使用NHibernate中的拦截器（续）

我的前一篇随笔《使用NHibernate中的拦截器》中简单讲述了如何使用接口IInterceptor拦截CRUD操作。但没有区分开新增和修改操作。
对于public bool OnSave(object entity, object id, object[] state, string[] propertyNames, NHibernate.Type.IType[] types)会在Insert new object之前触发，而public void PreFlush(System.Collections.ICollection entities)则是Update old Object之前和Insert New Object之后都会触发的。为了记录下来明确的实体的insert和update操作，需要将其区分开。所以我查看了NHIbernate的源码，发现Insert  new object到了调用PreFlush后，其ID字段（属性）就有值了，而在OnSave时是为0或者null或者其它配置文件中定义的unsaved-value。通常为了简单，都是使用子动增长的字段作为ID的。所以我写了下面的代码来分别记录“新增”和“修改”的操作：

    /**//// <summary>
    /// CRUD日志记录类
    /// </summary>
    public class LogInterceptor : IInterceptor
    {
                
        private Hashtable _entity = null;
        private Type _entityType = null;
        private IEntityManager manager = null;
        public LogInterceptor()
        {
            manager = EntityManager.CreateEntityManager();
        }
        IInterceptor 成员#region IInterceptor 成员

                  //省略其他必须实现的方法
        public bool OnSave(object entity, object id, object[] state, string[] propertyNames, NHibernate.Type.IType[] types)
        {
            // Insert New Object之前会触发
            if ( manager.Factory != null )
            {
                this._entityType = entity.GetType();
                this._entity = Copy(state,propertyNames);
            }
            else
            {
                this._entity = null;
                this._entityType = null;
            }
            this.AddLog(entity,id,state,propertyNames,"新增"); 
            return false;
        }

        public void OnDelete(object entity, object id, object[] state, string[] propertyNames, NHibernate.Type.IType[] types)
        {
            this.AddLog(entity,id,state,propertyNames,"删除");
        }

        public void PreFlush(System.Collections.ICollection entities)
        {
            // Update old Object之前会触发
            // Insert New Object之后会触发
            if ( entities.Count >0 )
            {    
                //过滤掉Insert New Object
                AddLog(entities,"修改");
            }
        }
        #endregion

        private Hashtable Copy(object[] state, string[] propertyNames)
        {
            _entity = new Hashtable();
            for ( int i=0;i<state.Length;i++)
            {
                _entity.Add(propertyNames[i],state[i]);
            }
            return _entity;
        }
        private void AddLog(object entity,object entityID,object[] state,string[] propertyNames,string operType)
        {
            try
            {
                                //如果是日志类自己的话，就不再记录了
                if ( entity.GetType() == typeof(DAL.SMS.SM_Log))
                    return;
                Log log = Log.CreateLog();
                StringBuilder states = new StringBuilder();
                for ( int i=0;i<state.Length;i++)
                {
                    if ( state[i] == null )
                        continue;
                    string pName = propertyNames[i];
                    if ( log.dsEntity != null )
                    {
                        DataRow[] rows = log.dsEntity.Tables[0].Select("Entity='"+entity.ToString()+"' and Property='"+pName+"'");
                        if ( rows != null && rows.Length>0 )
                        {
                            pName = rows[0]["PropertyName"].ToString();
                        }
                    }
                    states.Append("|| "+pName+"--"+state[i].ToString()+" ||\t\r");
                }
                log.Add(entity.ToString(),entityID.ToString(),states.ToString(),operType);
            }
            catch
            {}
        }

        private void AddLog(ICollection entities,string operType)
        {
            try
            {
                IEnumerator e = entities.GetEnumerator();
                while (e.MoveNext())
                {
                    Type type = e.Current.GetType();
                    if ( type == typeof(DAL.SMS.SM_Log))
                        continue;
                    PropertyInfo[] pi = type.GetProperties(BindingFlags.Public | BindingFlags.Instance);
                    string[] propertyNames = new string[pi.Length];
                    object[] state = new object[pi.Length];
                    object id = e.Current;
                    string idName = manager.Factory.GetPersister(type).IdentifierPropertyName;
                    if (this._entityType != null && type == _entityType)
                    {
                        bool isNewObject = true;
                        for (int i=0;i<pi.Length;i++)
                        {
                            if ( pi[i].Name != idName)
                            {
                                object v = pi[i].GetValue(e.Current,null);
                                isNewObject &= (_entity[pi[i].Name].ToString() == v.ToString());
                            }
                        }
                        if ( isNewObject )
                        {
                            continue;
                        }
                    }
                    for(int i=0;i<pi.Length;i++)
                    {
                        propertyNames[i]= pi[i].Name;
                        state[i]= pi[i].GetValue(e.Current,null);
                        if ( pi[i].Name == idName )
                        {
                            id = state[i];
                        }
                    }
                    this.AddLog(e.Current,id,state,propertyNames,operType);
                    this._entity = null;
                    this._entityType = null;
                }
            }
            catch
            {}
        }
    }

上面代码中的private IEntityManager manager = null;是一个用来管理session的管理器，提供了一个属性public ISessionFactoryImplementor Factory，通过该属性才能方面地得知实体类的ID属性的名字：

public sealed class EntityManager : IEntityManager
{
   private static ISessionFactory nSessionFactory = null;
   //
   public ISessionFactoryImplementor Factory
   {
    get {return nSessionFactory as ISessionFactoryImplementor;}
    }
}

获得ID属性的名字：

string idName = manager.Factory.GetPersister(type).IdentifierPropertyName;

于是现在可以比较粗略地记录下CRUD操作了……