接触AOP也有些日子，今天事情不多做了个用Proxy模式对AOP的简单实现，贴上来供大家指点一二

AOP(面向方面)设计概念流行已经不少日子了，一直以来对这方面进行了不少了解，今天终于有幸可以小试一下，下面把具体实现过程供大家参考

1、定义代理类，代理类从RealProxy继承实现，关键的方法是Invoke，对对象的请求的附加功能都在这个方法里实现代码如下：

using System;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Proxies;
using System.Runtime.Remoting.Activation;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Services;
using System.Security.Permissions;

namespace ProxyTest
{
 /// <summary>
 /// AOP代理类
 /// </summary>
 public class AspectProxy : RealProxy
 {
  private MarshalByRefObject _Target = null;

  public AspectProxy() : base()
  {
  }

  public AspectProxy(Type serverType) : base(serverType)
  {
  }

  public AspectProxy(Type serverType,MarshalByRefObject target) : base(serverType)
  {
   this._Target = target;
  }

  public override System.Runtime.Remoting.Messaging.IMessage Invoke(System.Runtime.Remoting.Messaging.IMessage msg)
  {
   IMessage retMsg = null;;

   if(msg is IConstructionCallMessage)
   {
    IConstructionCallMessage ccm = (IConstructionCallMessage)msg;

    //用结构调用请求， 初始化当前代理的真实代理所表示的远程对象的对象类型的实例
    RemotingServices.GetRealProxy(this._Target).InitializeServerObject(ccm);

    //将远程对象转换为本地带URL和Type的ObjRef对象
    ObjRef oRef = RemotingServices.Marshal(this._Target);

    //从oRef创建一个代理对象
    RemotingServices.Unmarshal(oRef);

    retMsg = EnterpriseServicesHelper.CreateConstructionReturnMessage(ccm,
     (MarshalByRefObject)this.GetTransparentProxy());
   }
   else
   {
    IMethodCallMessage mcm = (IMethodCallMessage)msg;
    retMsg = RemotingServices.ExecuteMessage(this._Target,mcm);

    //对方法调用记录日志，在这里加入其他处理
    MethodCallLog.AddLog(mcm.MethodBase.ReflectedType.ToString() + "."
     + mcm.MethodName + "/t" + DateTime.Now.ToString());
   }

   return retMsg;
  }

 }
}

下面是日志的实现类，比较简单:

using System;
using System.IO;

namespace ProxyTest
{
 /// <summary>
 /// MethodCallLog 的摘要说明。
 /// </summary>
 public class MethodCallLog
 {
  public static void AddLog(string message)
  {
   StreamWriter w =
    new StreamWriter(System.AppDomain.CurrentDomain.BaseDirectory + "MethodCall.log",true);

   w.WriteLine(message);

   w.Close();
  }
 }
}

2、定义一个AOP对象处理特性，AspectAttribute从ProxyAtrribute继承实现，用来标识对象类型需要自定义代理实现,代码发下： 

using System;
using System.Security.Permissions;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Proxies;

namespace ProxyTest
{
 /// <summary>
 /// 标识类需要进行AOP处理
 /// </summary>
 [AttributeUsage(AttributeTargets.Class)]
 [SecurityPermission(SecurityAction.Demand,Flags=SecurityPermissionFlag.Infrastructure)]
 public class AspectAttribute : ProxyAttribute
 {
  public override MarshalByRefObject CreateInstance(Type serverType)
  {
   MarshalByRefObject mobj = base.CreateInstance (serverType);

   RealProxy proxy = new AspectProxy(serverType,mobj);

   return proxy.GetTransparentProxy() as MarshalByRefObject;
  }

 }
}

 3、紧接着，定义了一个类，标识为需要做AOP处理

using System;

namespace ProxyTest
{
 /// <summary>
 /// AOP处理对象
 /// </summary>
 [Aspect()]
 public class AspectObject : ContextBoundObject
 {
  private int _value;

  public AspectObject()
  {
   //
   // TODO: 在此处添加构造函数逻辑
   //
  }

  public AspectObject(int value)
  {
   this._value = value;
  }

  public void Add(int value)
  {
   this._value += value;
  }
 }
}

编译运行，可以在Bin/Debug下看到 MethodCall.log内容如下：

ProxyTest.AspectObject.Add 2006-3-10 15:31:48 ProxyTest.AspectObject.Add 2006-3-10 15:31:53 ProxyTest.AspectObject.Add 2006-3-10 15:31:54 ProxyTest.AspectObject.Add 2006-3-10 15:31:54 ProxyTest.AspectObject.Add 2006-3-10 15:31:54 ProxyTest.AspectObject.Add 2006-3-10 15:31:55 ProxyTest.AspectObject.Add 2006-3-10 15:31:55 ProxyTest.AspectObject.Add 2006-3-10 15:31:55 ProxyTest.AspectObject.Add 2006-3-10 15:31:55 ProxyTest.AspectObject.Add 2006-3-10 15:31:56 ProxyTest.AspectObject.Add 2006-3-10 15:31:56

到此一个简单的AOP实现已经做完，当然实际应用比这要复杂得多，不过基本过程一样，有不对或者不合理的地方，大家多多指点