Hibernate optimist locking code snippet #14

snippet.groovy

book = Book.get(id)
…
// make some changes to book
… 

// Now we are at a point when the session is flushing/committing…

// Obtain lock. If stale, re-load locked and
// merge our existing *dirty* properties according to
// merge policies:
// Changes we've made will overwrite anything new from the DB
book = book.lockAndMergeSessionIn()

// … or … 
// Changes to the DB will survive, anything we changed
// that did not change in the DB survives also
book = book.lockAndMergeDatabaseIn()

// … or … 
// Exactly the values we have for all properties will be used
// all values from the DB will be lost even if changed and 
// they weren't change in this session (coherent "squash" update)
book = book.lockAndOverwrite()

// … or … 
// Changes to the DB will survive, anything we also changed
// will be lost
book = book.lockAndResolve { conflicts, storedInstance ->
    for (conflict in conflicts) {
        switch (conflict) {
            case 'title':
                storedInstance.title = book.title
                break
            case 'author':
                storedInstance.author = book.author
                break;
            case 'genresList':
                storedInstance.genresList = book.genresList.clone()
                break;
            default:
                log.debug "Conflicting property value: ${conflict}"
                storedInstance[conflict.name] = storedInstance[name]
        }
    }
}

// … or when we need to know what we have is stale … 
boolean objectIsStale = book.lockOrFail()