一个NHibernate应用的实际例子(A good open source project to learn how to use NHibernate)

此项目名字叫Cuyahoga,是一个CMS。该项目中就使用了NHibernate0.6作为持久层。并且使用了NHibernate0.6新添加的Lazy loading特性,是学习使用NHibernate的上佳例子。
下面是对他的一些评价
- Use the HttpContext to store your NHibernate session facade. This is what I call the HttpContext Local Session pattern 8-)  
 使用HttpContext .Item来存储NH的Session,亦即使用了HttpRequest--Session的模式

- Access to the session facade is provided by a property get in your overrided ASP.NET page's base class, such as "base.GetCoreRepository.LoadObjectById(..)". This is an alternative to having the repository itself control instantiation such as "CoreRepository.Instance.LoadObjectById(..)"  
 CoreRepository就是一个数据访问逻辑组件了,对Session进行了管理,并且提供数据持久化的方法。部分代码如下:

    public class CoreRepository
    
{
        
private ISessionFactory _factory;
        
private ISession _activeSession;

        
/// <summary>
        
/// Get the active NHibernate session.
        
/// </summary>

        public ISession ActiveSession
        
{
            
get return this._activeSession; }
        }

        
/// <summary>
        
/// Create a repository for core objects.
        
/// </summary>

        public CoreRepository() : this(false)
        
{
        }


        
/// <summary>
        
/// Create a repository for core objects.
        
/// </summary>
        
/// <param name="openSession">Indicate if the CoreRepository should open a session and keep it in memory.</param>

        public CoreRepository(bool openSession)
        
{
            
this._factory = SessionFactory.GetInstance().GetNHibernateFactory();
            
if (openSession)
            
{
                
this._activeSession = this._factory.OpenSession();
            }

        }


        
/// <summary>
        
/// Open a NHibernate session.
        
/// </summary>

        public void OpenSession()
        
{
            
if (this._activeSession == null || ! this._activeSession.IsOpen)
            
{
                
this._activeSession = this._factory.OpenSession();
            }

            
else
            
{
                
throw new InvalidOperationException("The repository already has an open session");
            }

        }


        
/// <summary>
        
/// Flushes the current active NHibernate session.
        
/// </summary>

        public void FlushSession()
        
{
            
if (this._activeSession != null && this._activeSession.IsOpen)
            
{
                
this._activeSession.Flush();
            }

        }


        
/// <summary>
        
/// Close the active NHibernate session
        
/// </summary>

        public void CloseSession()
        
{
            
if (this._activeSession != null && this._activeSession.IsOpen)
            
{
                
this._activeSession.Close();
            }

        }


        
Generic methods
           }


- A new NHibernate Open Session at beginning of a web request and close it at the end of the request. This is the "session-per-request" pattern. 
- Using a custom IHttpModule called NHSessionModule to provide the handlers for Context_BeginRequest and Context_EndRequest. This is a nice way of automatically wiring up your creation/opening and closing and sessions. 
 使用了一个HttpModule 来进行Session的存储和获得,代码如下:

using System;
using System.Web;
using Cuyahoga.Core.Service;

namespace Cuyahoga.Web.Util
{
    
在一个HTTP Request期间管理NHibetnate的Session
}


也就是将session保存到HttpContext.Current.Items中,这样做的好处请看这里

NHibernate中添加的最重要的特性就是用proxy对延迟加载的支持(包括对集合的和单个object的延迟加载),这也是因为项目中使用了动态代理技术(这要求业务实体的成员需要是virtual的或者实现某个接口), 这为多表的join带来了性能上的提升。

posted @ 2005-01-12 17:29  风满袖  阅读(...)  评论(...编辑  收藏