Web项目下NHibernate的Session管理的解决方案 【转】

NHibernate的Session的管理一直是个问题，在系统开发中

如果有lazy="true"，如果不对Session进行管理，会抛出以下错误：

CODE:

Failed to lazily initialize a collection - no session

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在Web项目下的解决方案，就是在Application_BeginRequest方法中打开Session并放入HttpContext，在Application_EndRequest方法中关闭Sesssion就可以了。

还好，NHibernate1.2已经提供了相关的支持，如下：

在web.config中加入以下代码

CODE:

<httpModules>
<add name="CurrentSessionModule" type="NHibernate.Example.Web.CurrentSessionModule" />
</httpModules>

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程序如下：

CODE:

using System;
using System.Web;
using NHibernate.Context;

namespace NHibernate.Example.Web
{
public class CurrentSessionModule : IHttpModule
{
public void Init(HttpApplication context)
{
context.BeginRequest += new EventHandler(Application_BeginRequest);
context.EndRequest += new EventHandler(Application_EndRequest);
}

public void Dispose()
{
}

private void Application_BeginRequest(object sender, EventArgs e)
{
ManagedWebSessionContext.Bind(HttpContext.Current, ExampleApplication.SessionFactory.OpenSession());
}

private void Application_EndRequest(object sender, EventArgs e)
{
ISession session = ManagedWebSessionContext.Unbind(HttpContext.Current, ExampleApplication.SessionFactory);
if(session !=null)
{
if (session.Transaction.IsActive)
{
session.Transaction.Rollback();
}

if (session != null)
{
session.Close();
}
}
}
}
}
====================================================================
另外我在Codesmith中也找到了一个关于session管理的模版,请看代码

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

using NHibernate;
using NHibernate.Cfg;

namespace NHibernate.Generated.Base
{
public interface INHibernateSessionManager : IDisposable
{
// Methods
INHibernateSession CreateSession();
ISession CreateISession();

// Properties
INHibernateSession Session { get; }
}

/// <summary>
/// A Singleton that creates and persits a single SessionFactory for the to program to access globally.
/// This uses the .Net CallContext to store a session for each thread.
///
/// This is heavely based on 'NHibernate Best Practices with ASP.NET' By Billy McCafferty.
/// http://www.codeproject.com/KB/architecture/NHibernateBestPractices.aspx
/// </summary>
public class NHibernateSessionManager : INHibernateSessionManager
{
#region Static Content

private static INHibernateSessionManager _nHibernateSessionManager = null;
/// <summary>
/// Set method is exposed so that the INHibernateSessionManager can be swapped out for Unit Testing.
/// NOTE: Cannot set Instance after it has been initialized, and calling Get will automatically intialize the Instance.
/// </summary>
public static INHibernateSessionManager Instance
{
get
{
if(_nHibernateSessionManager == null)
_nHibernateSessionManager = new NHibernateSessionManager();
return _nHibernateSessionManager;
}
set
{
if (_nHibernateSessionManager != null)
throw new Exception("Cannot set Instance after it has been initialized.");
_nHibernateSessionManager = value;
}
}

#endregion

#region Declarations

private ISessionFactory _sessionFactory = null;
private const string _sessionContextKey = "NHibernateSession-ContextKey";

#endregion

#region Constructors & Finalizers

/// <summary>
/// This will load the NHibernate settings from the App.config.
/// Note: This can/should be expanded to support multiple databases.
/// </summary>
private NHibernateSessionManager()
{
_sessionFactory = new NHibernate.Cfg.Configuration().Configure().BuildSessionFactory();
}
~NHibernateSessionManager()
{
Dispose(true);
}

#endregion

#region IDisposable

private bool _isDisposed = false;
public void Dispose()
{
Dispose(false);
}
private void Dispose(bool finalizing)
{
if (!_isDisposed)
{
// Close SessionFactory
_sessionFactory.Close();
_sessionFactory.Dispose();

// Flag as disposed.
_isDisposed = true;
if (!finalizing)
GC.SuppressFinalize(this);
}
}

#endregion

#region Methods

public INHibernateSession CreateSession()
{
return new NHibernateSession(CreateISession());
}
public ISession CreateISession()
{
ISession iSession;
lock (_sessionFactory)
{
iSession = _sessionFactory.OpenSession();
}
return iSession;
}

#endregion

#region Properties

public INHibernateSession Session
{
get
{
INHibernateSession session = ContextSession;

// If the thread does not yet have a session, create one.
if (session == null)
{
session = CreateSession();

// Save to CallContext.
ContextSession = session;
}

return session;
}
}
private INHibernateSession ContextSession
{
get
{
if (IsWebContext)
return (NHibernateSession)System.Web.HttpContext.Current.Items[_sessionContextKey];
else
return (NHibernateSession)System.Runtime.Remoting.Messaging.CallContext.GetData(_sessionContextKey);
}
set
{
if (IsWebContext)
System.Web.HttpContext.Current.Items[_sessionContextKey] = value;
else
System.Runtime.Remoting.Messaging.CallContext.SetData(_sessionContextKey, value);
}
}
private bool IsWebContext
{
get { return (System.Web.HttpContext.Current != null); }
}

#endregion
}
}