NHibernate Session-per-request and MiniProfiler.NHibernate
前言
1、本文以mvc3为例，借鉴开源项目 NerdDnner项目完成nhibernate中的 Session-per-request 模式，本文创建了一个自定义的httpmodel类，来实现在http请求的时候创建并开启一个session并绑定到CurrentSessionContext中，当请求完成以后关闭，同时包含对事物的处理。
2、利用MiniProfiler.NHibernate来追踪项目中的产生的sql，便于我们及时发现问题及时处理。MiniProfiler.NHibernate现在可以在nuget上直接获取或者可以去github中下载源码查看。
实现Session per request
public class NHibernateSessionPerRequest : IHttpModule { private static readonly ISessionFactory sessionFactory; //构造函数 static NHibernateSessionPerRequest() { sessionFactory = CreateSessionFactory(); } // 初始化httpmodel public void Init( HttpApplication context ) { context.BeginRequest += BeginRequest; context.EndRequest += EndRequest; } public void Dispose() { } public static ISession GetCurrentSession() { return sessionFactory.GetCurrentSession(); } // 打开session, 开启事务, 绑定session到CurrentSessionContext private static void BeginRequest( object sender, EventArgs e ) { ISession session = sessionFactory.OpenSession(); session.BeginTransaction(); CurrentSessionContext.Bind( session ); } // 移除session会话, 事物提交, and 关闭session会话 private static void EndRequest( object sender, EventArgs e ) { ISession session = CurrentSessionContext.Unbind( sessionFactory ); if ( session == null ) return; try { session.Transaction.Commit(); } catch ( Exception ) { session.Transaction.Rollback(); } finally { session.Close(); session.Dispose(); } } // 创建sessionfactory private static ISessionFactory CreateSessionFactory() { return Fluently.Configure(new Configuration().Configure()) .Mappings( m => m.AutoMappings.Add( CreateMappings() ) ) .ExposeConfiguration( UpdateSchema ) .CurrentSessionContext<WebSessionContext>() .BuildSessionFactory(); } private static AutoPersistenceModel CreateMappings() { return AutoMap .Assembly( System.Reflection.Assembly.GetCallingAssembly() ) .Where( t => t.Namespace != null && t.Namespace.EndsWith( "Models" ) ) .Conventions.Setup( c => c.Add( DefaultCascade.SaveUpdate() ) ); } // 生成数据库架构 private static void UpdateSchema( Configuration cfg ) { new SchemaUpdate( cfg ) .Execute( false, true ); } }
此类的nh的配置采用fluent的方式配置映射，可以生成数据库架构，ISessionFactory在每次请求中只会生成一次，当我们需要session的时候只需调用GetCurrentSession方法，当http请求的时候session创建并存储在CurrentSessionContext.Bind()中，并开启事物操作，当请求结束的时候 CurrentSessionContext.Unbind()移除session，事物提交并将session关闭。这里存在一些问题：尽管session是非常轻量级的，这样每一次http请求都会去创建session，并不能做到我们真正需要的时候去创建。
注册httpmodel：
在web.config中添加如下2处节点：
测试程序
Models：
public class Employee { public virtual int Id { get; protected set; } public virtual string FirstName { get; set; } public virtual string LastName { get; set; } public virtual Store Store { get; set; } } public class Product { public virtual int Id { get; protected set; } public virtual string Name { get; set; } public virtual double Price { get; set; } public virtual IList<Store> StoresStockedIn { get; protected set; } public Product() { StoresStockedIn = new List<Store>(); } } public class Store { public virtual int Id { get; protected set; } public virtual string Name { get; set; } public virtual IList<Product> Products { get; protected set; } public virtual IList<Employee> Staff { get; protected set; } public Store() { Products = new List<Product>(); Staff = new List<Employee>(); } public virtual void AddProduct( Product product ) { product.StoresStockedIn.Add( this ); Products.Add( product ); } public virtual void AddEmployee( Employee employee ) { employee.Store = this; Staff.Add( employee ); } }
Repositories:
