自定义Unity对象生命周期管理集成ADO.NET Entity Framework

2022-06-14 02:12:37

在Unity中，从Unity 取得的实例为 Transient。如果你希望使用多线程方式，就需要在组成时使用lifecycle参数，这时候取出的组件就不再是同一个了。在Unity IOC中，它支持我们对于组件的实例进行控制，也就是说我们可以透明的管理一个组件拥有多少个实例。Unity IOC容器提供了如下几种生命处理方式：
# Singleton：一个组件只有一个实例被创建，所有请求的客户使用程序得到的都是同一个实例。
# Transient：这种处理方式与我们平时使用new的效果是一样的，对于每次的请求得到的都是一个新的实例。
# Custom：自定义的生命处理方式。

我要增加一个Request的，一个Request请求一个实例，然后在Request结束的时候，回收资源。增加一个Resquest级别的LifetimeManager，HttpContext.Items中数据是Request期间共享数据用的，所以HttpContext.Items中放一个字典，用类型为key，类型的实例为value。如果当前Context.Items中有类型的实例，就直接返回实例。 ObjectContext本身是有缓存的，整个Request内都是一个ObjectContext，ObjectContext一级缓存能力进一步利用。

用在Unity中，如何获取对象的实例及如何销毁对象都是由LifetimeManager完成的，其定义如下
public abstract class LifetimeManager : ILifetimePolicy, IBuilderPolicy
{
protected LifetimeManager();

    public abstract object GetValue();
    public abstract void RemoveValue();
    public abstract void SetValue(object newValue);
}

其中GetValue方法获取对象实例，RemoveValue方法销毁对象，SetValue方法为对外引用的保存提供新的实例

有了这3个方法，就可以通过自定义LifetimeManager来实现从HttpContext中取值。

下面我们来实现Unity集成ADO.NET Entity Framework的工作：

1、利用Unity的依赖注入，ObjectContext会给我们生成3个构造函数，类似于下面的代码：

// Original file name:
// Generation date: 2008/8/24 10:05:33
namespace RequestLifeTimeManagerTest
{
using Microsoft.Practices.Unity;

    /// <summary>
    /// There are no comments for AdventureWorksLTEntities in the schema.
    /// </summary>
    public partial class AdventureWorksLTEntities : global::System.Data.Objects.ObjectContext
    {
        /// <summary>
        /// Initializes a new AdventureWorksLTEntities object using the connection string found in the 'AdventureWorksLTEntities' section of the application configuration file.
        /// </summary>
        public AdventureWorksLTEntities() :
                base("name=AdventureWorksLTEntities", "AdventureWorksLTEntities")
        {
            this.OnContextCreated();
        }
        /// <summary>
        /// Initialize a new AdventureWorksLTEntities object.
        /// </summary>
        public AdventureWorksLTEntities(string connectionString) :
                base(connectionString, "AdventureWorksLTEntities")
        {
            this.OnContextCreated();
        }
        /// <summary>
        /// Initialize a new AdventureWorksLTEntities object.
        /// </summary>
        public AdventureWorksLTEntities(global::System.Data.EntityClient.EntityConnection connection) :
                base(connection, "AdventureWorksLTEntities")
        {
            this.OnContextCreated();
        }
        partial void OnContextCreated();

……

}

构造函数注入包含了二种情况，一种是类仅有一个构造函数时，Unity 可以进行自动注入；另一种情况是，类包含多个构造函数时，必须使用 Attribute 或者配置文件指定注入时使用的构造函数。

ObjectContext有多个构造函数，而且ObjectContext的构造函数代码是Visual Studio 代码生成的，最好的选择是使用配置文件或者使用配置API指定注入时使用的构造函数。下面是使用配置API：

namespace RequestLifeTimeManagerTest
{
    public class EFContainerExtension : UnityContainerExtension
    {
        protected override void Initialize()
        {
           this.Container.RegisterType<AdventureWorksLTEntities, AdventureWorksLTEntities>(new RequestControlledLifetimeManager(typeof(AdventureWorksLTEntities)))
                .Configure<InjectedMembers>()
                    .ConfigureInjectionFor<AdventureWorksLTEntities>(new InjectionConstructor());
        }
    }
}

我们定义了一个Unity扩展，在扩展类EFContainerExtension 我们选择了第一个构造函数以及ObjectContext使用RequestControlledLifetimeManager实现ObjectContext的生命周期管理。

2、实现RequestControlledLifetimeManager，完成对整个Request内都是一个ObjectContext的对象的生命周期管理：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using Microsoft.Practices.Unity;

namespace RequestLifeTimeManagerTest
{
    public class RequestControlledLifetimeManager : LifetimeManager
    {
        private Type objectType;

