org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: *class name here*, no session or session was closed

Use attach() to attach the fetched object to the current session.

def children = ne.children
children.eachWithIndex { ne, index -> log.info ne.name }

ne.attach()
def children = ne.children
children.eachWithIndex { ne, index -> log.info ne.name }

org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [*domainName*#*domain ID*]

org.springframework.orm.hibernate3.HibernateOptimisticLockingFailureException: Object of class [com.errigal.ticketer.Ticket] with identifier [510111]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [com.errigal.ticketer.Ticket#510111]

org.springframework.dao.DuplicateKeyException: a different object with the same identifier value was already associated with the session: [com.errigal.ticketer.TicketStatus#591611]; nested exception is org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [com.errigal.ticketer.TicketStatus#591611]

Use attach() to attach the fetched object to the current session.

Use merge() to attach the changes made to the object by different session/transaction to the current session object.

Fetch the required object ID before starting a new session and then create an new object inside the newly started session using its id, update the required values, and then save.

arg , defaultArg , ticket ->

Long ticketId = ticket.id
com.errigal.ticketer.Ticket.withNewSession { sess ->
    def newTicket = com.errigal.ticketer.Ticket.get(ticketId)
    newTicket.dueDate = new Date()
    newTicket.priority = 1 as Integer
    newTicket.save()
    log.info "Set Due Date of Ticket ${newTicket.id} to be ${newTicket.dueDate} and Priority to ${newTicket.priority}."
    sess.flush()
}

log.info "Check: Ticket ${ticket.id} Due Date ${ticket.dueDate} and Priority ${ticket.priority}."