dataaccesscontext.cs

该文件是多层体系结构的数据访问层

#region Copyright & License
//
// $Copyright:$
//
#endregion
#region Document Information
// $Author: Bai.shijun $
// $Rev: 558 $ 
// $Date: 05-10-08 16:12 $
#endregion

using System;
using System.Collections.Generic;
using System.Text;
using System.EnterpriseServices;

using Eai.Data;
using Eai.Data.Transaction;

namespace Eai.Data
{
    public class DataAccessContext : IDisposable
    {
        internal const string DefaultCreatorName = "default";
        private static object syncObj = new Object();
        private IDictionary<string, IDataAccessorCreator> daCreators = new Dictionary<string, IDataAccessorCreator>();

        /// <summary>
        /// DataAccessorCreator list.
        /// </summary>
        private static IDictionary<string, IDataAccessorCreator> GlobalDataAccessorCreators = new Dictionary<string, IDataAccessorCreator>(10);

        static DataAccessContext()
        {
            foreach (IDataAccessorCreatorConfig creatorConfig in Setting.Current.DataAccessorCreators.Values)
            {
                string name = creatorConfig.Name;
                string typeName = creatorConfig.Type;
                Type type = Type.GetType(typeName);
                IDataAccessorCreator creator = (IDataAccessorCreator)Activator.CreateInstance(type);
                creator.Config = creatorConfig;

                GlobalDataAccessorCreators.Add(name, creator);
            }
        }

        private DataAccessContext()
        {
        }

        [ThreadStatic]
        private static DataAccessContext currentContext;
        public static DataAccessContext Current
        {
            get 
            {
                if (currentContext == null)
                {
                    lock (syncObj)
                    {
                        if (currentContext == null)
                        {
                            currentContext = new DataAccessContext();
                            IEnumerator<KeyValuePair<string, IDataAccessorCreator>> 
                                e = GlobalDataAccessorCreators.GetEnumerator();
                            for (; e.MoveNext(); )
                            {
                                string key = e.Current.Key;
                                IDataAccessorCreator creator = e.Current.Value;
                                currentContext.daCreators.Add(key, creator);
                            }
                        }
                    }
                }

                return currentContext;
            }
        }
        
        public void RenewDataAccessor()
        {
            dataAccessors.Clear();
        }

        private IDictionary<string, IDataAccessor> dataAccessors = new Dictionary<string, IDataAccessor>();
        public IDataAccessor GetDataAccessor()
        {
            return GetDataAccessor(DefaultCreatorName);
        }

        public IDataAccessor GetDataAccessor(string dataAccessorName)
        {
            IDataAccessor dataAccessor = null;

            TransactionManager transManager = TransactionManager.Instance;
            if (transManager.IsInTransaction)
            {
                dataAccessor = transManager.CurrentTransaction.GetDataAccessor(dataAccessorName);
                if (dataAccessor == null)
                {
                    dataAccessor = CreateDataAccessor(dataAccessorName);
                    transManager.CurrentTransaction.AttachDataAccessor(dataAccessorName, dataAccessor);
                }
            }
            else
            {
                if (dataAccessors.ContainsKey(dataAccessorName)) dataAccessor = dataAccessors[dataAccessorName];
                if (dataAccessor == null)
                {
                    dataAccessor = CreateDataAccessor(dataAccessorName);
                    dataAccessors.Add(dataAccessorName, dataAccessor);
                }
            }

            return dataAccessor;
        }

        private IDataAccessor CreateDataAccessor(string dataAccessorName)
        {
            if (!daCreators.ContainsKey(dataAccessorName))
            {
                throw new Exception("Not existed name '" + dataAccessorName + "' DataAccessorCreator.");
            }

            IDataAccessorCreator creator = daCreators[dataAccessorName];
            IDataAccessor dataAccessor = creator.Create();
            return dataAccessor;
        }

        #region IDisposable Members

        public void Dispose()
        {
            ;
        }

        #endregion

        #region only for test

#if DEBUG
        public IDictionary<string, IDataAccessorCreator> DataAccessorCreators
        {
            get { return daCreators; }
        }
#endif
        #endregion
    }
}