        /// <summary>
        ///
        /// </summary>
        /// <param name="t"></param>
        public RequestControlledLifetimeManager(Type t)
        {
            this.objectType = t;
        }

        private IDictionary<Type, object> GetObjectTable()
        {
            IDictionary<Type, object> objects = HttpContext.Current.Items[RequestLifeTimeManagerTest.UnityHttpModule.UNITYOBJECTS]
                as IDictionary<Type, object>;
            if (objects == null)
            {
                lock (this)
                {
                    if (HttpContext.Current.Items[RequestLifeTimeManagerTest.UnityHttpModule.UNITYOBJECTS] == null)
                    {
                        objects = new Dictionary<Type, object>();
                        HttpContext.Current.Items[RequestLifeTimeManagerTest.UnityHttpModule.UNITYOBJECTS] = objects;
                    }
                    else
                    {
                        return HttpContext.Current.Items[RequestLifeTimeManagerTest.UnityHttpModule.UNITYOBJECTS]
                            as IDictionary<Type, object>;
                    }
                }
            }
            return objects;
        }

        public override object GetValue()
        {
            IDictionary<Type, object> objects = this.GetObjectTable();
            object obj = null;
            if (objects.TryGetValue(this.objectType, out obj))
            {
                return obj;
            }
            return null;
        }

        public override void RemoveValue()
        {
            IDictionary<Type, object> objects = this.GetObjectTable();
            object obj = null;
            if (objects.TryGetValue(this.objectType, out obj))
            {
                ((IDisposable)obj).Dispose();
                objects.Remove(this.objectType);
            }
        }

        public override void SetValue(object newValue)
        {
            IDictionary<Type, object> objects = this.GetObjectTable();
            objects.Add(this.objectType, newValue);
        }
    }
}

写一个HttpMoudle,在Request结束的时候回收资源。

using System;
using System.Web;
using System.Collections.Generic;

namespace RequestLifeTimeManagerTest
{
    public class UnityHttpModule : IHttpModule
    {
        internal const string UNITYOBJECTS = "UNITYOBJECTS";
        #region IHttpModule Members

        public void Dispose()
        {
            //clean-up code here.
        }

        public void Init(HttpApplication context)
        {
            context.EndRequest += new EventHandler(context_EndRequest);

}

#endregion

        private void context_EndRequest(object sender, EventArgs e)
        {
            IDictionary<Type, object> objects = HttpContext.Current.Items[UNITYOBJECTS]
                as IDictionary<Type, object>;
            if (objects != null)
            {
                foreach (Type key in objects.Keys)
                {
                    if (objects[key] is IDisposable)
                    {
                        ((IDisposable)objects[key]).Dispose();
                    }
                }
                HttpContext.Current.Items.Remove(UNITYOBJECTS);
            }
        }

}
}

3、web.config中的配置文件内容如下，注意看红色部分：

<?xml version="1.0"?>
<configuration>
    <configSections>
        <sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
            <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
                <section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" />
                <sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35">
                    <section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="Everywhere" />
                    <section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" />
                    <section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" />
                    <section name="roleService" type="System.Web.Configuration.ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" />
                </sectionGroup>
            </sectionGroup>
        </sectionGroup>
        <section name="unity" type="Microsoft.Practices.Unity.Configuration.UnityConfigurationSection, Microsoft.Practices.Unity.Configuration" />
    </configSections>
    <unity>
        <typeAliases>
      <typeAlias alias="string" type="System.String, mscorlib" />
            <typeAlias alias="singleton" type="Microsoft.Practices.Unity.ContainerControlledLifetimeManager, Microsoft.Practices.Unity" />
            <typeAlias alias="transient" type="Microsoft.Practices.Unity.TransientLifetimeManager, Microsoft.Practices.Unity" />
    </typeAliases>
        <containers>
            <container>
        <types>
          <type type="RequestLifeTimeManagerTest.Gateways.IProductGateway,RequestLifeTimeManagerTest" mapTo="RequestLifeTimeManagerTest.Gateways.ProductGateway, RequestLifeTimeManagerTest">
          </type>
        </types>
        <extensions>
          <add type="RequestLifeTimeManagerTest.EFContainerExtension, RequestLifeTimeManagerTest" />
        </extensions>
            </container>
        </containers>
    </unity>
    <appSettings />
    <connectionStrings><add name="AdventureWorksLTEntities" connectionString="metadata=res://*/AdventureWorksModel.csdl|res://*/AdventureWorksModel.ssdl|res://*/AdventureWorksModel.msl;provider=System.Data.SqlClient;provider connection string="Data Source=GEFF-PC;Initial Catalog=AdventureWorksLT;Integrated Security=True;MultipleActiveResultSets=True"" providerName="System.Data.EntityClient" /></connectionStrings>
    <system.web>
        
        <compilation debug="true">
            <assemblies>
                <add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
                <add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
                <add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" />
                <add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" />
            <add assembly="System.Data.Entity, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" /></assemblies>
        </compilation>
        
        <authentication mode="Windows" />
        <!--
            The <customErrors> section enables configuration
            of what to do if/when an unhandled error occurs
            during the execution of a request. Specifically,
            it enables developers to configure html error pages
            to be displayed in place of a error stack trace.

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