从零开始搭建前后端分离的NetCore2.2（EF Core CodeFirst+Autofac）+Vue的项目框架之二autofac解耦

在 上一篇 中将项目的基本骨架搭起来能正常跑通，这一篇将讲到，如何通过autofac将DbContext和model进行解耦，只用添加model，而不用在DbContext中添加DbSet。

在这里就不详细讲autofac是干什么用的了，简单说下autofac。

1.autofac可替换net core自带的DI IOC，用来扩展。

2.autofac可提供Aop，具体实现在博客园有很多示例。

3.autofac的几个生命周期用法：InstancePerDependency 每次都创建一个对象 ，SingleInstance 每次都是同一个对象，InstancePerLifetimeScope 同一个生命周期生成的对象是同一个。

　　接下来，我们需要在启动项目上通过nuget安装两个Package：Autofac、Autofac.Extensions.DependencyInjection。

因为autofac是通过接口来进行注入的，因此我们需要创建对应的基层接口用来注入。在basic项目通过nuget安装Autofac.Extensions.DependencyInjection、，

　　然后中添加 Dependency 文件夹来存放基层接口，添加IOC容器接口：IIocManager，代码如下：

using System;
using Autofac;
using Autofac.Core;

namespace DemoFrame_Basic.Dependency
{
    /// <summary>
    /// IOC容器接口
    /// </summary>
    public interface IIocManager
    {
        IContainer Container { get; }

        bool IsRegistered(Type serviceType, ILifetimeScope scope = null);
        object Resolve(Type type, ILifetimeScope scope = null);
        T Resolve<T>(string key = "", ILifetimeScope scope = null) where T : class;
        T Resolve<T>(params Parameter[] parameters) where T : class;
        T[] ResolveAll<T>(string key = "", ILifetimeScope scope = null);
        object ResolveOptional(Type serviceType, ILifetimeScope scope = null);
        object ResolveUnregistered(Type type, ILifetimeScope scope = null);
        T ResolveUnregistered<T>(ILifetimeScope scope = null) where T : class;
        ILifetimeScope Scope();
        bool TryResolve(Type serviceType, ILifetimeScope scope, out object instance);
    }
}

　　再添加一个数据库基础接口：IEntityBase

    /// <summary>
    /// 数据库基础接口
    /// </summary>
    public interface IEntityBase
    {
    }

　　IIocManager的实现类：IocManager

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using System.Runtime.Loader;
using Autofac;
using Autofac.Core;
using Autofac.Core.Lifetime;
using Autofac.Extensions.DependencyInjection;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.DependencyModel;

namespace DemoFrame_Basic.Dependency
{
    /// <summary>
    /// Container manager
    /// </summary>
    public class IocManager : IIocManager
    {
        private IContainer _container;

        public static IocManager Instance { get { return SingletonInstance; } }
        private static readonly IocManager SingletonInstance = new IocManager();

        /// <summary>
        /// Ioc容器初始化
        /// </summary>
        /// <param name="config"></param>
        /// <returns></returns>
        public IServiceProvider Initialize(IServiceCollection services)
        {

            //.InstancePerDependency()    //每次都创建一个对象
            //.SingleInstance()   //每次都是同一个对象
            //.InstancePerLifetimeScope()     //同一个生命周期生成的对象是同一个

            var builder = new ContainerBuilder();
            builder.RegisterInstance(Instance).As<IIocManager>().SingleInstance();
            //所有程序集 和程序集下类型
            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
            var listAllType = new List<Type>();
            foreach (var lib in libs)
            {
                try
                {
                    var assembly = AssemblyLoadContext.Default.LoadFromAssemblyName(new AssemblyName(lib.Name));
                    listAllType.AddRange(assembly.GetTypes().Where(type => type != null));
                }
                catch { }
            }

