【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(1);
                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。