为ASP.NET MVC创建一个基于Unity的ControllerFactory

谈到IoC和ASP.NET的集成，很多人会先后想到Ninject，不过我们个人还是倾向于Unity。这篇文章简单地介绍如果创建基于Unity的ControllerFactory。如下面的代码所示，我们通过直接继承DefaultControllerFactory创建一个自定的UnityControllerFactory。构造函数指定的是配置的UnityContainer的名称，如果没有显式指定则采用默认的UnityContainer。在重写的GetControllerInstance方法中，直接调用IUnityContainer的Resolve方法根据Controller类型创建相应的对象。[源代码从这里下载]

public class UnityControllerFactory: DefaultControllerFactory
{
    public IUnityContainer Container { get; private set; }
    public UnityControllerFactory(string containerName = "")
    {
        IUnityContainer container = new UnityContainer();
        UnityConfigurationSection configSection = ConfigurationManager.GetSection(UnityConfigurationSection.SectionName) as UnityConfigurationSection;
        if (null == configSection && !string.IsNullOrEmpty(containerName))
        {
            throw new ConfigurationErrorsException("Cannot find <unity> configuration section");
        }

        if (string.IsNullOrEmpty(containerName))
        {
            configSection.Configure(container);
        }
        else
        {
            configSection.Configure(container, containerName);
        }
        this.Container = container;
    }
    protected override IController GetControllerInstance(RequestContext requestContext, Type controllerType)
    {
        Guard.ArgumentNotNull(controllerType, "controllerType");
        return (IController)this.Container.Resolve(controllerType);
    }
}

为了演示DefaultControllerFactory的作用，我们来创建一个简单的例子。假设我们要创建一个维护联系人的应用，我们通过具有如下定义的Contact类型表示联系人，而IContactRepository接口定义了一个从存储中获取所有联系人的GetAllContacts方法，DefaultContactRepository是对IContactRepository接口的实现。

public class Contact
{
    public string Name { get; set; }
    public string Gender { get; set; }
    public string Address { get; set; }
}

public interface IContactRepository
{
    IEnumerable<Contact> GetAllContacts();
}

public class DefaultContactRepository : IContactRepository
{
    public IEnumerable<Contact> GetAllContacts()
    {
        yield return new Contact
        {
            Name = "Zhang San",
            Gender = "Male",
            Address = "#328, XingHu Street, Su Zhou, Jiang Su Province, PRC."
        };

        yield return new Contact
        {
            Name = "Li Si",
            Gender = "Female",
            Address = "#328, Jin Ji Hu Road, Su Zhou, Jiang Su Province, PRC."
        };
    }
}

我们在Web应用的主页显示联系人列表，为此我创建了如下一个HomeController。在这里我们演示的是构造器注入，所以我们通过构造函数指定的IContactRepository对象来初始化Repository属性。在Action方法Index中调用IContactRepository的GetAllContacts方法为对应的View指定Model。

public class HomeController : Controller
{
    public IContactRepository Repository { get; private set; }
    public HomeController(IContactRepository repository)
    {
        this.Repository = repository;
    }
    public ActionResult Index()
    {
        return View(this.Repository.GetAllContacts());
    }
}

Index.cshtml代码如下所示，这是一个Model类型为IEnumerable<Contact>的View，它将所有的联系人信息列出来。

@model IEnumerable<Artech.Web.Mvc.Extensions.Contact>
@{
    ViewBag.Title = "Index";
}

<h2>Contact List</h2>

<div>
<ul>
@foreach (var contact in this.Model)
{
    <li>
        <h3>@contact.Name</h3>
        <p>Gender: @contact.Gender</p>
        <p>Address: @contact.Address</p>
        <hr />
    </li>
}
</ul>
</div>

自定义的UnityContainerFactory的注册定义在Gloable.asax中。初次之外，额外需要做的是忽略掉针对favicon.ico的路由，否则程序运行将会失败。

public class MvcApplication : System.Web.HttpApplication
{
    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
    {
        filters.Add(new HandleErrorAttribute());
    }

    public static void RegisterRoutes(RouteCollection routes)
    {
        routes.IgnoreRoute("favicon.ico");
        routes.IgnoreRoute("{resource}.axd/{*pathInfo}");
        routes.MapRoute("Default", "{controller}/{action}/{id}",
            new { controller = "Home", action = "Index", id = UrlParameter.Optional }
        );
    }

    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();
        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);

        ControllerBuilder.Current.SetControllerFactory(new UnityControllerFactory());
    }
}

接口IContactRepository和DefualtContactRepository之间的映射关系定义在如下所示的<unity>配置中。

<unity>
  <alias alias="IContactRepository" type="Artech.Web.Mvc.Extensions.IContactRepository, UnityIntegration" />
  <alias alias="DefaultContactRepository" type="Artech.Web.Mvc.Extensions.DefaultContactRepository, UnityIntegration" />
  <container>
    <register type="IContactRepository" mapTo="DefaultContactRepository"/>
  </container>
</unity>

通过浏览器访问Web应用的主页，将会得到如下所示的联系人列表。