【懒人有道】在asp.net core中实现程序集注入

前言

在asp.net core中，我巨硬引入了DI容器，我们可以在不使用第三方插件的情况下轻松实现依赖注入。如下代码：

         // This method gets called by the runtime. Use this method to add services to the container.
         public void ConfigureServices(IServiceCollection services)
         {
             //services.RegisterAssembly("IServices");
             services.AddSingleton<IUserService, UserService>();
             // Add framework services.
             services.AddMvc();
             services.AddMvcCore()
                 .AddApiExplorer();
             services.AddSwaggerGen(options =>
             {
                 options.SwaggerDoc("v1", new Info()
                 {
                     Title = "Swagger测试",
                     Version = "v1",
                     Description = "Swagger测试RESTful API ",
                     TermsOfService = "None",
                     Contact = new Contact
                     {
                         Name = "来来吹牛逼",
                         Email = "xxoo123@outlook.com"
                     },
                 });
                 //设置xml注释文档，注意名称一定要与项目名称相同
                 var filePath = Path.Combine(PlatformServices.Default.Application.ApplicationBasePath, "WebApi.xml");
                 options.IncludeXmlComments(filePath);
             });
         }

但是，随着公司业务的扩大，系统项目的功能模块急剧扩张，新增了不下百个或者千个Repository和Service（有点夸张了...），这时候如此单纯滴注入就有点操蛋了。

打懒主意

我可不可以通过反射技术来实现对程序集的注入呢？？

试试就试试

首先，我私自先制定一些类名的约束。规则嘛，反正是自己定。比如：

• UserService --> IUserService
• UserRepository --> IUserRepository
• ......
• ClassName --> IClassName

好了，我们下面开始编码：

     /// <summary>
     /// IServiceCollection扩展
     /// </summary>
     public static class ServiceExtension
     {
         /// <summary>
         /// 用DI批量注入接口程序集中对应的实现类。
         /// <para>
         /// 需要注意的是，这里有如下约定：
         /// IUserService --> UserService, IUserRepository --> UserRepository.
         /// </para>
         /// </summary>
         /// <param name="service"></param>
         /// <param name="interfaceAssemblyName">接口程序集的名称（不包含文件扩展名）</param>
         /// <returns></returns>
         public static IServiceCollection RegisterAssembly(this IServiceCollection service, string interfaceAssemblyName)
         {
             if (service == null)
                 throw new ArgumentNullException(nameof(service));
             if (string.IsNullOrEmpty(interfaceAssemblyName))
                 throw new ArgumentNullException(nameof(interfaceAssemblyName));

             var assembly = RuntimeHelper.GetAssembly(interfaceAssemblyName);
             if (assembly == null)
             {
                 throw new DllNotFoundException($"the dll \"{interfaceAssemblyName}\" not be found");
             }

             //过滤掉非接口及泛型接口
             var types = assembly.GetTypes().Where(t => t.GetTypeInfo().IsInterface && !t.GetTypeInfo().IsGenericType);

             foreach (var type in types)
             {
                 var implementTypeName = type.Name.Substring();
                 var implementType = RuntimeHelper.GetImplementType(implementTypeName, type);
                 if (implementType != null)
                     service.AddSingleton(type, implementType);
             }
             return service;
         }

         /// <summary>
         /// 用DI批量注入接口程序集中对应的实现类。
         /// </summary>
         /// <param name="service"></param>
         /// <param name="interfaceAssemblyName">接口程序集的名称（不包含文件扩展名）</param>
         /// <param name="implementAssemblyName">实现程序集的名称（不包含文件扩展名）</param>
         /// <returns></returns>
         public static IServiceCollection RegisterAssembly(this IServiceCollection service, string interfaceAssemblyName, string implementAssemblyName)
         {
             if (service == null)
                 throw new ArgumentNullException(nameof(service));
             if(string.IsNullOrEmpty(interfaceAssemblyName))
                 throw new ArgumentNullException(nameof(interfaceAssemblyName));
             if (string.IsNullOrEmpty(implementAssemblyName))
                 throw new ArgumentNullException(nameof(implementAssemblyName));