            //注册IEntityBase实现类
            var entityBaseType = typeof(IEntityBase);
            var arrEntityBaseType = listAllType.Where(t => entityBaseType.IsAssignableFrom(t) && t != entityBaseType).ToArray();
            builder.RegisterTypes(arrEntityBaseType)
                .AsImplementedInterfaces()
                .SingleInstance()
                .PropertiesAutowired();

            foreach (var type in arrEntityBaseType)
            {
                if (type.IsClass && !type.IsAbstract && !type.BaseType.IsInterface && type.BaseType != typeof(object))
                {
                    builder.RegisterType(type).As(type.BaseType)
                        .SingleInstance()
                        .PropertiesAutowired();
                }
            }


            //注册controller实现类 让Controller能被找到
            var controller = typeof(ControllerBase);
            var arrcontrollerType = listAllType.Where(t => controller.IsAssignableFrom(t) && t != controller).ToArray();
            builder.RegisterTypes(arrcontrollerType)
                .AsImplementedInterfaces()
                .SingleInstance()
                .PropertiesAutowired();

            foreach (var type in arrcontrollerType)
            {
                if (type.IsClass && !type.IsAbstract && !type.BaseType.IsInterface && type.BaseType != typeof(object))
                {
                    builder.RegisterType(type).AsSelf();
                }
            }

            builder.Populate(services);
            _container = builder.Build();
            return new AutofacServiceProvider(_container);
        }

        /// <summary>
        /// Gets a container
        /// </summary>
        public virtual IContainer Container
        {
            get
            {
                return _container;
            }
        }

        /// <summary>
        /// Resolve
        /// </summary>
        /// <typeparam name="T">Type</typeparam>
        /// <param name="key">key</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Resolved service</returns>
        public virtual T Resolve<T>(string key = "", ILifetimeScope scope = null) where T : class
        {
            if (scope == null)
            {
                //no scope specified
                scope = Scope();
            }
            if (string.IsNullOrEmpty(key))
            {
                return scope.Resolve<T>();
            }
            return scope.ResolveKeyed<T>(key);
        }

        /// <summary>
        /// Resolve
        /// </summary>
        /// <typeparam name="T">Type</typeparam>
        /// <param name="key">key</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Resolved service</returns>
        public virtual T Resolve<T>(params Parameter[] parameters) where T : class
        {
            var scope = Scope();
            return scope.Resolve<T>(parameters);
        }

        /// <summary>
        /// Resolve
        /// </summary>
        /// <param name="type">Type</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Resolved service</returns>
        public virtual object Resolve(Type type, ILifetimeScope scope = null)
        {
            if (scope == null)
            {
                //no scope specified
                scope = Scope();
            }
            return scope.Resolve(type);
        }

        /// <summary>
        /// Resolve all
        /// </summary>
        /// <typeparam name="T">Type</typeparam>
        /// <param name="key">key</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Resolved services</returns>
        public virtual T[] ResolveAll<T>(string key = "", ILifetimeScope scope = null)
        {
            if (scope == null)
            {
                //no scope specified
                scope = Scope();
            }
            if (string.IsNullOrEmpty(key))
            {
                return scope.Resolve<IEnumerable<T>>().ToArray();
            }
            return scope.ResolveKeyed<IEnumerable<T>>(key).ToArray();
        }

        /// <summary>
        /// Resolve unregistered service
        /// </summary>
        /// <typeparam name="T">Type</typeparam>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Resolved service</returns>
        public virtual T ResolveUnregistered<T>(ILifetimeScope scope = null) where T : class
        {
            return ResolveUnregistered(typeof(T), scope) as T;
        }

