Architecture & Pattern & Practise 之 我也IoC

对于IoC，第一次接触这个概念在当初学Spring的时候，当时觉得这种设计真是合理，使用IoC我们就能将我们创建的对象管理起来，而不必在对象间手动传来传去还要自己维护。使用Spring更能增强我们对denpendency relation的理解。

Ioc英文为 Inversion of Control，即反转模式，后被大牛Martin Fowler改名为 Dependency Injection 依赖注入，就是将组件之间的关系通过第三方进行注射，不需要类自己在代码中去使用Get/Set解决调用关系。

今天我们模拟写一个IoC。通过配置文件来进行组件注册。

先看看流行的.NET下几种优秀IoC

Castle：（官方站点http://www.castleproject.org/）

说明	不使用配置文件，容器使用的是一个第三方的组件：Windsor。由容器自动管理组件之间的依赖关系,但使用框架这不容易控制组件间的依赖关系

Spring.Net（Spring官方站点http://www.springframework.net/）

说明	由java平台上的Spring移植过来，在java平台上有大量拥护者和学习资源，都可以为.net所用。并且现在的spring可以使用注解（java里叫Annotation，类似于类似.net中的Attribute）以减少配置文件的负担。

Unity（CodePlex页面http://www.codeplex.com/unity）

说明	来自微软的Practise & Pattern团队，是Enterprise Library中的一个应用程序块。轻量级，可扩展。

相关资料：http://www.kaiyuan8.org/Article/UyyIMwNiXBYThOIhEvaU.aspx；http://www.codeplex.com/unity

如下就是我们这个demo级的IoC整体设计

IApplicationContext想用户提供使用IoC的接口，它本身继承IContext。

IContext用于存储每个上下文信息和注册的组件。

IRegister（组件注册器）用于向组件注入值，每个注册器中都有一个CurrentContext，当上下文获得注册器时会自动配置此值。同时含有一个IObjectInjector组件用注入。

IResourceManager用于读取配置信息，含有一个IReadAdapter，顾名思义，这是一个适用于各种存储方式的读取适配器接口，比如xml文件，或者是调用远程服务等，不管数据是怎么获得到的，最终对外都提供为XML数据。

配置文件：根节点为Goh（正式的应该加上namespace和xsd文件），每个组件的元素叫Component，Component有name和type属性，还有<Property>子元素用来表示对象中的属性（Property），每个Property元素有name、value、ref三种属性。ref可以用来引用Component。

主要接口定义

public interface IContext     {         object this[string name] { get; set; }         bool QueryExists(string name);         bool RemoveComponent(string name);         Guid ContextId { get; }         IRegister Register{ get; }     } public interface IRegister     {         /// <summary>         /// 将上下文中的名为targetName的对象的property属性设置为property值。默认的反射搜索设置为：BindingFlags.NonPublic | BindingFlags.CreateInstance         /// </summary>         /// <param name="targetName">目标的属性名称</param>         /// <param name="property">注入的属性值</param>         void InjectProperty(string targetName, string propertyName, object property);         void InjectProperty(string targetName, string propertyName, object property, BindingFlags bindingFlags);         IContext CurrentContext { get; set; }     } public interface IConfigureManager     {         IContext GenerateContext();         /// <summary>         /// 自动根据先前配置存储配置IContext对象         /// </summary>         /// <param name="context">GlobalHandler的应用程序上下文</param>         void ConfigContext(IContext context);     } public interface IReadAdapter     {         XElement Config { get; }     }

 

