摘要：在Castle IOC容器实践之TypedFactory Facility（一）里面大家都已经知道了如何去使用TypedFactory Facility，也已经体会到它的方便之处了，为了更好的使用它，本篇我们对TypedFactory Facility的原理做一些简单的分析。
TypedFactory Facility原理分析
在TypedFactory Facility中，有一个FactoryEntry类，这个类与我们平时项目开发中的实体类有一些类似，它用来记录工厂的相关信息，包括工厂的ID，工厂的接口，创建方法和销毁方法。这个类实现如下：
public class FactoryEntry
{
private String _id;
private Type _factoryInterface;
private String _creationMethod;
private String _destructionMethod;
public FactoryEntry(String id, Type factoryInterface, String creationMethod, String destructionMethod)
{
// 
省略了验证及异常处理
_id = id;
_factoryInterface = factoryInterface;
_creationMethod = creationMethod;
_destructionMethod = destructionMethod;
}
public String Id
{
get { return _id; }
}
public Type FactoryInterface
{
get { return _factoryInterface; }
}
public String CreationMethod
{
get { return _creationMethod; }
}
public String DestructionMethod
{
get { return _destructionMethod; }
}
}
TypedFactoryFacility同样是继承于AbstractFacility，关于Facility的继承关系我在前面的文章中已经说过了。TypedFactory Facility在初始化的时候首先会获取工厂的类型，通过SubSystem来得到：
protected override void Init()
{
Kernel.AddComponent( "typed.fac.interceptor", typeof(FactoryInterceptor) );
ITypeConverter converter = (ITypeConverter)
Kernel.GetSubSystem( SubSystemConstants.ConversionManagerKey );
AddFactories(FacilityConfig, converter);
}
protected virtual void AddFactories(IConfiguration facilityConfig, ITypeConverter converter)
{
if (facilityConfig != null)
{
foreach(IConfiguration config in facilityConfig.Children["factories"].Children)
{
String id = config.Attributes["id"];
String creation = config.Attributes["creation"];
String destruction = config.Attributes["destruction"];
Type factoryType = (Type)
converter.PerformConversion( config.Attributes["interface"], typeof(Type) );
try
{
AddTypedFactoryEntry(
new FactoryEntry(id, factoryType, creation, destruction) );
}
catch(Exception ex)
{
throw new ConfigurationException("Invalid factory entry in configuration", ex);
}
}
}
}
然后再创建一个FactoryEntry实例，记录了工厂的信息，放在了ComponentModel的扩展属性ExtendedProperties中，设置ComponentModel的生命周期为Singleton：
public void AddTypedFactoryEntry( FactoryEntry entry )
{
ComponentModel model =
new ComponentModel(entry.Id, entry.FactoryInterface, typeof(Empty));
model.LifestyleType = LifestyleType.Singleton;
model.ExtendedProperties["typed.fac.entry"] = entry;
model.Interceptors.Add( new InterceptorReference( typeof(FactoryInterceptor) ) );
Kernel.AddCustomComponent( model );
}
在容器中加入一个工厂接口的拦截器FactoryInterceptor，当从容器中获取工厂时，会被拦截器拦截，拦截器的实现如下：
[Transient]
public class FactoryInterceptor : IMethodInterceptor, IOnBehalfAware
{
private FactoryEntry _entry;
private IKernel _kernel;
public FactoryInterceptor(IKernel kernel)
{
_kernel = kernel;
}
public void SetInterceptedComponentModel(ComponentModel target)
{
_entry = (FactoryEntry) target.ExtendedProperties["typed.fac.entry"];
}
public object Intercept(IMethodInvocation invocation, params object[] args)
{
String name = invocation.Method.Name;
if (name.Equals(_entry.CreationMethod))
{
if (args.Length == 0 || args[0] == null)
{
return _kernel[ invocation.Method.ReturnType ];
}
else
{
return _kernel[ (String) args[0] ];
}
}
else if (name.Equals(_entry.DestructionMethod))
{
if (args.Length == 1)
{
_kernel.ReleaseComponent( args[0] );
return null;
}
}
return invocation.Proceed(args);
}
}
还有一点需要我们注意的是在上面实例化ComponentModel的时候用到了一个Empty类，这个类是一个空类，没有任何实现：
在实例化ComponentModel时需要传入的几个参数是：
public ComponentModel(String name, Type service, Type implementation)
{
this.name = name;
this.service = service;
this.implementation = implementation;
this.lifestyleType = LifestyleType.Undefined;
}
即这里用一个空的类型来代替实现了的类型。
本文转自lihuijun51CTO博客，原文链接：http://blog.51cto.com/terrylee/67689 ，如需转载请自行联系原作者