实现WCF和Unity 的集成

Artech 已经写过一篇[原创]WCF后续之旅（7）：通过WCF Extension实现和Enterprise Library Unity Container的集成，在这个解决方案中Unity的侵入性有点强，本文介绍一种具有更少的侵入性的解决方案。

第一步：创建一个自定义的InstanceProvider 来处理WCF服务。

InstanceProvider就是用于创建或者提供service instance的。除了提供service instance的创建者或者提供者的身份外，InstanceProvider还用于service instance的释放和回收。所有的IntanceProvider实现了System.ServiceModel.Dispatcher.IInstanceProvider 接口：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Practices.Unity;
using System.ServiceModel.Dispatcher;
using System.ServiceModel;
using System.ServiceModel.Channels;

namespace Tencent.OA.Framework.ServiceModel
{
    public class UnityInstanceProvider : IInstanceProvider
    {

        public UnityContainer Container { set; get; }
        public Type ServiceType { set; get; }

        public UnityInstanceProvider()
            : this(null)
        {

        }

        public UnityInstanceProvider(Type type)
        {

            ServiceType = type;
            Container = new UnityContainer();

        }

        #region IInstanceProvider Members

        public object GetInstance(InstanceContext instanceContext, Message message)
        {
            return Container.Resolve(ServiceType);
        }

        public object GetInstance(InstanceContext instanceContext)
        {
            return GetInstance(instanceContext, null);
        }

        public void ReleaseInstance(InstanceContext instanceContext, object instance)
        {

        }

        #endregion

    }
}

可以看到GetInstance方法用来获取服务实例，通过Unity的Resolve方法解析。

第二步：创建UnityInstanceProvider对应的Behavior

第一步已经创建了自定义的UnityInstanceProvider，现在需要在运行时插入我们这个新的Provider，这项工作可以通过IServiceProvider（定义一种检索服务对象的机制，服务对象是为其他对象提供自定义支持的对象）来完成。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel.Dispatcher;
using System.ServiceModel.Description;
using System.ServiceModel;
using System.Collections.ObjectModel;
using System.ServiceModel.Channels;
using Microsoft.Practices.Unity;

namespace Tencent.OA.Framework.ServiceModel
{
    public class UnityServiceBehavior : IServiceBehavior
    {

        public UnityInstanceProvider InstanceProvider

        { get; set; }

        private ServiceHost serviceHost = null;

        public UnityServiceBehavior()
        {

            InstanceProvider = new UnityInstanceProvider();

        }

        public UnityServiceBehavior(UnityContainer unity)
        {
            InstanceProvider = new UnityInstanceProvider();
            InstanceProvider.Container = unity;

        }

        public void ApplyDispatchBehavior(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
        {

            foreach (ChannelDispatcherBase cdb in serviceHostBase.ChannelDispatchers)
            {

                ChannelDispatcher cd = cdb as ChannelDispatcher;

                if (cd != null)
                {

                    foreach (EndpointDispatcher ed in cd.Endpoints)
                    {
                        InstanceProvider.ServiceType = serviceDescription.ServiceType;
                        ed.DispatchRuntime.InstanceProvider = InstanceProvider;
                    }

                }

            }

        }

        public void Validate(ServiceDescription serviceDescription, ServiceHostBase serviceHostBase)
        { }

        public void AddBindingParameters(ServiceDescription serviceDescription,ServiceHostBase serviceHostBase,Collection<ServiceEndpoint> endpoints,
            BindingParameterCollection bindingParameters)
        {

        }

    }

}

当调用ApplyDispatchBehaviour，代码通过循环收集在我们的项目Endpoints，并传递给相应的服务类型的InstanceProvider。

第三步：创建自定义的增加新的Behavior的 Service Host

ServiceHost 提供了基本的“加载服务，配置endpoints，应用安全设置以及启动监听请求”机制。通过自定义一个ServiceHost将我们自己的Behavior添加进去。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ServiceModel;
using Microsoft.Practices.Unity;

namespace Tencent.OA.Framework.ServiceModel
{
    public class UnityServiceHost : ServiceHost
    {

        public UnityContainer Container { set; get; }

        public UnityServiceHost()
            : base()
        {
            Container = new UnityContainer();
        }

        public UnityServiceHost(Type serviceType, params Uri[] baseAddresses)
            : base(serviceType, baseAddresses)
        {

            Container = new UnityContainer();

        }

        protected override void OnOpening()
        {

            if (this.Description.Behaviors.Find<UnityServiceBehavior>() == null)
                this.Description.Behaviors.Add(new UnityServiceBehavior(Container));

            base.OnOpening();
        }

    }

}

当Service Host启动的时候，它就会检查我们的UnityServiceBehavior是否已经添加到Behaviors里面，如果没有就把它加入到Behaviors集合。

第四步：创建自定义的ServiceHostFactory

如果只是承载在Console Application、Windows Service或者其他非Web应用程序，我们的工作已经完成了。但在Web的.svc中，ServiceHost是动态创建的，没有显示的指定ServiceHost的Factory,那它在默认情况下是使用ServiceHostFactory的，而ServiceHostFactory产生的是ServiceHost对象，想要使用我们上一步中自定义的UnityServiceHost ，需要实现一个自定义的ServcieHostFactory,实现代码非常简单：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Practices.Unity.Configuration;
using Microsoft.Practices.Unity;
using System.ServiceModel.Activation;
using System.ServiceModel;
using System.Configuration;

namespace Tencent.OA.Framework.ServiceModel
{
    public class UnityServiceHostFactory : ServiceHostFactory
    {

        protected override ServiceHost CreateServiceHost(

                                    Type serviceType, Uri[] baseAddresses)
        {

            UnityServiceHost serviceHost = new UnityServiceHost(serviceType, baseAddresses);
            UnityContainer container = new UnityContainer();
            serviceHost.Container = container;
            //configure container
            UnityConfigurationSection section = (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
            section.Containers.Default.Configure(serviceHost.Container);
            return serviceHost;

        }

    }

}