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Introduction to Model Driven Development with Sculpture – Part 1

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3 Sep 2008CPOL15 min read 113.8K   759   124  
This article introduces how to create and manage .NET enterprise applications using your favorite technology (Data Access Application Block, LINQ, NHibernate, ASMX, and WCF) with the Model Driven Development approach by Sculpture.
//------------------------------------------------------------------------------
// <auto-generated>
//     This code was generated by Sculpture Code Generation Engine.
//     Changes to this file may cause incorrect behavior and will be lost if
//     the code is regenerated.
//     Generated On : 28/08/2008 06:20:10 م
// </auto-generated>
//------------------------------------------------------------------------------

using System.Runtime.Remoting.Messaging;
using System.Web;
using NHibernate;
using NHibernate.Cache;
using NHibernate.Cfg;

namespace DataAccess
{
    /// <summary>
    /// Handles creation and management of sessions and transactions.  It is a singleton because 
    /// building the initial session factory is very expensive. Inspiration for this class came 
    /// from Chapter 8 of Hibernate in Action by Bauer and King.  Although it is a sealed singleton
    /// you can use TypeMock (http://www.typemock.com) for more flexible testing.
    /// </summary>
    public sealed class NHibernateSessionManager
    {
        #region Thread-safe, lazy Singleton

        /// <summary>
        /// This is a thread-safe, lazy singleton.  See http://www.yoda.arachsys.com/csharp/singleton.html
        /// for more details about its implementation.
        /// </summary>
        public static NHibernateSessionManager Instance {
            get {
                return Nested.NHibernateSessionManager;
            }
        }

        /// <summary>
        /// Initializes the NHibernate session factory upon instantiation.
        /// </summary>
        private NHibernateSessionManager() {
            InitSessionFactory();
        }

        /// <summary>
        /// Assists with ensuring thread-safe, lazy singleton
        /// </summary>
        private class Nested
        {
            static Nested() { }
            internal static readonly NHibernateSessionManager NHibernateSessionManager = 
                new NHibernateSessionManager();
        }

        #endregion

        private void InitSessionFactory()
        {
            Configuration cfg = new Configuration();
            cfg.AddAssembly("Entities");
            sessionFactory = cfg.BuildSessionFactory();
        }

        /// <summary>
        /// Allows you to register an interceptor on a new session.  This may not be called if there is already
        /// an open session attached to the HttpContext.  If you have an interceptor to be used, modify
        /// the HttpModule to call this before calling BeginTransaction().
        /// </summary>
        public void RegisterInterceptor(IInterceptor interceptor) {
            ISession session = ContextSession;

            if (session != null && session.IsOpen) {
                throw new CacheException("You cannot register an interceptor once a session has already been opened");
            }

            GetSession(interceptor);
        }

        public ISession GetSession() {
            return GetSession(null);
        }

        /// <summary>
        /// Gets a session with or without an interceptor.  This method is not called directly; instead,
        /// it gets invoked from other public methods.
        /// </summary>
        private ISession GetSession(IInterceptor interceptor) {
            ISession session = ContextSession;

            if (session == null) {
                if (interceptor != null) {
                    session = sessionFactory.OpenSession(interceptor);
                }
                else {
                    session = sessionFactory.OpenSession();
                }

                ContextSession = session;
            }

            return session;
        }

        /// <summary>
        /// Flushes anything left in the session and closes the connection.
        /// </summary>
        public void CloseSession() {
            ISession session = ContextSession;

            if (session != null && session.IsOpen) {
                session.Flush();
                session.Close();
            }

            ContextSession = null;
        }

        public void BeginTransaction() {
            ITransaction transaction = ContextTransaction;

            if (transaction == null) {
                transaction = GetSession().BeginTransaction();
                ContextTransaction = transaction;
            }
        }

        public void CommitTransaction() {
            ITransaction transaction = ContextTransaction;

            try {
                if (HasOpenTransaction()) {
                    transaction.Commit();
                    ContextTransaction = null;
                }
            }
            catch (HibernateException) {
                RollbackTransaction();
                throw;
            }
        }

        public bool HasOpenTransaction() {
            ITransaction transaction = ContextTransaction;

            return transaction != null && !transaction.WasCommitted && !transaction.WasRolledBack;
        }

        public void RollbackTransaction() {
            ITransaction transaction = ContextTransaction;

            try {
                if (HasOpenTransaction()) {
                    transaction.Rollback();
                }

                ContextTransaction = null;
            }
            finally {
                CloseSession();
            }
        }

        /// <summary>
        /// If within a web context, this uses <see cref="HttpContext" /> instead of the WinForms 
        /// specific <see cref="CallContext" />.  Discussion concerning this found at 
        /// http://forum.springframework.net/showthread.php?t=572.
        /// </summary>
        private ITransaction ContextTransaction {
            get {
                if (IsInWebContext()) {
                    return (ITransaction)HttpContext.Current.Items[TRANSACTION_KEY];
                }
                else {
                    return (ITransaction)CallContext.GetData(TRANSACTION_KEY);
                }
            }
            set {
                if (IsInWebContext()) {
                    HttpContext.Current.Items[TRANSACTION_KEY] = value;
                }
                else {
                    CallContext.SetData(TRANSACTION_KEY, value);
                }
            }
        }

        /// <summary>
        /// If within a web context, this uses <see cref="HttpContext" /> instead of the WinForms 
        /// specific <see cref="CallContext" />.  Discussion concerning this found at 
        /// http://forum.springframework.net/showthread.php?t=572.
        /// </summary>
        private ISession ContextSession {
            get {
                if (IsInWebContext()) {
                    return (ISession)HttpContext.Current.Items[SESSION_KEY];
                }
                else {
                    return (ISession)CallContext.GetData(SESSION_KEY); 
                }
            }
            set {
                if (IsInWebContext()) {
                    HttpContext.Current.Items[SESSION_KEY] = value;
                }
                else {
                    CallContext.SetData(SESSION_KEY, value);
                }
            }
        }

        private bool IsInWebContext() {
            return HttpContext.Current != null;
        }

        private const string TRANSACTION_KEY = "CONTEXT_TRANSACTION";
        private const string SESSION_KEY = "CONTEXT_SESSION";
        private ISessionFactory sessionFactory;
    }
}

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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)


Written By
Chief Technology Officer www.Dawliasoft.com
Egypt Egypt
Program Manager in Sculpture project, Interesting in .NET Model driven development.

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