我想为我的ASP.Net 5.0 / MVC 6应用程序创建一个Plugin Enviroment。我使用Autofac作为IOC容器，我喜欢从DNX LibraryManager中的构建加载插件（类库）。使用图书馆经理的目的是，我不必关心NuGet包和框架。
我遇到的问题是LifeCycle，我必须在LibraryManager的实例可用之前构建IOC容器。因为Autofac容器提供了他自己的IServiceProvider实例，我必须在ConfigureService（）方法调用（AddAutofac）中注入。
有谁知道如何使这个工作？
更新：我已经修复了戴维斯帮助的问题，并更新了代码以使其与候选版本一起使用。我也增加了对配置的支持。
在我的DNX类库中，我实现了一个自我注册类：
public class AutofacModule : Module
{
protected override void Load(ContainerBuilder builder)
{
builder.Register(c => new SimpleService())
.As<IService>()
.InstancePerLifetimeScope();
}
}
在我的MVC WebApplication中，我已将类库添加为依赖项。
Startup.cs
public IConfiguration Configuration { get; set; }
public class Startup
{
public Startup( IApplicationEnvironment applicationEnvironment )
{
IConfigurationBuilder configurationBuilder = new ConfigurationBuilder();
configurationBuilder.SetBasePath( applicationEnvironment.ApplicationBasePath );
configurationBuilder.AddJsonFile( "appsettings.json" );
configurationBuilder.AddJsonFile( "autofac.json" );
configurationBuilder.AddEnvironmentVariables();
this.Configuration = configurationBuilder.Build();
}
public void ConfigureServices(IServiceCollection services)
{
services.AddMvc();
services.AddDependencies();
}
public void Configure(IApplicationBuilder applicationBuilder, IHostingEnvironment hostingEnvironment)
{
applicationBuilder.UseDependencies( this.Configuration );
applicationBuilder.UseStaticFiles();
applicationBuilder.UseMvc();
}
}
我创建了一个DependencyResolver来保存ContainerBuilder实例。
DependencyResolver.cs
public class DependencyResolver : IDependencyResolver
{
private IContainer container;
private readonly ContainerBuilder builder;
public DependencyResolver()
{
this.builder = new ContainerBuilder();
}
public void RegisterModule( IModule module )
{
this.builder.RegisterModule( module );
}
public void RegisterModules( IEnumerable<Assembly> assemblies )
{
this.builder.RegisterAssemblyModules(assemblies.ToArray());
}
public void Populate( IServiceCollection services)
{
this.builder.Populate( services );
}
public void Build()
{
this.container = this.builder.Build();
}
public T Resolve<T>() where T : class
{
return this.container?.Resolve<T>();
}
}
IDependencyResolver.cs
public interface IDependencyResolver
{
void RegisterModule( IModule module );
void RegisterModules( IEnumerable<Assembly> assemblies );
void Populate(IServiceCollection services);
void Build();
T Resolve<T>() where T : class;
}
最后但并非最不重要的是，我创建了一个扩展类
DependencyResolverExtensions.cs
public static class DependencyResolverExtensions
{
public static IServiceCollection AddDependencies( this IServiceCollection services )
{
DependencyResolver dependencyResolver = new DependencyResolver();
dependencyResolver.Populate(services);
ServiceDescriptor serviceDescriptor = new ServiceDescriptor(typeof ( IDependencyResolver ), dependencyResolver );
services.TryAdd(serviceDescriptor);
return services;
}
public static IApplicationBuilder UseDependencies(this IApplicationBuilder applicationBuilder, IConfiguration configuration)
{
IDependencyResolver dependencyResolver = applicationBuilder.GetService<IDependencyResolver>();
if (dependencyResolver == null) return applicationBuilder;
ILibraryManager libraryManager = applicationBuilder.GetService<ILibraryManager>();
if (libraryManager == null) return applicationBuilder;
IEnumerable<Assembly> assemblies = libraryManager.GetLoadableAssemblies();
dependencyResolver.RegisterModules(assemblies);
ConfigurationModule configurationModule = new ConfigurationModule( configuration );
dependencyResolver.RegisterModule( configurationModule );
dependencyResolver.Build();
IServiceProvider serviceProvider = dependencyResolver.Resolve<IServiceProvider>();
applicationBuilder.ApplicationServices = serviceProvider;
return applicationBuilder;
}
public static IEnumerable<Assembly> GetLoadableAssemblies(this ILibraryManager libraryManager)
{
List<Assembly> result = new List<Assembly>();
IEnumerable<Library> libraries = libraryManager.GetLibraries();
IEnumerable<AssemblyName> assemblyNames = libraries.SelectMany(e => e.Assemblies).Distinct();
assemblyNames = Enumerable.Where(assemblyNames, e => e.Name.StartsWith("MyLib."));
foreach (AssemblyName assemblyName in assemblyNames)
{
