selectManyCheckbox LazyInitializationException on process validation

Question

It appears that if you use a selectManyCheckbox backed by a set that is proxied by hibernate you will run into problems with the dreaded LazyInitializationException. This has no

Answer 1

Thanks for the hint to use the collectionType attribute for h:selectMany tags to prevent the LazyInitializationException.

However, instead of flaming about it in an inappropriate forum, how about learning what's new in JSF 2.0, and posting a full example of this problem and how to fix it?

Groundwork:

• Mojarra 2.1 is the JSF 2 Reference Implementation (see What is Mojarra)
• h:selectManyCheckbox VLD documentation describes how to use the collectionType attribute (new in JSF 2.0)
• this problem affects validation of h:selectManyCheckbox, h:selectManyListBox, and h:selectManyMenu tags

Stack Trace of this error:

Feb 04, 2013 1:20:50 PM com.sun.faces.lifecycle.ProcessValidationsPhase execute WARNING: failed to lazily initialize a collection, no session or session was closed org.hibernate.LazyInitializationException: failed to lazily initialize a collection, no session or session was closed at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationException(AbstractPersistentCollection.java:383) at org.hibernate.collection.AbstractPersistentCollection.throwLazyInitializationExceptionIfNotConnected(AbstractPersistentCollection.java:375) at org.hibernate.collection.AbstractPersistentCollection.readSize(AbstractPersistentCollection.java:122) at org.hibernate.collection.PersistentBag.isEmpty(PersistentBag.java:255) at javax.faces.component.UIInput.isEmpty(UIInput.java:1257) at javax.faces.component.UIInput.validateValue(UIInput.java:1144) at javax.faces.component.UISelectMany.validateValue(UISelectMany.java:579)

Example adding collectionType to fix this error (I am using a custom validator):