实现代码

public class ConfigureManager : IConfigureManager     {         #region Fields         private IReadAdapter _reader;         #endregion         #region Constructors & Initializer         public ConfigureManager(IReadAdapter reader)         {             _reader = reader;         }         #endregion         #region IConfigureManager 成员         public IContext GenerateContext()         {             return GenerateComponentTable()["applicationContext"] as IContext; ;         }         public void ConfigContext(IContext context)         {             Dictionary<string, object> dict = GenerateComponentTable();             foreach(var key in dict.Keys)             {                 context[key] = dict[key];             }         }         #endregion         #region private Helper Methods         private Dictionary<string, object> GenerateComponentTable()         {             Dictionary<string, object> dict = new Dictionary<string, object>();             XElement config =_reader.Config;             var components = config.Elements("Component");             //先不注入属性而是仅将未初始化的对象存入dict。             foreach(XElement elmt in components)             {                 string name = elmt.Attribute("name").Value;                 string valueType = elmt.Attribute("type").Value;                 Type type = Type.GetType(valueType);                 object realValue = TypeInitializer.Instance.CreateInitObject(type);                 dict.Add(name, realValue);             }             foreach(XElement elmt2 in components)             {                 string curName = elmt2.Attribute("name").Value;                 var properties = elmt2.Elements("Property");                 foreach(XElement prop in properties)                 {                     string propName = prop.Attribute("name").Value;                     XAttribute valueAttr = prop.Attribute("value");                     if(valueAttr != null)                     {                         string propValue = valueAttr.Value;                         ObjectInjector injector = new ObjectInjector();                         Type propType = injector.GetPropertyType(dict[curName], propName);                         object realValue = null;                         if(propType == typeof(int))                         {                             realValue = TypeInitializer.Instance.TransformStringToInteger(propValue);                         }                         else                         {                             realValue = propValue;                         }                         injector.InjectProperty(dict[curName], propName, realValue);                     }                     XAttribute refAttr = prop.Attribute("ref");                     if(refAttr != null)                     {                         object refValue = dict[refAttr.Value];                         ObjectInjector injector = new ObjectInjector();                         injector.InjectProperty(dict[curName], propName, refValue);                     }                 }             }             return dict;         }         #endregion     } public class Context : IContext     {         #region Fields         private Guid _contextId;         private IRegister _register;         private Dictionary<string, object> _componentContainer;         #endregion         #region Constructors & Initializer         public Context()         {             Init();         }         public Context(IRegister register)         {             Init();             InitRegisterProperty(register);         }         private void Init()         {             _contextId = Guid.NewGuid();             _componentContainer = new Dictionary<string, object>();         }         private void InitRegisterProperty(IRegister register)         {             _register = register;             _register.CurrentContext = this;         }         #endregion         #region Properties         public object this[string name]         {             get             {                 if (!_componentContainer.ContainsKey(name))                     throw new ComponentNotFoundException();                 return _componentContainer[name];             }             set             {                 if (_componentContainer.ContainsKey(name))                     throw new ComponentAlreadyExistException();                 _componentContainer.Add(name, value);             }         }         public IRegister Register         {             get             {                 return _register;             }             private set             {                 InitRegisterProperty(value);             }         }         public Guid ContextId         {             get             {                 return _contextId;             }         }         public bool QueryExists(string name)         {             return _componentContainer.ContainsKey(name);         }         public bool RemoveComponent(string name)         {             return _componentContainer.Remove(name);         }         #endregion     } public class DefaultRegister : IRegister     {         #region Fields         IContext _context;         IObjectInjector _objectInjector;         #endregion         #region Constructors & Initializer         public DefaultRegister()         {         }         public DefaultRegister(IObjectInjector objectInjector)         {             _objectInjector = objectInjector;         }         public DefaultRegister(IContext context, IObjectInjector objectInjector)         {             _context = context;             _objectInjector = objectInjector;         }         #endregion         #region IRegister 成员         public IContext CurrentContext         {             get             {                 return _context;             }             set             {                 _context = value;             }         }         public void InjectProperty(string targetName, string propertyName, object property)         {             InjectProperty(targetName, propertyName, property, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);         }         public void InjectProperty(string targetName, string propertyName, object property, BindingFlags bindingFlags)         {             object objTarget = _context[targetName];             _objectInjector.InjectProperty(objTarget, propertyName, property);         }         private IObjectInjector Injector         {             get             {                 return _objectInjector;             }             set             {                 _objectInjector = value;             }         }         #endregion     } public class ObjectInjector : IObjectInjector     {         #region IObjectInjector 成员         public void InjectProperty(object target, string propertyName, object property)         {             InjectProperty(target, propertyName, property, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);         }         public void InjectProperty(object target, string propertyName, object property, BindingFlags bindingFlags)         {             object objTarget = target;             Type type = objTarget.GetType();             PropertyInfo propertyInfo = type.GetProperty(propertyName, bindingFlags);             propertyInfo.SetValue(objTarget, property, null);         }         public Type GetPropertyType(object target, string propertyName)         {             Type type = target.GetType();             PropertyInfo pi = type.GetProperty(propertyName, BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.Instance);             if (pi == null)                 return null;             return pi.PropertyType;         }         #endregion     } public class TypeInitializer     {         #region make it singleton         public static readonly TypeInitializer Instance;         static TypeInitializer()         {             Instance = new TypeInitializer();         }         private TypeInitializer()         {             Init();         }         private void Init()         {             _basicTypes = GetBasicTypes();         }         #endregion         #region Fields         private IList<Type> _basicTypes;         #endregion         public  object CreateInitObject(Type type)         {             if(CheckIsBasicType(type))             {                 return CreateBasicTypeValue(type);             }             else             {                 return Activator.CreateInstance(type);             }         }         public int TransformStringToInteger(string prop)         {             return Int32.Parse(prop);         }         #region private Helper Methods         private IList<Type> GetBasicTypes()         {             IList<Type> types = new List<Type>();             types.Add(typeof(System.Int16));             types.Add(typeof(System.Int32));             types.Add(typeof(System.Int64));             types.Add(typeof(System.String));             //咱不支持数组             return types;         }         private bool CheckIsBasicType(Type type)         {             return _basicTypes.Contains(type);         }         private object CreateBasicTypeValue(Type type)         {             if (type == typeof(System.String))                 return "";             return Activator.CreateInstance(type);         }         #endregion     } public class XmlReadAdapter : IReadAdapter     {         #region Fields         private string _xmlPath;         private XElement _config;         #endregion         #region Constructors & Initializer         public XmlReadAdapter(string xmlPath)         {             _xmlPath = xmlPath;             _config = XDocument.Load(xmlPath).Element("GhRoot");         }         #endregion         #region IReadAdapter 成员         public System.Xml.Linq.XElement Config         {             get             {                 return _config;             }         }         #endregion     }

