Question

我有一个事件监听器（用于审核日志），需要将审核日志条目附加到对象的关联中：

public Company : IAuditable {
    // Other stuff removed for bravety
    IAuditLog IAuditable.CreateEntry() {
        var entry = new CompanyAudit();
        this.auditLogs.Add(entry);
        return entry;
    }
    public virtual IEnumerable<CompanyAudit> AuditLogs {
        get { return this.auditLogs }
    }
}

AuditLogs集合使用级联：

进行映射

public class CompanyMap : ClassMap<Company> {
    public CompanyMap() {
        // Id and others removed fro bravety
        HasMany(x => x.AuditLogs).AsSet()
            .LazyLoad()
            .Access.ReadOnlyPropertyThroughCamelCaseField()
            .Cascade.All();
    }
}

监听器只是要求可审计对象创建日志条目，以便更新它们：

internal class AuditEventListener : IPreInsertEventListener, IPreUpdateEventListener {
    public bool OnPreUpdate(PreUpdateEvent ev) {
        var audit = ev.Entity as IAuditable;
        if (audit == null)
            return false;
        Log(audit);
        return false;
    }


    public bool OnPreInsert(PreInsertEvent ev) {
        var audit = ev.Entity as IAuditable;
        if (audit == null)
            return false;

        Log(audit);
        return false;
    }
    private static void Log(IAuditable auditable) {
        var entry = auditable.CreateAuditEntry();  // Doing this for every auditable property
        entry.CreatedAt = DateTime.Now;
        entry.Who = GetCurrentUser(); // Might potentially execute a query as it links current user with log entry
        // Also other information is set for entry here
    }
}

它的问题在于它在提交事务时抛出TransientObjectException：

NHibernate.TransientObjectException : object references an unsaved transient instance - save the transient instance before flushing. Type: CompanyAudit, Entity: CompanyAudit
    at NHibernate.Engine.ForeignKeys.GetEntityIdentifierIfNotUnsaved(String entityName, Object entity, ISessionImplementor session)
    at NHibernate.Type.EntityType.GetIdentifier(Object value, ISessionImplementor session)
    at NHibernate.Type.ManyToOneType.NullSafeSet(IDbCommand st, Object value, Int32 index, Boolean[] settable, ISessionImplementor session)
    at NHibernate.Persister.Collection.AbstractCollectionPersister.WriteElement(IDbCommand st, Object elt, Int32 i, ISessionImplementor session)
    at NHibernate.Persister.Collection.AbstractCollectionPersister.PerformInsert(Object ownerId, IPersistentCollection collection, IExpectation expectation, Object entry, Int32 index, Boolean useBatch, Boolean callable, ISessionImplementor session)
    at NHibernate.Persister.Collection.AbstractCollectionPersister.Recreate(IPersistentCollection collection, Object id, ISessionImplementor session)
    at NHibernate.Action.CollectionRecreateAction.Execute()
    at NHibernate.Engine.ActionQueue.Execute(IExecutable executable)
    at NHibernate.Engine.ActionQueue.ExecuteActions(IList list)
    at NHibernate.Engine.ActionQueue.ExecuteActions()
    at NHibernate.Event.Default.AbstractFlushingEventListener.PerformExecutions(IEventSource session)
    at NHibernate.Event.Default.DefaultFlushEventListener.OnFlush(FlushEvent event)
    at NHibernate.Impl.SessionImpl.Flush()
    at NHibernate.Transaction.AdoTransaction.Commit()

当级联设置为全部时，我希望NH能够处理这个问题。我还尝试使用state修改集合，但几乎同样如此。

所以问题是在保存之前修改对象关联的最后机会是什么？

谢谢，
德米特里。

Answer 1

http://ayende.com/Blog/archive/2009/04/29/nhibernate-ipreupdateeventlistener-amp-ipreinserteventlistener.aspx

缺点似乎是通过触发OnPreInsert，NHibernate已经确定了需要更新的内容。如果之后某些东西变脏了，你必须进一步更新“实体状态”，即“脏”对象列表中对象的条目。

您在公司上实施IAuditable会对该对象进行更改;即，将新对象添加到集合中。在创建全新对象的情况下，最佳实践（如Revin Hart在博客文章的评论中所提到的）似乎是创建子Session并将新对象保存在那里。这听起来比使用Set（）调用将所有必要条目添加到实体状态容易得多。尝试从IAuditable.CreateEntry（）调用中获取IAuditLog，并使用类似于以下内容的代码保存它：

public bool OnPreInsert(PreInsertEvent ev) {
    var audit = ev.Entity as IAuditable;
    if (audit == null)
        return false;

    var log = Log(audit);

    ISession newSession = ev.Source.PersistenceContext.Session.GetSession();
    newSession.Save(log);
    return false;
}


private static IAuditLog Log(IAuditable auditable) {
    var entry = auditable.CreateAuditEntry();  // Doing this for every auditable property
    entry.CreatedAt = DateTime.Now;
    entry.Who = GetCurrentUser(); // Might potentially execute a query as it links current user with log entry

    return entry;
}

Answer 2

我努力使用不同问题的NH的事件听众所以我只是决定使用Interceptor（基于EmptyInterceptor）。

我只需要覆盖SetSession，OnFlushDirty，OnSave方法并加入其中。

他们确实允许创建适当的对象并持久化它们。

到目前为止，这是最可行的解决方案。

在OnPreInsert，OnPreUpdate中将对象添加到关联

2 个答案: