如何将MEF与ASP.NET MVC 4和ASP.NET Web API集成-Java 学习之路

如何在同一个项目中将Managed Extensibility Framework（MEF）与ASP.NET MVC 4和ASP.NET Web API集成？

考虑一个示例应用程序，其中包含MVC控制器 HomeController 和Web API控制器 ContactController . 两者都具有 IContactRepository 类型的属性，它们依赖于MEF来解析 . 问题是如何将MEF插入MVC和Web API，以便通过MEF创建实例 .

HomeController:

/// <summary>
/// Home controller. Instruct MEF to create one instance of this class per importer,
/// since this is what MVC expects.
/// </summary>
[Export]
[PartCreationPolicy(CreationPolicy.NonShared)]
public class HomeController : Controller
{
    [Import]
    private IContactRepository _contactRepository = null;

    public ActionResult Index()
    {
        return View(_contactRepository.GetAllContacts());
    }
}

ContactController:

/// <summary>
/// Contact API controller. Instruct MEF to create one instance of this class per importer,
/// since this is what Web API expects.
/// </summary>
[Export]
[PartCreationPolicy(CreationPolicy.NonShared)]
public class ContactController : ApiController
{
    [Import]
    private IContactRepository _contactRepo = null;

    public Contact[] Get()
    {
        return _contactRepo.GetAllContacts();
    }
}

IContactRepository and ContactRepository:

public interface IContactRepository
{
    Contact[] GetAllContacts();
}

[Export(typeof(IContactRepository))]
public class ContactRepository : IContactRepository
{
    public Contact[] GetAllContacts()
    {
        return new Contact[] {
            new Contact { Id = 1, Name = "Glenn Beck"},
            new Contact { Id = 2, Name = "Bill O'Riley"}
        };
    }
}

Contact:

public class Contact
{
    public int Id { get; set; }
    public string Name { get; set; }
}

6 回答

解决方案是实现System.Web.Mvc.IDependencyResolver和System.Web.Http.Dependencies.IDependencyResolver，并在 Application_Start 方法中分别使用ASP.NET MVC和ASP.NET Web API注册实现 .

在这个例子中，我们将创建一个类 MefConfig ，它实现了一个从 Application_Start 调用的方法 RegisterMef ，以便安装我们的依赖项解析器 . 类 MefDependencyResolver 实现 System.Web.Mvc.IDependencyResolver 和 System.Web.Http.Dependencies.IDependencyResolver ，因此，处理MVC和Web API的依赖项解析任务 .

Application_Start, Put This in Your Global.asax.cs:

public class WebApiApplication : System.Web.HttpApplication
{
    protected void Application_Start()
    {
        [...]
        MefConfig.RegisterMef();
    }
}

MefDependencyResolver and MefConfig:

/// <summary>
/// Resolve dependencies for MVC / Web API using MEF.
/// </summary>
public class MefDependencyResolver : System.Web.Http.Dependencies.IDependencyResolver, System.Web.Mvc.IDependencyResolver
{
    private readonly CompositionContainer _container;

    public MefDependencyResolver(CompositionContainer container)
    {
        _container = container;
    }

    public IDependencyScope BeginScope()
    {
        return this;
    }

    /// <summary>
    /// Called to request a service implementation.
    /// 
    /// Here we call upon MEF to instantiate implementations of dependencies.
    /// </summary>
    /// <param name="serviceType">Type of service requested.</param>
    /// <returns>Service implementation or null.</returns>
    public object GetService(Type serviceType)
    {
        if (serviceType == null)
            throw new ArgumentNullException("serviceType");

        var name = AttributedModelServices.GetContractName(serviceType);
        var export = _container.GetExportedValueOrDefault<object>(name);
        return export;
    }

    /// <summary>
    /// Called to request service implementations.
    /// 
    /// Here we call upon MEF to instantiate implementations of dependencies.
    /// </summary>
    /// <param name="serviceType">Type of service requested.</param>
    /// <returns>Service implementations.</returns>
    public IEnumerable<object> GetServices(Type serviceType)
    {
        if (serviceType == null)
            throw new ArgumentNullException("serviceType");

        var exports = _container.GetExportedValues<object>(AttributedModelServices.GetContractName(serviceType));
        return exports;
    }

    public void Dispose()
    {
    }
}

public static class MefConfig
{
    public static void RegisterMef()
    {
        var asmCatalog = new AssemblyCatalog(Assembly.GetExecutingAssembly());
        var container = new CompositionContainer(asmCatalog);
        var resolver = new MefDependencyResolver(container);
        // Install MEF dependency resolver for MVC
        DependencyResolver.SetResolver(resolver);
        // Install MEF dependency resolver for Web API
        System.Web.Http.GlobalConfiguration.Configuration.DependencyResolver = resolver;
    }
}

回复于 2024-05-02T20:39:21+08:00

1

你可以看一下这个http://kennytordeur.blogspot.be/2012/08/mef-in-aspnet-mvc-4-and-webapi.html . 它解释了如何在Asp.net MVC 4 / Web Api项目中使用MEF . 基于此代码也存在Nuget package . 这样您就可以非常轻松快速地进行测试 .

回复于 2024-05-02T20:39:21+08:00

@ aknuds1答案是我迄今为止看到的将MEF集成到DependencyResolver中的最佳答案 . 我能够相当容易地扩展它以在MEF2中使用基于约定的组合 . MefConfig类是改变所需的所有内容，而不是更多 .

/// <summary>
///     Responsible for configuring MEF for the application.
/// </summary>
public static class MefConfig
{
    /// <summary>
    ///     Registers MEF conventions and exports.
    /// </summary>
    public static void RegisterMef()
    {
        // Register MVC/API conventions
        var registrationBuilder = new RegistrationBuilder();
        registrationBuilder.ForTypesDerivedFrom<Controller>().SetCreationPolicy(CreationPolicy.NonShared).Export();
        registrationBuilder.ForTypesDerivedFrom<ApiController>().SetCreationPolicy(CreationPolicy.NonShared).Export();
        var assemblyCatalog = new AssemblyCatalog(Assembly.GetExecutingAssembly(), registrationBuilder);
        var aggregateCatalog = new AggregateCatalog(assemblyCatalog);
        var container = new CompositionContainer(aggregateCatalog);
        var resolver = new MefDependencyResolver(container);
        // Install MEF dependency resolver for MVC
        DependencyResolver.SetResolver(resolver);
        // Install MEF dependency resolver for Web API
        GlobalConfiguration.Configuration.DependencyResolver = resolver;
    }
}

回复于 2024-05-02T20:39:21+08:00

0

Kenny Torduer先生的解决方案对我有用，而假设的正确答案却没有（虽然所有相关部分都在catelog中，但我无法解析控制器实例，但我得到了“类型没有默认构造函数”错误）！

Correction ：两种方法实际上都有效，我在公约部分注册表中的一个基本错误是愚蠢的 . 我真诚地向作者提供了正确的答案 .

回复于 2024-05-02T20:39:21+08:00

这是我在MVC4项目中使用的一种更简单的方法 .

public static class MefConfig
{
     public static CompositionContainer MefContainer = null;

     public static void Initialise()
     {
          AggregateCatalog cat = new AggregateCatalog();
          cat.Catalogs.Add(new AssemblyCatalog(Assembly.GetExecutingAssembly()));
          MefContainer = new CompositionContainer(cat);
      }
}

public class MefFilterAttribute : ActionFilterAttribute
{
   public override void OnActionExecuting(ActionExecutingContext filterContext)
   {
      MefConfig.MefContainer.ComposeParts(filterContext.Controller);
   }        
}

在Application_Start中运行MefConfig.Initialise（）并在FilterConfig.RegisterGlobalFilters（GlobalFilterCollection过滤器）中输入filters.Add（new Filters.MefFilterAttribute（））;

回复于 2024-05-02T20:39:21+08:00

我关注@ akanuds1的答案，但我还必须将ControllerFactory更改为：

public class MefControllerFactory : DefaultControllerFactory
{
    private readonly CompositionContainer compositionContainer;

    public MefControllerFactory(CompositionContainer compositionContainer)
    {
        this.compositionContainer = compositionContainer;
    }

    protected override IController GetControllerInstance(System.Web.Routing.RequestContext requestContext, Type controllerType)
    {
        var export = compositionContainer.GetExports(controllerType, null, null).SingleOrDefault();

        IController result;

        if (null != export)
        {
            result = export.Value as IController;
        }
        else
        {
            result = base.GetControllerInstance(requestContext, controllerType);
            compositionContainer.ComposeParts(result);
        }

        return result;
    }
}

Glogal.asax.cs

protected void Application_Start()
{
    ...
    var container = MefConfig.Register();
    ControllerBuilder.Current.SetControllerFactory(new MefControllerFactory(container));
}

回复于 2024-05-02T20:39:21+08:00

如何将MEF与ASP.NET MVC 4和ASP.NET Web API集成

6 回答

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