        /// <summary>
        /// Resolve unregistered service
        /// </summary>
        /// <param name="type">Type</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Resolved service</returns>
        public virtual object ResolveUnregistered(Type type, ILifetimeScope scope = null)
        {
            if (scope == null)
            {
                //no scope specified
                scope = Scope();
            }
            var constructors = type.GetConstructors();
            foreach (var constructor in constructors)
            {
                try
                {
                    var parameters = constructor.GetParameters();
                    var parameterInstances = new List<object>();
                    foreach (var parameter in parameters)
                    {
                        var service = Resolve(parameter.ParameterType, scope);
                        if (service == null) throw new Exception("Unknown dependency");
                        parameterInstances.Add(service);
                    }
                    return Activator.CreateInstance(type, parameterInstances.ToArray());
                }
                catch (Exception)
                {

                }
            }
            throw new Exception("No constructor  was found that had all the dependencies satisfied.");
        }

        /// <summary>
        /// Try to resolve srevice
        /// </summary>
        /// <param name="serviceType">Type</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <param name="instance">Resolved service</param>
        /// <returns>Value indicating whether service has been successfully resolved</returns>
        public virtual bool TryResolve(Type serviceType, ILifetimeScope scope, out object instance)
        {
            if (scope == null)
            {
                //no scope specified
                scope = Scope();
            }
            return scope.TryResolve(serviceType, out instance);
        }

        /// <summary>
        /// Check whether some service is registered (can be resolved)
        /// </summary>
        /// <param name="serviceType">Type</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Result</returns>
        public virtual bool IsRegistered(Type serviceType, ILifetimeScope scope = null)
        {
            if (scope == null)
            {
                //no scope specified
                scope = Scope();
            }
            return scope.IsRegistered(serviceType);
        }

        /// <summary>
        /// Resolve optional
        /// </summary>
        /// <param name="serviceType">Type</param>
        /// <param name="scope">Scope; pass null to automatically resolve the current scope</param>
        /// <returns>Resolved service</returns>
        public virtual object ResolveOptional(Type serviceType, ILifetimeScope scope = null)
        {
            if (scope == null)
            {
                //no scope specified
                scope = Scope();
            }
            return scope.ResolveOptional(serviceType);
        }

        /// <summary>
        /// Get current scope
        /// </summary>
        /// <returns>Scope</returns>
        public virtual ILifetimeScope Scope()
        {
            try
            {
                //when such lifetime scope is returned, you should be sure that it'll be disposed once used (e.g. in schedule tasks)
                return Container.BeginLifetimeScope();
            }
            catch (Exception)
            {
                //we can get an exception here if RequestLifetimeScope is already disposed
                //for example, requested in or after "Application_EndRequest" handler
                //but note that usually it should never happen

                //when such lifetime scope is returned, you should be sure that it'll be disposed once used (e.g. in schedule tasks)
                return Container.BeginLifetimeScope(MatchingScopeLifetimeTags.RequestLifetimeScopeTag);
            }
        }
    }
}

　　在这里添加完以后，我们需要将自带的DI容器给替换成现在使用的autofac，

　　在启动项目的Startup文件中更改，最终代码如下：

        public IServiceProvider ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

            services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

            services.Replace(ServiceDescriptor.Transient<IControllerActivator, ServiceBasedControllerActivator>());

            services.AddDbContext<DemoDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("SqlServerConnection")));

            return IocManager.Instance.Initialize(services);
        }

　　为了方便使用，在CoreMvc项目中添加DemoWeb的类来存放一些系统数据：

using DemoFrame_Basic.Dependency;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Hosting;
using System.Linq;

namespace DemoFrame_CoreMvc
{
    public class DemoWeb
    {
        private static IHttpContextAccessor _httpContextAccessor;

        /// <summary>
        /// Configure
        /// </summary>
        /// <param name="httpContextAccessor"></param>
        public static void Configure(IHttpContextAccessor httpContextAccessor)
        {
            _httpContextAccessor = httpContextAccessor;
        }

        /// <summary>
        /// 当前请求HttpContext
        /// </summary>
        public static HttpContext HttpContext
        {
            get => _httpContextAccessor.HttpContext;
            set => _httpContextAccessor.HttpContext = value;
        }


