType );
entityAccessStrategies.put( cacheRegionName, accessStrategy );
allCacheRegions.put( cacheRegionName, collectionRegion );
}
CollectionPersister persister = PersisterFactory.createCollectionPersister( cfg, model, accessStrategy, this) ;
collectionPersisters.put( model.getRole(), persister.getCollectionMetadata() );
Type indexType = persister.getIndexType();
if ( indexType != null && indexType.isAssociationType() && !indexType.isAnyType() ) {
String entityName = ( ( AssociationType ) indexType ).getAssociatedEntityName( this );
Set roles = ( Set ) tmpEntityToCollectionRoleMap.get( entityName );
if ( roles == null ) {
roles = new HashSet();
tmpEntityToCollectionRoleMap.put( entityName, roles );
}
roles.add( persister.getRole() );
}
Type elementType = persister.getElementType();
if ( elementType.isAssociationType() && !elementType.isAnyType() ) {
String entityName = ( ( AssociationType ) elementType ).getAssociatedEntityName( this );
Set roles = ( Set ) tmpEntityToCollectionRoleMap.get( entityName );
if ( roles == null ) {
roles = new HashSet();
tmpEntityToCollectionRoleMap.put( entityName, roles );
}
roles.add( persister.getRole() );
}
}
collectionMetadata = Collections.unmodifiableMap(collectionPersisters);
Iterator itr = tmpEntityToCollectionRoleMap.entrySet().iterator();
while ( itr.hasNext() ) {
final Map.Entry entry = ( Map.Entry ) itr.next();
entry.setValue( Collections.unmodifiableSet( ( Set ) entry.getValue() ) );
}
collectionRolesByEntityParticipant = Collections.unmodifiableMap( tmpEntityToCollectionRoleMap );
//Named Queries:
namedQueries = new HashMap( cfg.getNamedQueries() );
namedSqlQueries = new HashMap( cfg.getNamedSQLQueries() );
sqlResultSetMappings = new HashMap( cfg.getSqlResultSetMappings() );
imports = new HashMap( cfg.getImports() );
// after *all* persisters and named queries are registered
Iterator iter = entityPersisters.values().iterator();
while ( iter.hasNext() ) {
final EntityPersister persister = ( ( EntityPersister ) iter.next() );
persister.postInstantiate();
registerEntityNameResolvers( persister );
}
iter = collectionPersisters.values().iterator();
while ( iter.hasNext() ) {
final CollectionPersister persister = ( ( CollectionPersister ) iter.next() );
persister.postInstantiate();
}
//JNDI + Serialization:
name = settings.getSessionFactoryName();
try {
uuid = (String) UUID_GENERATOR.generate(null, null);
}
catch (Exception e) {
throw new AssertionFailure("Could not generate UUID");
}
SessionFactoryObjectFactory.addInstance(uuid, name, this, properties);
log.debug("instantiated session factory");
if ( settings.isAutoCreateSchema() ) {
new SchemaExport( cfg, settings ).create( false, true );
}
if ( settings.isAutoUpdateSchema() ) {
new SchemaUpdate( cfg, settings ).execute( false, true );
}
if ( settings.isAutoValidateSchema() ) {
new SchemaValidator( cfg, settings ).validate();
}
if ( settings.isAutoDropSchema() ) {
schemaExport = new SchemaExport( cfg, settings );
}
if ( settings.getTransactionManagerLookup()!=null ) {
log.debug("obtaining JTA TransactionManager");
transactionManager = settings.getTransactionManagerLookup().getTransactionManager(properties);
}
else {
if ( settings.getTransactionFactory().isTransactionManagerRequired() ) {
throw new HibernateException("The chosen transaction strategy requires access to the JTA TransactionManager");
}
transactionManager = null;
}
currentSessionContext = buildCurrentSessionContext();
if ( settings.isQueryCacheEnabled() ) {
updateTimestampsCache = new UpdateTimestampsCache(settings, properties);
