abstractlockupgradeeventlistener.cs

NHibernate NET开发者所需的

using System;
using log4net;
using NHibernate.Cache;
using NHibernate.Engine;
using NHibernate.Impl;
using NHibernate.Persister.Entity;
using Status=NHibernate.Engine.Status;

namespace NHibernate.Event.Default
{
	/// <summary> 
	/// A convenience base class for listeners that respond to requests to perform a
	/// pessimistic lock upgrade on an entity. 
	/// </summary>
	[Serializable]
	public class AbstractLockUpgradeEventListener : AbstractReassociateEventListener
	{
		private static readonly ILog log = LogManager.GetLogger(typeof(AbstractLockUpgradeEventListener));

		/// <summary> 
		/// Performs a pessimistic lock upgrade on a given entity, if needed. 
		/// </summary>
		/// <param name="entity">The entity for which to upgrade the lock.</param>
		/// <param name="entry">The entity's EntityEntry instance.</param>
		/// <param name="requestedLockMode">The lock mode being requested for locking. </param>
		/// <param name="source">The session which is the source of the event being processed.</param>
		protected virtual void UpgradeLock(object entity, EntityEntry entry, LockMode requestedLockMode, ISessionImplementor source)
		{
			if (requestedLockMode.GreaterThan(entry.LockMode))
			{
				// The user requested a "greater" (i.e. more restrictive) form of
				// pessimistic lock
				if (entry.Status != Status.Loaded)
				{
					throw new ObjectDeletedException("attempted to lock a deleted instance", entry.Id, entry.EntityName);
				}

				IEntityPersister persister = entry.Persister;

				if (log.IsDebugEnabled)
				{
					log.Debug(string.Format("locking {0} in mode: {1}", MessageHelper.InfoString(persister, entry.Id, source.Factory), requestedLockMode));
				}

				ISoftLock slock;
				CacheKey ck;
				if (persister.HasCache)
				{
					ck = new CacheKey(entry.Id, persister.IdentifierType, persister.RootEntityName, source.EntityMode, source.Factory);
					slock = persister.Cache.Lock(ck, entry.Version);
				}
				else
				{
					ck = null;
					slock = null;
				}

				try
				{
					if (persister.IsVersioned && requestedLockMode == LockMode.Force)
					{
						// todo : should we check the current isolation mode explicitly?
						object nextVersion = persister.ForceVersionIncrement(entry.Id, entry.Version, source);
						entry.ForceLocked(entity, nextVersion);
					}
					else
					{
						persister.Lock(entry.Id, entry.Version, entity, requestedLockMode, source);
					}
					entry.LockMode = requestedLockMode;
				}
				finally
				{
					// the database now holds a lock + the object is flushed from the cache,
					// so release the soft lock
					if (persister.HasCache)
					{
						persister.Cache.Release(ck, slock);
					}
				}
			}
		}
	}
}