        /// <summary>
        /// IocManager
        /// </summary>
        public static IIocManager IocManager { get; set; }

        /// <summary>
        /// Environment
        /// </summary>
        public static IHostingEnvironment Environment { get; set; }

        /// <summary>
        /// Configuration
        /// </summary>
        public static IConfiguration Configuration { get; set; }

        /// <summary>
        /// MemoryCache
        /// </summary>
        public static IMemoryCache MemoryCache { get; set; }

        /// <summary>
        /// 获取当前请求客户端IP
        /// </summary>
        /// <returns></returns>
        public static string GetClientIp()
        {
            var ip = HttpContext.Request.Headers["X-Forwarded-For"].FirstOrDefault()?.Split(',')[0].Trim();
            if (string.IsNullOrEmpty(ip))
            {
                ip = HttpContext.Connection.RemoteIpAddress.ToString();
            }
            return ip;
        }
    }
}

　　Startup的完整代码如下：

public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            DemoWeb.Configuration = configuration;
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public IServiceProvider ConfigureServices(IServiceCollection services)
        {
            services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);

            services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();

            services.Replace(ServiceDescriptor.Transient<IControllerActivator, ServiceBasedControllerActivator>());

            services.AddDbContext<DemoDbContext>(options => options.UseSqlServer(Configuration.GetConnectionString("SqlServerConnection")));

            return IocManager.Instance.Initialize(services);
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            DemoWeb.IocManager = app.ApplicationServices.GetService<IIocManager>();
            DemoWeb.Environment = env;
            try//注意这里在本地开发允许时会重置数据库，并清空所有数据，如不需要请注释
            {
                if (env.IsDevelopment())
                {
                    using (var serviceScope = app.ApplicationServices.GetRequiredService<IServiceScopeFactory>()
                        .CreateScope())
                    {
                        var dbContent = serviceScope.ServiceProvider.GetService<DemoDbContext>();
                        //CheckMigrations(dbContent);
                        var database = serviceScope.ServiceProvider.GetService<DemoDbContext>().Database;
                        database.EnsureDeleted();
                        database.EnsureCreated();
                    }
                }
            }
            catch (Exception ex)
            {
                //LogHelper.Logger.Error(ex, "Failed to migrate or seed database");
            }
            DemoWeb.Configure(app.ApplicationServices.GetRequiredService<IHttpContextAccessor>());
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseHsts();
            }
            app.UseCors(builder => builder.AllowAnyOrigin().AllowAnyHeader().AllowAnyMethod().AllowCredentials());//允许跨域
            app.UseHttpsRedirection();
            app.UseMvc();
        }

    }

　　在这么多的配置都完成了的情况下，我们该去实现mode与DbContext的解耦操作了。那么该如何做呢？

　　废话不多说了，直接上代码，在数据库上下文DemoDbContext中将之前的DbSet删掉，更改如下：

　　！！！先将之前的model都继承 IEntityBase 接口。这样在模型生成时才能生成到数据库！！！

    /// <summary>
    /// 数据库上下文
    /// </summary>
    public class DemoDbContext : DbContext
    {
        public DemoDbContext(DbContextOptions<DemoDbContext> options)
     : base(options)
        { }

        #region IOC得到所有实体
        private readonly IEntityBase[] _entitys = DemoWeb.IocManager.ResolveAll<IEntityBase>();
        #endregion

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            if (_entitys == null)
            {
                return;
            }
            foreach (var entity in _entitys)
            {
                modelBuilder.Model.AddEntityType(entity.GetType());
            }
        }
    }

　　在使用数据库上下文是，使用Set<T>方法设置需要使用的的类

 

　　在下一篇中将介绍如何使用基类controller来统一前后端交互数据，统一使用一个模型进行返回。

 

　　有需要源码的可通过此 GitHub 链接拉取 觉得还可以的给个 start 哦，谢谢！