public interface IRepository<T> { IQueryable<T> GetAll(); IQueryable<T> Get( Expression<Func<T, bool>> predicate ); IEnumerable<T> SaveOrUpdateAll( params T[] entities ); T SaveOrUpdate( T entity ); } public class Repository<T> : IRepository<T> { private readonly ISession session; public Repository() { session = NHibernateSessionPerRequest.GetCurrentSession(); } public IQueryable<T> GetAll() { return session.Query<T>(); } public IQueryable<T> Get( Expression<Func<T, bool>> predicate ) { return GetAll().Where( predicate ); } public IEnumerable<T> SaveOrUpdateAll( params T[] entities ) { foreach ( var entity in entities ) { session.SaveOrUpdate( entity ); } return entities; } public T SaveOrUpdate( T entity ) { session.SaveOrUpdate( entity ); return entity; } }
HomeController：
public class HomeController : Controller { private readonly IRepository<Store> storeRepository; public HomeController() { storeRepository = new Repository<Store>(); } public ActionResult Index() { var stores = storeRepository.GetAll(); return View(stores.ToList()); } public ActionResult Test() { var barginBasin = storeRepository.Get(s => s.Name == "Bargin Basin").SingleOrDefault(); if (barginBasin == null) { return RedirectToAction("Index"); } barginBasin.Name = "Bargain Basin"; return RedirectToAction("Index"); } public ActionResult Seed() { var barginBasin = new Store { Name = "Bargin Basin" }; var superMart = new Store { Name = "SuperMart" }; var potatoes = new Product { Name = "Potatoes", Price = 3.60 }; var fish = new Product { Name = "Fish", Price = 4.49 }; var milk = new Product { Name = "Milk", Price = 0.79 }; var bread = new Product { Name = "Bread", Price = 1.29 }; var cheese = new Product { Name = "Cheese", Price = 2.10 }; var waffles = new Product { Name = "Waffles", Price = 2.41 }; var daisy = new Employee { FirstName = "Daisy", LastName = "Harrison" }; var jack = new Employee { FirstName = "Jack", LastName = "Torrance" }; var sue = new Employee { FirstName = "Sue", LastName = "Walkters" }; var bill = new Employee { FirstName = "Bill", LastName = "Taft" }; var joan = new Employee { FirstName = "Joan", LastName = "Pope" }; AddProductsToStore(barginBasin, potatoes, fish, milk, bread, cheese); AddProductsToStore(superMart, bread, cheese, waffles); AddEmployeesToStore(barginBasin, daisy, jack, sue); AddEmployeesToStore(superMart, bill, joan); storeRepository.SaveOrUpdateAll(barginBasin, superMart); return RedirectToAction("Index"); } private void AddProductsToStore(Store store, params Product[] products) { foreach (var product in products) { store.AddProduct(product); } } private void AddEmployeesToStore(Store store, params Employee[] employees) { foreach (var employee in employees) { store.AddEmployee(employee); } } }
完成以后，修改hibernate.cfg.xml中的链接字符串等，并将其属性复制到输出目录修改为：如果较新则复制，运行程序请求index方法，将会产生数据库架构。
配置MiniProfiler.NHibernate
1、使用nuget控制台Install-Package MiniProfiler.NHibernate安装，或者参考github中的代码自己写一个
2、修改NH配置文件中的数据库驱动类，将connection.driver_class几点替换为
<property name="connection.driver_class"> StackExchange.Profiling.NHibernate.Drivers.MiniProfilerSql2008ClientDriver,StackExchange.Profiling.NHibernate </property>
3、在模板页中中的<head>节点添加@MiniProfiler.RenderIncludes()方法调用，修改Global.asax，添加如下代码：
protected void Application_BeginRequest() { if (Request.IsLocal) { MiniProfiler.Start(); } } /// <summary> /// 终止时结束 /// </summary> protected void Application_EndRequest() { MiniProfiler.Stop(); }
配置完成后运行程序，便可以看到MiniProfiler.NHibernate的效果了，使用它可以帮我们监控nh产生的sql及时优化代码，举个例子，运行请求home/seed的测试数据方法，看看追踪的效果
文章结束，时间仓促代码粗略，文中若有不合理的地方，欢迎批评指正。