具体实现代码放到SkyDrive上了，http://qpt2ua.blu.livefilestore.com/y1pJn0xE1aDEE8kAITcT2LgpbjUTX_zjtBTJgyvdHP7Pr1iOV686i8Zu_y-koSE4mZcsrz2YRzx5S-slFOWQPdDloScCFi2MSgw/Demo_IoC.rar?download（不过里面还夹杂了点别的project。。。）

配置文件示例：

Goh.xml

<?xml version="1.0" encoding="utf-8" ?>
<GhRoot>
  <Component name="register" type="GlobalHander.Register.DefaultRegister, GlobalHandler.Context.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
    <Property name="CurrentContext" ref="applicationContext" />
    <Property name="Injector" ref="objectInjector" />
  </Component>

  <Component name="applicationContext" type="GlobalHandler.Context.Context, GlobalHandler.Context.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
    <Property name="Register" ref="register" />
  </Component>

  <Component name="objectInjector" type="GlobalHandler.Register.ObjectInjector, GlobalHandler.Context.Impl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null" />
  </GhRoot>

GohComponent.xml

<?xml version="1.0" encoding="utf-8" ?>
<GhRoot>
  <Component name="entityA" type="TeamTest.Entity, TeamTest, Version=1.0.0.0, Culture=neutral,  PublicKeyToken=null">
    <Property name="a" value="wJiang" />
    <Property name="b" value="124" />
</Component>
  <Component name="entityB" type="TeamTest.Entity, TeamTest, Version=1.0.0.0, Culture=neutral,  PublicKeyToken=null">
    <Property name="a" value="wJiang" />
    <Property name="b" value="124" />
</Component>
  <Component name="entityWrapper" type="TeamTest.Entity2, TeamTest, Version=1.0.0.0, Culture=neutral,  PublicKeyToken=null">
    <Property name="entity" ref="entityA" />
</Component>

  <Component name="entityWrapper2" type="TeamTest.Entity3, TeamTest, Version=1.0.0.0, Culture=neutral,  PublicKeyToken=null">
    <Property name="entity" ref="entityB" />
</Component>

  </GhRoot>