             var interfaceAssembly = RuntimeHelper.GetAssembly(interfaceAssemblyName);
             if (interfaceAssembly == null)
             {
                 throw new DllNotFoundException($"the dll \"{interfaceAssemblyName}\" not be found");
             }

             var implementAssembly = RuntimeHelper.GetAssembly(implementAssemblyName);
             if (implementAssembly == null)
             {
                 throw new DllNotFoundException($"the dll \"{implementAssemblyName}\" not be found");
             }

             //过滤掉非接口及泛型接口
             var types = interfaceAssembly.GetTypes().Where(t => t.GetTypeInfo().IsInterface && !t.GetTypeInfo().IsGenericType);

             foreach (var type in types)
             {
                 //过滤掉抽象类、泛型类以及非class
                 var implementType = implementAssembly.DefinedTypes
                     .FirstOrDefault(t => t.IsClass && !t.IsAbstract && !t.IsGenericType &&
                                          t.GetInterfaces().Any(b => b.Name == type.Name));
                 if (implementType != null)
                 {
                     service.AddSingleton(type, implementType.AsType());
                 }
             }

             return service;
         }
     }

附上RuntimeHelper.cs的代码：

     public class RuntimeHelper
     {
         /// <summary>
         /// 获取项目程序集，排除所有的系统程序集(Microsoft.***、System.***等)、Nuget下载包
         /// </summary>
         /// <returns></returns>
         public static IList<Assembly> GetAllAssemblies()
         {
             var list = new List<Assembly>();
             var deps = DependencyContext.Default;
             var libs = deps.CompileLibraries.Where(lib => !lib.Serviceable && lib.Type != "package");//排除所有的系统程序集、Nuget下载包
             foreach (var lib in libs)
             {
                 try
                 {
                     var assembly = AssemblyLoadContext.Default.LoadFromAssemblyName(new AssemblyName(lib.Name));
                     list.Add(assembly);
                 }
                 catch (Exception)
                 {
                     // ignored
                 }
             }
             return list;
         }

         public static Assembly GetAssembly(string assemblyName)
         {
             return GetAllAssemblies().FirstOrDefault(assembly => assembly.FullName.Contains(assemblyName));
         }

         public static IList<Type> GetAllTypes()
         {
             var list = new List<Type>();
             foreach (var assembly in GetAllAssemblies())
             {
                 var typeInfos = assembly.DefinedTypes;
                 foreach (var typeInfo in typeInfos)
                 {
                     list.Add(typeInfo.AsType());
                 }
             }
             return list;
         }

         public static IList<Type> GetTypesByAssembly(string assemblyName)
         {
             var list = new List<Type>();
             var assembly = AssemblyLoadContext.Default.LoadFromAssemblyName(new AssemblyName(assemblyName));
             var typeInfos = assembly.DefinedTypes;
             foreach (var typeInfo in typeInfos)
             {
                 list.Add(typeInfo.AsType());
             }
             return list;
         }

         public static Type GetImplementType(string typeName, Type baseInterfaceType)
         {
             return GetAllTypes().FirstOrDefault(t =>
             {
                 if (t.Name == typeName &&
                     t.GetTypeInfo().GetInterfaces().Any(b => b.Name == baseInterfaceType.Name))
                 {
                     var typeInfo = t.GetTypeInfo();
                     return typeInfo.IsClass && !typeInfo.IsAbstract && !typeInfo.IsGenericType;
                 }
                 return false;
             });
         }
     }

好了，到此就基本完成了，记得在Startup.cs加上：

 // This method gets called by the runtime. Use this method to add services to the container.
         public IServiceProvider ConfigureServices(IServiceCollection services)
         {
             services.RegisterAssembly("IServices");

             // Add framework services.
             services.AddMvc();
         }

总结

小记一下，好记性不如烂笔头。