The variable sn is null, there is no snapshot of the set. sn.size() causes the NPE

Hibernate version:

2.1

Mapping documents:

<set name="logs" lazy="true" inverse="false" cascade="none" sort="natural">
<key column="subject"/>
<composite-element class="org.concern.controller.Log">
<property name="activity"
type="java.lang.String"
update="true"
insert="true"
column="activity"
length="64"/>

<property name="success"
type="boolean"
update="true"
insert="true"
column="success"/>

<property name="message"
type="java.lang.String"
update="true"
insert="true"
column="message"
length="512"/>

<property name="details"
type="java.lang.String"
update="true"
insert="true"
column="details"
length="512"/>

<property name="timestamp"
type="java.sql.Timestamp"
update="true"
insert="true"
column="timestamp"/>
</composite-element>
</set>

Code between sessionFactory.openSession() and session.close():

sessions.getSession().lock(subject, LockMode.UPGRADE);
subject.setDestroyed(true);
Log log = new Log("", "DESTROYED");
log.setSuccess(true);
if (subject.getLogs() == null)
subject.setLogs(new TreeSet());
subject.getLogs().add(log);

Full stack trace of any exception that occurs:

java.lang.NullPointerException
at net.sf.hibernate.collection.Set.equalsSnapshot(Set.java:54)
at net.sf.hibernate.impl.SessionImpl$CollectionEntry.isDirty(SessionImpl.java:328)
at net.sf.hibernate.impl.SessionImpl$CollectionEntry.preFlush(SessionImpl.java:336)
at net.sf.hibernate.impl.SessionImpl.preFlushCollections(SessionImpl.java:2738)
at net.sf.hibernate.impl.SessionImpl.flushEverything(SessionImpl.java:2201)
at net.sf.hibernate.impl.SessionImpl.flush(SessionImpl.java:2186)
at net.sf.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:61)
[...]

Debug level Hibernate log excerpt:

Hibernate: select subject0_.id as x0_0_ from Subject subject0_ where (subject0_.userValue=? )
Hibernate: select subject0_.id as id0_, subject0_.userValue as userValue0_, subject0_.locked as locked0_, subject0_.destroyed as destroyed0_ from Subject subject0_ where subject0_.id=?
Hibernate: select id from Subject where id =? for update
Hibernate: select timers0_.timeout as timeout__, timers0_.subject as subject__ from timers timers0_ where timers0_.subject=?
Hibernate: select logs0_.activity as activity__, logs0_.success as success__, logs0_.message as message__, logs0_.details as details__, logs0_.timestamp as timestamp__, logs0_.subject as subject__ from logs logs0_ where logs0_.subject=?

I guess you have changed the object since you detached it, and changed the collection reference. This is not allowed if you are going to use lock().

I will try and track down the cause and make Hibernate throw a more helpful exception. NPEs are always bad.

It would help me a lot if you could submit a very simple test case to JIRA. Thanks.

No. I was even more stupid:

The Log class had bad equals and hashCode methods, that presumably threw NPEs. I changed them and now it's working. Probably those NPEs in equals or hashCode prevented hibernate from making the snapshot.

It would have helped a lot, if hibernate wouldn't swalllow those exceptions.



Do you still need a test case?

Thanks a lot,

Holger

Hibernate doesn't swallow any exceptions, so its kinda confusing...