Autofac3 在MVC4中的运用原理

浏览数：50 / 时间：2015年06月09日

这是一种新的开发模式，注入开发模式，或者叫它IOC模式，说起IOC你可以这样去理解它，它为你的某个实现流出一个注入点，你生产的对象，可以根据你之前的配置进行组合。 IOC全称是Inversion of Control，即反转控制,或者说是依赖注入更为合适。选择别纠结这些全称的专业词。我们可以用别外一些方式去理解它，IOC，是一种设计模式。它的延生所要实现的是把藕合从代码中移出去，统一放到XML文件中，通过一个容器在需要的时候把这个依赖关系形成，即把需要的接口实现注入到需要它的类中，这可能就是“依赖注入”说法的来源了。

而注入点的位置及方式也是多种多样的，我们今天主要说一个通过HTTP请求进行注入的方式，IOC工具使用高效的Autofac,对它的认识你可以看这篇文章。

首先看一下我们这个项目的知识点：
MVC4一个对UI层进行分层的架构模式，在微软的MVC4中加入了开源的Razor引擎
EF（Entity Framework）这无疑是微软自己比较成功的ORM（Object Relational Mapping）工具（即对象关系映射,目前数据库是关系型数据库ORM 主要是把数据库中的关系数据映射称为程序中的对象），它执行效率上要高于linq to sql，甚至你自己编写的ado.net脚本。
Autofac这是在orchard项目中被广泛的IOC工具，它支持类型，反泛，HTTP等注入
对于这个系统的autofac部分，我们将它的注入点放在controller的构造函数中，将生产的对象配置在global中，当然，你也可以设置在config文件，或者你自己的文件中。
我认为它的工作方式应该是：
网站启动=>从global中得到ioc配置信息=>http request请求页面=>通过controller中的参数进行实现的创建=>action中使用创建好的对象

