Hello,

I wrote a UserType to serialize a Map variable to a varchar column. I included the code for this below. It works fine for inserting. But when I attempt to retrieve (after restarting JBoss) the parent business object, TaskVO, I get a LazyInitializationException.

Any ideas on the cause? FYI I'm retrieving a collection of TaskVOs via a stateless Session Bean, so EJBs are involved. One other note - our serializer uses an XML Serializer we wrote because Sun's XmlEncoder is so poor compared to C# XmlSerializer.

Here is the descriptor for TaskVO business object:



Here is the stack trace:

[code]
11:23:41,533 ERROR [LazyInitializationException] Failed to lazily initialize a c
ollection - no Session
net.sf.hibernate.LazyInitializationException: Failed to lazily initialize a coll
ection - no Session
at net.sf.hibernate.collection.PersistentCollection.initialize(Persisten
tCollection.java:167)
at net.sf.hibernate.collection.PersistentCollection.read(PersistentColle
ction.java:64)
at net.sf.hibernate.collection.Set.equals(Set.java:384)
at java.util.ArrayList.indexOf(ArrayList.java:216)
at java.util.ArrayList.contains(ArrayList.java:197)
at com.teradata.tap.system.xml.Decoder.startNode(Decoder.java:187)
at com.teradata.tap.system.xml.Handler.startElement(Handler.java:45)
at org.apache.xerces.parsers.AbstractSAXParser.startElement(AbstractSAXP
arser.java:452)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanStartElemen
t(XMLDocumentFragmentScannerImpl.java:821)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl$FragmentContent
Dispatcher.dispatch(XMLDocumentFragmentScannerImpl.java:1541)
at org.apache.xerces.impl.XMLDocumentFragmentScannerImpl.scanDocument(XM
LDocumentFragmentScannerImpl.java:346)
at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.jav
a:529)
at org.apache.xerces.parsers.DTDConfiguration.parse(DTDConfiguration.jav
a:585)
at org.apache.xerces.parsers.XMLParser.parse(XMLParser.java:152)
at org.apache.xerces.parsers.AbstractSAXParser.parse(AbstractSAXParser.j
ava:1142)
at javax.xml.parsers.SAXParser.parse(SAXParser.java:345)
at com.teradata.tap.system.xml.Decoder.<init>(Decoder.java:64)
at net.sf.hibernate.tap.MapUserType.nullSafeGet(MapUserType.java:112)
at net.sf.hibernate.type.CustomType.nullSafeGet(CustomType.java:97)
at net.sf.hibernate.type.AbstractType.hydrate(AbstractType.java:66)
at net.sf.hibernate.loader.Loader.hydrate(Loader.java:419)
at net.sf.hibernate.loader.Loader.loadFromResultSet(Loader.java:373)
at net.sf.hibernate.loader.Loader.instanceNotYetLoaded(Loader.java:342)
at net.sf.hibernate.loader.Loader.getRow(Loader.java:281)
at net.sf.hibernate.loader.Loader.doFind(Loader.java:159)
at net.sf.hibernate.loader.Loader.loadCollection(Loader.java:602)
at net.sf.hibernate.loader.OneToManyLoader.initialize(OneToManyLoader.ja
va:102)
at net.sf.hibernate.impl.SessionImpl.initialize(SessionImpl.java:2897)
at net.sf.hibernate.collection.PersistentCollection.getInitialValue(Pers
istentCollection.java:128)
at net.sf.hibernate.type.PersistentCollectionType.getCollection(Persiste
ntCollectionType.java:74)
at net.sf.hibernate.type.PersistentCollectionType.resolveIdentifier(Pers
istentCollectionType.java:177)
at net.sf.hibernate.impl.SessionImpl.initializeEntity(SessionImpl.java:1
959)
at net.sf.hibernate.loader.Loader.doFind(Loader.java:196)
at net.sf.hibernate.loader.Loader.find(Loader.java:620)
at net.sf.hibernate.loader.CriteriaLoader.list(CriteriaLoader.java:81)
at net.sf.hibernate.impl.SessionImpl.find(SessionImpl.java:3157)
at net.sf.hibernate.impl.CriteriaImpl.list(CriteriaImpl.java:65)
at com.teradata.tap.system.persistence.ejb.PersistenceManagerBean.getVec
tor(PersistenceManagerBean.java:1334)


And here is my MapUserType, nullSafeGet function:

[code]

public Object nullSafeGet(ResultSet rs, String[] names, Object owner) throws HibernateException, SQLException {

// Only 1 column
Object obj = rs.getObject(names[0]);
if (obj != null && obj.toString().length() > 0) {

Map map = null;
String input = obj.toString();

try{
Decoder decoder = new Decoder((String)input);
map = (Map) decoder.getObject();
}
catch(Exception e){
e.printStackTrace();
}

return map;
}

return null;
}
[/code]

Your Decoder is calling contains on a mapped collection at com.teradata.tap.system.xml.Decoder.startNode, and I strongly suspect you can't do that while the object is still constructed by Hibernate.

Well we are trying to understand exactly how Hibernate's Set constructor works. When we execute the following code, we get the same LazyInitializationException thrown. In our code, the Hibernate exception is always thrown on the call to .equals.

Why?

An Hibernate collection must be binded to a session. If not or if the session is closed, accessing the collection (if not previously initialized) will raise a LazyInitializationException.
equals() have to load the collection before comparing it (and it drives Gavin to despair ;-) )

Fyi, I ended up changing the client code so that it didn't attempt to serialize a Set using our UserType. But long term would be nice to find a away to accomplish this.