我心中的核心组件（可插拔的AOP）~第十二回 IoC组件Unity

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说在前

Ioc组件有很多，之前也介绍过autofac,castle等，今天再来说一下在微软Nlayer DDD架构里使用的unity组件，今天主要说一下依靠注入，如果希望看拦截的用法，可以阅读这篇文章第十三回 实现AOP的拦截组件Unity.Interception

做在后

unity的用法主要说一下接口注入方法，它包括了程序中注入和配置文件注入，而接口注入还分为普通接口注入和泛型接口注入，下面分别来说一下：

普通接口和类实现代码

　 public interface IUser
{
IQueryable<WebManageUsers> GetEntities();
}
public class UserRepository : BackgroundRepository<WebManageUsers>, IUser
{
public IQueryable<WebManageUsers> GetEntities()
{
return this.GetModel();
}
}

普通接口注入，程序中的注入

using (IUnityContainer container = new UnityContainer())
{
ConfigurationManager.GetSection("unity");
UnityConfigurationSection.CurrentSection.Configure(container);
container.RegisterType<IUser, DataTest.UserRepository>();
var repository = container.Resolve<IUser>();
}

普通接口注入，配置文件中的注入

<unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
<container>
<register  type="EntityTest.IUser,EntityTest" mapTo="DataTest.UserRepository, DataTest" />
</container>
</unity>

using (IUnityContainer container = new UnityContainer())
{
ConfigurationManager.GetSection("unity");
UnityConfigurationSection.CurrentSection.Configure(container);
var repository = container.Resolve<IUser>();
}

普通接口和类实现代码

/// <summary>
/// 基础的数据操作规范
/// </summary>
/// <typeparam name="TEntity"></typeparam>
public interface IRepository<TEntity>
where TEntity : class
{
/// <summary>
/// 添加实体并提交到数据服务器
/// </summary>
/// <param name="item">Item to add to repository</param>
void Insert(TEntity item);

/// <summary>
/// 移除实体并提交到数据服务器
/// 如果表存在约束，需要先删除子表信息
/// </summary>
/// <param name="item">Item to delete</param>
void Delete(TEntity item);

/// <summary>
/// 修改实体并提交到数据服务器
/// </summary>
/// <param name="item"></param>
void Update(TEntity item);

/// <summary>
/// 得到指定的实体集合（延时结果集）
/// Get all elements of type {T} in repository
/// </summary>
/// <returns>List of selected elements</returns>
IQueryable<TEntity> GetModel();

/// <summary>
/// 根据主键得到实体
/// </summary>
/// <param name="id"></param>
/// <returns></returns>
TEntity Find(params object[] id);
}
public class BackgroundRepository<T> : IRepository<T> where T : class
{
#region IRepository<TEntity> 成员

public virtual void Insert(TEntity item)
{
OnBeforeSaved(new SavedEventArgs(item, SaveAction.Insert));
Db.Entry<TEntity>(item);
Db.Set<TEntity>().Add(item);
this.SaveChanges();
OnAfterSaved(new SavedEventArgs(item, SaveAction.Insert));
}

public virtual void Delete(TEntity item)
{
OnBeforeSaved(new SavedEventArgs(item, SaveAction.Delete));
Db.Set<TEntity>().Attach(item);
Db.Set<TEntity>().Remove(item);
this.SaveChanges();
OnAfterSaved(new SavedEventArgs(item, SaveAction.Delete));
}

public virtual void Update(TEntity item)
{
OnBeforeSaved(new SavedEventArgs(item, SaveAction.Update));
Db.Set<TEntity>().Attach(item);
Db.Entry(item).State = EntityState.Modified;
this.SaveChanges();
OnAfterSaved(new SavedEventArgs(item, SaveAction.Update));
}

/// <summary>
/// 子类在实现时，可以重写，加一些状态过滤
/// </summary>
/// <returns></returns>
public virtual IQueryable<TEntity> GetModel()
{
//  return Db.Set<TEntity>().AsNoTracking();//对象无法自动添加到上下文中，因为它是使用 NoTracking 合并选项检索的。请在定义此关系之前，将该实体显式附加到 ObjectContext。
return Db.Set<TEntity>();////ObjectStateManager 中已存在具有同一键的对象。ObjectStateManager 无法跟踪具有相同键的多个对象。
}
/// <summary>
/// 得到原生态结果集
/// </summary>
/// <returns></returns>
public IQueryable<TEntity> GetEntities()
{
return Db.Set<TEntity>();
}
#endregion
　｝