OK，有了这样一个理论基础，我们来看一下代码吧：

EF部分的DATA层

  1  public partial class EfRepository<T> : IRepository<T> where T : class  2     {
  3         private readonly Guid _instanceId;
  4         private readonly IDbContext _context;
  5         private IDbSet<T> _entities;
  6         public Guid InstanceId
  7         {
  8             get { return _instanceId; }
  9         }
 10         public EfRepository(IDbContext context)
 11         {
 12             AutoCommitEnabled = true;
 13             this._context = context;
 14             _instanceId = Guid.NewGuid();
 15         }
 16         public T GetById(object id)
 17         {
 18             return this._entities.Find(id);
 19         }
 20         public T Create()
 21         {
 22             return this.Entities.Create();
 23         }
 24         public void Insert(T entity)
 25         {
 26             try
 27             {
 28                 if (entity == null)
 29                     throw new ArgumentNullException("entity");
 30                 this.Entities.Add(entity);
 31                 if (this.AutoCommitEnabled)
 32                     _context.SaveChanges();
 33             }
 34             catch(DbEntityValidationException dbEx)
 35             {
 36                 var msg = string.Empty;
 37                 foreach(var validationErrors in dbEx.EntityValidationErrors)
 38                     foreach (var validationError in validationErrors.ValidationErrors)
 39                         msg += string.Format("Property: {0} Error: {1}", validationError.PropertyName, validationError.ErrorMessage) + Environment.NewLine;
 40                 var fail = new Exception(msg, dbEx);
 41                 throw fail;
 42             }
 43         }
 44 
 45         public void InsertRange(IEnumerable<T> entities, int batchSize = 100)
 46         {
 47             try
 48             {
 49                 if (entities == null)
 50                     throw new ArgumentNullException("entities");
 51                 if (entities.HasItems())
 52                 {
 53                     if (batchSize <= 0)
 54                     {
 55                         entities.Each(x => this.Entities.Add(x));
 56                         if (this.AutoCommitEnabled)
 57                             _context.SaveChanges();
 58                     }
 59                     else
 60                     {
 61                         int i = 1;
 62                         bool saved = false;
 63                         foreach (var entity in entities)
 64                         {
 65                             this.Entities.Add(entity);
 66                             saved = false;
 67                             if (i % batchSize == 0)
 68                             {
 69                                 if (this.AutoCommitEnabled)
 70                                     _context.SaveChanges();
 71                                 i = 0;
 72                                 saved = true;
 73                             }
 74                             i++;
 75                         }
 76                         if (!saved)
 77                         {
 78                             if (this.AutoCommitEnabled)
 79                                 _context.SaveChanges();
 80                         }
 81                     }
 82                 }
 83             }
 84             catch (DbEntityValidationException ex)
 85             {
 86                 throw ex;
 87             }
 88         }
 89         public void Update(T entity)
 90         {
 91             if (entity == null)
 92                 throw new ArgumentNullException("entity");
 93             try
 94             {
 95                 if (this.InternalContext.Entry(entity).State == EntityState.Detached)
 96                 {
 97                     var set = Entities;
 98                     T attachedEntity = set.Find(entity.Key);  // You need to have access to key
 99 
100                     if (attachedEntity != null)
101                     {
102                         var attachedEntry = this.InternalContext.Entry(attachedEntity);
103                         attachedEntry.CurrentValues.SetValues(entity);
104                     }
105                     else
106                     {
107                         // This should attach entity
108                         this.InternalContext.Entry(entity).State = EntityState.Modified;
109                     }
110                 }
111             }
112             finally { }
113 
114             if (AutoCommitEnabled)
115                 _context.SaveChanges();
116         }
117 
118         public void Delete(T entity)
119         {
120             if (entity == null)
121                 throw new ArgumentNullException("entity");
122             if(InternalContext.Entry(entity).State==EntityState.Detached)
123             {
124                 this.Entities.Attach(entity);
125             }
126             this.Entities.Remove(entity);
127             if (this.AutoCommitEnabled)
128                 _context.SaveChanges();
129         }
130 
131         public IDictionary<string, object> GetModifiedProperties(T entity)
132         {
133             var props = new Dictionary<string, object>();
134 
135             var ctx = InternalContext;
136             var entry = ctx.Entry(entity);
137             var modifiedPropertyNames = from p in entry.CurrentValues.PropertyNames
138                                         where entry.Property(p).IsModified
139                                         select p;
140             foreach (var name in modifiedPropertyNames)
141             {
142                 props.Add(name, entry.Property(name).OriginalValue);
143             }
144 
145             return props;
146         }
147         public virtual IQueryable<T> Table
148         {
149             get
150             {
151                 return this.Entities;
152             }
153         }
154 
155         public int Commit()
156         {
157             try
158             {
159                 return this._context.SaveChanges();
160             }
161             catch(DbEntityValidationException dbEx)
162             {
163                 var msg = string.Empty;
164                 foreach (var validationErrors in dbEx.EntityValidationErrors)
165                     foreach (var validationError in validationErrors.ValidationErrors)
166                         msg += Environment.NewLine + string.Format("Property: {0} Error: {1}", validationError.PropertyName, validationError.ErrorMessage);
167 
168                 var fail = new Exception(msg, dbEx);
169                 throw fail;
170             }
171         }
172         #region Helpers
173         protected internal dwDbContextBase InternalContext
174         {
175             get { return _context as dwDbContextBase; }
176         }
177         public bool AutoCommitEnabled { get; set; }
178 
179         private DbSet<T> Entities
180         {
181             get
182             {
183                 if (_entities == null) { _entities = _context.Set<T>(); }
184                 return _entities as DbSet<T>;
185             }
186         }
187 
188         #endregion
189 
190         public IQueryable<T> Include(IQueryable<T> query,string path)
191         {
192             Guard.ArgumentNotNull(query, "query");
193             Guard.ArgumentNotEmpty(path, "path");
194             return query.Include(path);
195         }
196         public IQueryable<T> Include<TProperty>(IQueryable<T> query,Expression<Func<T,TProperty>> path)
197         {
198             Guard.ArgumentNotNull(query, "query");
199             Guard.ArgumentNotNull(path, "path");
200             return query.Include(path);
201         }
202         public IDbContext Context
203         {
204             get { return _context; }
205         }
206 
207     }