queryCache = settings.getQueryCacheFactory()
.getQueryCache(null, updateTimestampsCache, settings, properties);
queryCaches = new HashMap();
allCacheRegions.put( updateTimestampsCache.getRegion().getName(), updateTimestampsCache.getRegion() );
allCacheRegions.put( queryCache.getRegion().getName(), queryCache.getRegion() );
}
else {
updateTimestampsCache = null;
queryCache = null;
queryCaches = null;
}
//checking for named queries
if ( settings.isNamedQueryStartupCheckingEnabled() ) {
Map errors = checkNamedQueries();
if ( !errors.isEmpty() ) {
Set keys = errors.keySet();
StringBuffer failingQueries = new StringBuffer( "Errors in named queries: " );
for ( Iterator iterator = keys.iterator() ; iterator.hasNext() ; ) {
String queryName = ( String ) iterator.next();
HibernateException e = ( HibernateException ) errors.get( queryName );
failingQueries.append( queryName );
if ( iterator.hasNext() ) {
failingQueries.append( ", " );
}
log.error( "Error in named query: " + queryName, e );
}
throw new HibernateException( failingQueries.toString() );
}
}
//stats
getStatistics().setStatisticsEnabled( settings.isStatisticsEnabled() );
// EntityNotFoundDelegate
EntityNotFoundDelegate entityNotFoundDelegate = cfg.getEntityNotFoundDelegate();
if ( entityNotFoundDelegate == null ) {
entityNotFoundDelegate = new EntityNotFoundDelegate() {
public void handleEntityNotFound(String entityName, Serializable id) {
throw new ObjectNotFoundException( id, entityName );
}
public boolean isEntityNotFoundException(RuntimeException exception) {
return ObjectNotFoundException.class.isInstance( exception );
}
};
}
this.entityNotFoundDelegate = entityNotFoundDelegate;
// this needs to happen after persisters are all ready to go...
this.fetchProfiles = new HashMap();
itr = cfg.iterateFetchProfiles();
while ( itr.hasNext() ) {
final org.hibernate.mapping.FetchProfile mappingProfile =
( org.hibernate.mapping.FetchProfile ) itr.next();
final FetchProfile fetchProfile = new FetchProfile( mappingProfile.getName() );
Iterator fetches = mappingProfile.getFetches().iterator();
while ( fetches.hasNext() ) {
final org.hibernate.mapping.FetchProfile.Fetch mappingFetch =
( org.hibernate.mapping.FetchProfile.Fetch ) fetches.next();
// resolve the persister owning the fetch
final String entityName = getImportedClassName( mappingFetch.getEntity() );
final EntityPersister owner = ( EntityPersister ) ( entityName == null ? null : entityPersisters.get( entityName ) );
if ( owner == null ) {
throw new HibernateException(
"Unable to resolve entity reference [" + mappingFetch.getEntity()
+ "] in fetch profile [" + fetchProfile.getName() + "]"
);
}
// validate the specified association fetch
Type associationType = owner.getPropertyType( mappingFetch.getAssociation() );
if ( associationType == null || !associationType.isAssociationType() ) {
throw new HibernateException( "Fetch profile [" + fetchProfile.getName() + "] specified an invalid association" );
}
// resolve the style
final Fetch.Style fetchStyle = Fetch.Style.parse( mappingFetch.getStyle() );
// then construct the fetch instance...
fetchProfile.addFetch( new Association( owner, mappingFetch.getAssociation() ), fetchStyle );
( ( Loadable ) owner ).registerAffectingFetchProfile( fetchProfile.getName() );
}
fetchProfiles.put( fetchProfile.getName(), fetchProfile );
}
this.observer.sessionFactoryCreated( this );
}
看这段代码的最后一行this.observer.sessionFactoryCreated( this );通过这个SessionFactoryObserver将SessionFactory创建出来。