使用Castle Windsor在WebAPI中进行依赖注入

Question

我想使用Castle Windsor在WebApi应用程序中实现依赖注入。 我有以下示例代码 -

界面 -

public interface IWatch
{
    {
        DateTime GetTime();
    }
}

以下Watch类实现了IWatch接口 -

public class Watch:IWatch
{
        public DateTime GetTime()
        {
            return DateTime.Now;
        }
}

WebApi控制器 - WatchController如下 -

public class WatchController : ApiController
{
        private readonly IWatch _watch;

        public WatchController()
        {
            _watch = new Watch();
        }

        //http://localhost:48036/api/Watch
        public string Get()
        {
            var message = string.Format("The current time on the server is: {0}", _watch.GetTime());
            return message;
        }
}

目前我在WatchController构造函数中使用Watch启动IWatch对象。 我想删除使用Windsor Castle依赖注入原理在构造函数中初始化IWatch的依赖性。

在这种WebApi的情况下，任何人都可以为我提供实现依赖注入的步骤吗？ 提前致谢！

Answer 1

CodeCaster，Noctis和Cristiano感谢您的所有帮助和指导..我刚刚得到了上述查询的解决方案 -

第一步是使用nuget在WebApi解决方案中安装Windsor.Castle包。

请考虑以下代码段 -

接口IWatch.cs

public interface IWatch
{
     DateTime GetTime();
}

类Watch.cs

public class Watch:IWatch
{
    public DateTime GetTime()
    {
        return DateTime.Now;
    }
}

ApiController WatchController.cs的定义如下： -

public class WatchController : ApiController
{
     private readonly IWatch _watch;

     public WatchController(IWatch watch)
     {
         _watch = watch;
     }

     public string Get()
     {
         var message = string.Format("The current time on the server is: {0}", _watch.GetTime());
         return message;
     }
}

在控制器中，我们通过WatchController构造函数中的IWatch对象注入了依赖项。 我使用了IDependencyResolver和IDependencyScope来实现web api中的依赖注入。 IDependencyResolver接口用于解析请求范围之外的所有内容。

WindsorDependencyResolver.cs

internal sealed class WindsorDependencyResolver : IDependencyResolver
{
    private readonly IWindsorContainer _container;

    public WindsorDependencyResolver(IWindsorContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }

        _container = container;
    }
    public object GetService(Type t)
    {
        return _container.Kernel.HasComponent(t) ? _container.Resolve(t) : null;
    }

    public IEnumerable<object> GetServices(Type t)
    {
        return _container.ResolveAll(t).Cast<object>().ToArray();
    }

    public IDependencyScope BeginScope()
    {
        return new WindsorDependencyScope(_container);
    }

    public void Dispose()
    {

    }
}

WindsorDependencyScope.cs

internal sealed class WindsorDependencyScope : IDependencyScope
{
    private readonly IWindsorContainer _container;
    private readonly IDisposable _scope;

    public WindsorDependencyScope(IWindsorContainer container)
    {
        if (container == null)
        {
            throw new ArgumentNullException("container");
        }
        _container = container;
        _scope = container.BeginScope();
    }

    public object GetService(Type t)
    {
        return _container.Kernel.HasComponent(t) ? _container.Resolve(t) : null;
    }

    public IEnumerable<object> GetServices(Type t)
    {
        return _container.ResolveAll(t).Cast<object>().ToArray();
    }

    public void Dispose()
    {
        _scope.Dispose();
    }
}

WatchInstaller.cs

安装程序只是实现IWindsorInstaller接口的类型。 该接口有一个名为Install的方法。 该方法获取容器的实例，然后可以使用流畅的注册API注册组件：

public class WatchInstaller : IWindsorInstaller
{
      public void Install(IWindsorContainer container, IConfigurationStore store)
      {
      //Need to Register controllers explicitly in your container
      //Failing to do so Will receive Exception:

      //> An error occurred when trying to create //a controller of type
      //> 'xxxxController'. Make sure that the controller has a parameterless
      //> public constructor.

      //Reason::Basically, what happened is that you didn't register your controllers explicitly in your container. 
      //Windsor tries to resolve unregistered concrete types for you, but because it can't resolve it (caused by an error in your configuration), it return null.
      //It is forced to return null, because Web API forces it to do so due to the IDependencyResolver contract. 
      //Since Windsor returns null, Web API will try to create the controller itself, but since it doesn't have a default constructor it will throw the "Make sure that the controller has a parameterless public constructor" exception.
      //This exception message is misleading and doesn't explain the real cause.

      container.Register(Classes.FromThisAssembly()
                            .BasedOn<IHttpController>()
                            .LifestylePerWebRequest());***
          container.Register(
              Component.For<IWatch>().ImplementedBy<Watch>()
          );
      }
}

最后，我们需要使用Global.asax.cs（Application_Start方法）中的Windsor实现替换默认依赖项解析器并安装我们的依赖项：

    private static IWindsorContainer _container;
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        WebApiConfig.Register(GlobalConfiguration.Configuration);
        FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
        RouteConfig.RegisterRoutes(RouteTable.Routes);
        BundleConfig.RegisterBundles(BundleTable.Bundles);

        ConfigureWindsor(GlobalConfiguration.Configuration);
    }

    public static void ConfigureWindsor(HttpConfiguration configuration)
    {
        _container = new WindsorContainer();
        _container.Install(FromAssembly.This());
        _container.Kernel.Resolver.AddSubResolver(new CollectionResolver(_container.Kernel, true));
        var dependencyResolver = new WindsorDependencyResolver(_container);
        configuration.DependencyResolver = dependencyResolver;
    }    

Answer 2

阅读Mark Seemann关于webapi的温莎管道的文章 。

Answer 3

我没有直接与Castle Windsor合作，但我相信逻辑应该是相似的：

您的WatchController ctor应该如下所示：

public WatchController(IWatch watch) 
{
    _watch = watch;
}

这就是你inject依赖的地方。

你应该拥有一个Locator，你可以在其中注册你的WatchController类，并根据你想要的任何东西告诉它应该接收哪个手表...设计/运行时，星期几，随机数...无论什么工作或者其他什么你需要...

以下代码来自MVVM-Light，但应澄清以上段落：

static ViewModelLocator()
{
    ServiceLocator.SetLocatorProvider(() => SimpleIoc.Default);

    // This will run in design mode, so all your VS design data will come from here
    if (ViewModelBase.IsInDesignModeStatic)
    {
        SimpleIoc.Default.Register<IDataService, Design.DesignDataService>();
    }
    // This will run REAL stuff, in runtime
    else
    {
        SimpleIoc.Default.Register<IDataService, DataService>();
    }

    // You register your classes, so the framework can do the injection for you
    SimpleIoc.Default.Register<MainViewModel>();
    ...
}