Services层（BLL层）核心代码：

 1   public class TestService : BaseService, ITestService
 2     {
 3         private const string IncludeProperties = "";
 4         private readonly IRepository<Tests> _repository;
 5         private readonly ICacheManager _cacheManager;
 6         private readonly IExporter _exporter;
 7         public IList<Tests> GetAll()
 8         {
 9             return _repository.FindBy(null, null, IncludeProperties).ToList();
10         }
11 
12         public TestService(IRepository<Tests> repository,
13             ICacheManager cacheManager,IExporter exporter,
14             IEventPublisher eventPublisher):base(eventPublisher)
15         {
16             _repository = repository;
17             _exporter = exporter;
18             _cacheManager = cacheManager;
19         }
20 
21     }

WEB层MVC部分代码：(注意：我们的WEB层不应该有对DATA层的引用，WEB层一般只注入SERVICE的对象，这一点是需要注意的，即不要直接调用数据库仓库）

 public class TestController : ApiController
    {
        private readonly ITestService _service;
        private readonly Func<Tests, TestsModel, TestsModel> _convertCallback = (entity, model) => { return model; };
        public TestController(ITestService service) { _service = service; }
        public IEnumerable<TestsModel> Get()
        {
            var items = _service.GetAll();
            var model = items.ConvertTo(_convertCallback);
            return model;
        }

而注入参数我们放在global中，看一下核心代码：

            //初始化依赖注入组件
            var bootStrapper = new AutofacBootStrapper();
            BootStrapperManager.Initialize(bootStrapper);
            //设置依赖注入
            GlobalConfiguration.Configuration.DependencyResolver = bootStrapper.GetWebApiDependencyResolver();
            DependencyResolver.SetResolver(bootStrapper.GetMvcDependencyResolver());

 builder.Register(c => new dwObjectContext("MyConnection")).As<IDbContext>().InstancePerHttpRequest().InstancePerApiRequest();
            builder.RegisterGeneric(typeof(EfRepository<>)).As(typeof(IRepository<>)).InstancePerHttpRequest().InstancePerApiRequest();

            //注册缓存类型
            builder.RegisterType<StaticCache>().As<ICache>().Named<ICache>(YB_CACHE_STATIC).SingleInstance();
            builder.RegisterType<RequestCache>().As<ICache>().Named<ICache>(YB_CACHE_PER_REQUEST).InstancePerHttpRequest().InstancePerApiRequest();
            //注册缓存控制类型
            builder.RegisterType<NullCacheManager>()
                .As<ICacheManager>()
                .Named<ICacheManager>(YB_SM_CACHE_NULL)
                .WithParameter(ResolvedParameter.ForNamed<ICache>(YB_CACHE_STATIC))
                .SingleInstance();

            builder.RegisterType<DefaultCacheManager>()
                .As<ICacheManager>()
                .Named<ICacheManager>(YB_SM_CACHE_PER_REQUEST)
                .WithParameter(ResolvedParameter.ForNamed<ICache>(YB_CACHE_PER_REQUEST))
                .InstancePerHttpRequest().InstancePerApiRequest();

            builder.RegisterType<DefaultCacheManager>()
               .As<ICacheManager>()
                //.Named<ICacheManager>(YB_SM_CACHE_STATIC)
               .WithParameter(ResolvedParameter.ForNamed<ICache>(YB_CACHE_STATIC))
               .SingleInstance();

            var assembly = Assembly.GetExecutingAssembly();
            //注册所有 MVC 控制器
            builder.RegisterControllers(assembly)
                .InstancePerHttpRequest();
            //注册所有 Web Api 控制器
            builder.RegisterApiControllers(assembly)
                .InstancePerApiRequest();