泛型接口注入，程序中的注入

using (IUnityContainer container = new UnityContainer())
{
ConfigurationManager.GetSection("unity");
UnityConfigurationSection.CurrentSection.Configure(container);
container.RegisterType<IRepository<User>, BackgroundRepository<User>>();
var re = container.Resolve<IRepository<User>>();
}

泛型接口注入，配置文件中的注入

<unity xmlns="http://schemas.microsoft.com/practices/2010/unity">
<container>
<register  type="IRepository.Core.IRepository`1,IRepository.Core" mapTo="DataTest.BackgroundRepository`1, DataTest" />
</container>
</unity>

using (IUnityContainer container = new UnityContainer())
{
ConfigurationManager.GetSection("unity");
UnityConfigurationSection.CurrentSection.Configure(container);
var re = container.Resolve<IRepository<User>>();
}

下面我们封装一个服务定位器，让它把Unity容器封装一下，方便以后调用它，下面是ServiceLocator的原代码：

/// <summary>
/// Represents the Service Locator.
/// </summary>
public sealed class ServiceLocator : IServiceProvider
{
#region Private Fields
private readonly IUnityContainer _container;
#endregion

#region Private Static Fields
private static readonly ServiceLocator instance = new ServiceLocator();
#endregion

#region Ctor
/// <summary>
/// Initializes a new instance of ServiceLocator class.
/// </summary>
private ServiceLocator()
{
UnityConfigurationSection section = (UnityConfigurationSection)ConfigurationManager.GetSection("unity");
_container = new UnityContainer();
section.Configure(_container);
}
#endregion

#region Public Static Properties
/// <summary>
/// Gets the singleton instance of the ServiceLocator class.
/// </summary>
public static ServiceLocator Instance
{
get { return instance; }
}
#endregion

#region Private Methods
private IEnumerable<ParameterOverride> GetParameterOverrides(object overridedArguments)
{
List<ParameterOverride> overrides = new List<ParameterOverride>();
Type argumentsType = overridedArguments.GetType();
argumentsType.GetProperties(BindingFlags.Public | BindingFlags.Instance)
.ToList()
.ForEach(property =>
{
var propertyValue = property.GetValue(overridedArguments, null);
var propertyName = property.Name;
overrides.Add(new ParameterOverride(propertyName, propertyValue));
});
return overrides;
}
#endregion

#region Public Methods
/// <summary>
/// Gets the service instance with the given type.
/// </summary>
/// <typeparam name="T">The type of the service.</typeparam>
/// <returns>The service instance.</returns>
public T GetService<T>()
{
return _container.Resolve<T>();
}
/// <summary>
/// Gets the service instance with the given type by using the overrided arguments.
/// </summary>
/// <typeparam name="T">The type of the service.</typeparam>
/// <param name="overridedArguments">The overrided arguments.</param>
/// <returns>The service instance.</returns>
public T GetService<T>(object overridedArguments)
{
var overrides = GetParameterOverrides(overridedArguments);
return _container.Resolve<T>(overrides.ToArray());
}
/// <summary>
/// Gets the service instance with the given type by using the overrided arguments.
/// </summary>
/// <param name="serviceType">The type of the service.</param>
/// <param name="overridedArguments">The overrided arguments.</param>
/// <returns>The service instance.</returns>
public object GetService(Type serviceType, object overridedArguments)
{
var overrides = GetParameterOverrides(overridedArguments);
return _container.Resolve(serviceType, overrides.ToArray());
}
#endregion

#region IServiceProvider Members
/// <summary>
/// Gets the service instance with the given type.
/// </summary>
/// <param name="serviceType">The type of the service.</param>
/// <returns>The service instance.</returns>
public object GetService(Type serviceType)
{
return _container.Resolve(serviceType);
}

#endregion
}

下面再去使用unity时就方便多了，呵呵，看代码：

var model = ServiceLocator.Instance.GetService<IExtensionRepository<WebManageUsers>>().GetModel().ToList();

而使用ServiceLocator还有一个好处，就是不需要使用＂实现的程序集＂，只要把＂实现的程序集＂和它的相关依赖的程序集一起复制到ＷＥＢ项目的ＢＩＮ目录即可，服务定位器会自己去定位的．

好了，讲到这里也就差不多了，需要注意的是，如果你在项目中进行注入时，需要先注入的实现类所在的程序集也引入进来，否则也是不可以resolve出来对象的，而对于业务层（领域）层来说，不需要关心底层

的实现技术，即不需要引用实现类的程序集，而在业务层引用接口程序集即可．

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