IdGeneratorHolder.cs :  » Persistence-Frameworks » Persist.NET » Persist » IdGenerators » C# / CSharp Open Source

// Persist library : Persistence layer
// Copyright (C) 2003 Vincent Daron
// 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
// 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
// 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

using System;
using Persist.Config;
using System.Collections.Specialized;

namespace Persist.IdGenerators{
  /// <summary>
  /// This class manage an IdGenerator object
  /// </summary>
   class IdGeneratorHolder
   {
      private NameValueCollection theParameters = null;
      private Type theIdGeneratorType           = null;
      private IIdGenerator theInstance          = null;
      private bool IsSingleInstance             = false;
      private bool isInitialized                = false;
      private string theName;
      private string theTypeName;
      
      /// <summary>
      /// Constructor
      /// </summary>
      /// <param name="name">the IIdGenerator name</param>
      /// <param name="idGeneratorTypeName">the IIdGenerator Type name</param>
      /// <param name="parameters">the parameters used during the IIdGenerator Initialization</param>
      /// <param name="singleInstance">Specified if it must have only one instance of the IIdGenerator</param>
      public IdGeneratorHolder(string name,string idGeneratorTypeName, NameValueCollection parameters, bool singleInstance)
      {
         theName = name;
         theTypeName = idGeneratorTypeName;
         theParameters = parameters;
         IsSingleInstance = singleInstance;
      }

      /// <summary>
      /// the IIdGenerator name
      /// Throw an exception if the IdGeneratorHolder is already initialized
      /// </summary>
      public string Name
      {
         get{return theName;}
         set
         {
            if(isInitialized)throw new Exception("the Name of the IdGeneratorHodler cannot be changed once initialized");
            theName = value;
         }
      }

      /// <summary>
      /// the IIdGenerator Type name
      /// Throw an exception if the IdGeneratorHolder is already initialized
      /// </summary>
      public string TypeName
      {
         get{return theTypeName;}
         set
         {
            if(isInitialized)throw new Exception("the TypeName of the IdGeneratorHodler cannot be changed once initialized");
            theTypeName = value;
         }
      }

      /// <summary>
      /// Specified if it must have only one instance of the IIdGenerator
      /// Throw an exception if the IdGeneratorHolder is already initialized
      /// </summary>
      public bool SingleInstance
      {
         get{return IsSingleInstance;}
         set
         {
            if(isInitialized)throw new Exception("the SingleInstance flag of the IdGeneratorHodler cannot be changed once initialized");
            IsSingleInstance = value;
         }
      }
      /// <summary>
      /// The IdGenerator Parameters used during initialization
      /// Any changes after initialization will not be taken into account
      /// </summary>
      public NameValueCollection Parameters
      {
         get{return theParameters;}
      }

      /// <summary>
      /// Initialize IdGeneratorHolder
      /// Throw an exception if the TypeName is not found
      /// </summary>
      public void Init()
      {
         lock(this)
         {
            try
            {
               theIdGeneratorType = System.Type.GetType(theTypeName,true);
               isInitialized = true;
            }
            catch(Exception e)
            {
               throw new ConfigurationException("IIdGenerator class with name " + theTypeName + " not found",e);
            }
         }
      }

      /// <summary>
      /// Return the IIdGenerator Instance
      /// Throw a ConfigurationException id not Initialized
      /// </summary>
      public IIdGenerator Instance
      {
         get
         {
            IIdGenerator result = null;

            lock(typeof(IdGeneratorHolder))
            {
               if(!isInitialized)
               {
                  throw new Exception("IdGeneratorHolder not initialized");
               }

               if(!IsSingleInstance)
               {
                  result =  GetNewInstance();
               }
               else
               {
                  if(theInstance == null)
                  {
                     theInstance = GetNewInstance();
                  }

                  result = theInstance;
               }
            }
            return result;
         }
      }


      /// <summary>
      /// Create a new Instance of the IIdGenerator
      /// Throw an exception if an error occurs during creation
      /// </summary>
      /// <returns></returns>
      private IIdGenerator GetNewInstance()
      {
         IIdGenerator idGen = (IIdGenerator)Activator.CreateInstance(theIdGeneratorType);
         idGen.Init(theParameters);
         return idGen;
      }
   }
}