Assembly assembly = Assembly.Load(assemblyName);
result.Add(assembly);
}
return result;
}
public static T GetService<T>(this IApplicationBuilder applicationBuilder) where T : class
{
return applicationBuilder.ApplicationServices.GetService(typeof (T)) as T;
}
}
如果您需要在不同的实现之间切换，例如模拟和实际数据，您可以使用Autofac配置。
autofac.json
{
"components": [
{
"type": "MyLib.Data.EF.EntitiesData, MyLib.Data.EF",
"services": [
{
"type": "MyLib.Abstractions.IDataRepository, MyLib.Abstractions"
}
]
}
]
}
答案 0 :(得分：3)
令人遗憾的是，ConfigureServices不可注入，这将使这更容易。
查看代码，您应该可以安全地替换IServiceProvider而不是Configure(...)内的ConfigureServices(...)并获得预期的行为。 ApplicationServices is setable
在UseAutofac方法中，您应该可以执行以下操作：
public static IApplicationBuilder UseAutofac( [NotNull] this IApplicationBuilder applicationBuilder )
{
IAutofacResolver autofacResolver = applicationBuilder.GetService<IAutofacResolver>();
ILibraryManager libraryManager = applicationBuilder.GetService<ILibraryManager>();
autofacResolver.RegisterLibraryModules( libraryManager);
applicationBuilder.ApplicationServices = autofacResolver.Resolve();
return applicationBuilder;
}
答案 1 :(得分：1)
我提出了一个使用其中一部分的解决方案，但也使用了一个ComponentContainer来解决DependencyResolver中潜在的内存泄漏问题。这也适用于RC1。还不确定RC2，因为它不足以让我测试。
ComponentContainer如下所示：
public static class ComponentContainer {
static IContainer _container;
static ContainerBuilder _containerBuilder;
public static ContainerBuilder Builder {
get {
if (_containerBuilder == null)
_containerBuilder = new ContainerBuilder();
return _containerBuilder;
}
}
public static IServiceProvider ServiceProvider {
get {
if (_container == null)
_container = _containerBuilder.Build();
return _container.Resolve<IServiceProvider>();
}
}
public static ComponentFactory<TObject> Component<TObject>() => new ComponentFactory<TObject>(_container);
public static void RegisterAssembly(Assembly assembly) {
if (assembly == null) return;
foreach (var obj in assembly.GetTypes().Where(t => t.GetCustomAttribute<ExportAttribute>() != null)) {
ExportAttribute att = obj.GetCustomAttribute<ExportAttribute>();
if (att.ContractType != null) {
_containerBuilder.RegisterType(obj).As(att.ContractType);
} else {
foreach (var intf in obj.GetInterfaces())
_containerBuilder.RegisterType(obj).As(intf);
}
}
}
}
public class ComponentFactory<TObject> : IDisposable {
protected TObject CurrentObject;
protected ILifetimeScope CurrentScope;
public TObject Current => (TObject)CurrentObject;
public ComponentFactory(IContainer container) {
CurrentScope = container.BeginLifetimeScope();
CurrentObject = CurrentScope.Resolve<TObject>();
}
public TObject Component => CurrentObject;
public void Dispose() {
(CurrentObject as IDisposable)?.Dispose();
CurrentScope.Dispose();
}
}
然后在Startup.cs中我执行以下操作：
public virtual IServiceProvider ConfigureServices(IServiceCollection services) {
services.AddMvc();
services.AddOptions();
services.AddSession();
services.AddCaching();
var assemblyLoadContextAccessor = services.FirstOrDefault(s => s.ServiceType == typeof(IAssemblyLoadContextAccessor)).ImplementationInstance as IAssemblyLoadContextAccessor;
var libraryManager = services.FirstOrDefault(s => s.ServiceType == typeof(ILibraryManager)).ImplementationInstance as ILibraryManager;
var loadContext = assemblyLoadContextAccessor.Default;
foreach(var library in libraryManager.GetLibraries()) {
var assembly = loadContext.Load(library.Name);
if(assembly != null) {
var module = assembly.GetTypes().FirstOrDefault(t => t == typeof(IModule));
if(module != null)
ComponentContainer.Builder.RegisterAssemblyModules(assembly);
else
ComponentContainer.RegisterAssembly(assembly);
}
}
ComponentContainer.Builder.Populate(services);
return ComponentContainer.ServiceProvider;
}
要导出程序集中的模块，我要么用ExportAttribute标记它们，要么在实现Autofac的IModule的程序集中添加一个类。 ConfigureServices中的代码将枚举应用程序的模块，并将它们提供给ComponentContainer中的静态构建器。构建容器后，您可以通过构造函数中的注入来解析模块，也可以通过以下方式请求特定类型：
(using var myComponentFactory = ComponentContainer.Component<IMyModule>()) {
//You can now access your component through myComponentFactory.Component
//Once it passes out of scope of using, it will be properly disposed of
//along with the scope from which it was created.
}
编辑：随着RC2的发布，此代码不再有效，因为程序集和类的枚举将失败。我还没有想出一个好的解决方案。如果其他人有任何关于在RC2中枚举程序集的建议，请告诉我。