AOP解析——含简单AOP框架实现（包括Proxy模式实现与Attribute实现）实现Castle的AR事务低侵入性
AOP简介：
AOP（Aspect Oriented Programming）“面向切面编程”，其实和OOP（Object Oriented Programming）“面向对象编程”一样是一种编程思路，而且个人以为翻译为“切面导向编程”更为妥当，OOP也应翻译为“对象导向编程”。因为正是有了“切面”和“对象”的想法和概念才产生了“Aspect Oriented Programming”和“Object Oriented Programming”这些编程方法，所以“导向”更为贴近些。
以下想法均为个人揣摩得出，具体官方概念请Google，Bing，Baidu.
AOP，个人以为是一种行为（Behavior）的注入，在不改变原有逻辑（original logic）的基础上，将一些可重用的其他逻辑（other logic）注入到原有逻辑（original logic）中。切面(Aspect)即为其他逻辑（other logic），是一些特殊的业务关注点，包括“事务处理”，“异常捕捉”，“日志记录”，“身份验证”等方面。
这种“切面”逻辑一般贯彻整个解决方案，AOP方式将这种切面提取出来，实现了解耦和代码简洁化。
简单例子：
下面举个简单的例子来说明为什么要使用AOP：
1）没有使用AOP的Castle ActiveRecord“事务处理”
代码
{
// ......
/// <summary>
/// Save the retire user info.
/// </summary>
/// <param name="site"> The user will be retire user. </param>
public void SaveRetireUserInfo(User user)
{
using (TransactionScope transaction = new TransactionScope())
{
try
{
RetireUser retireUser = new RetireUser();
retireUser.Name = user.Name;
retireUser.Department = user.Department;
// ...
user.Delete();
retireUser.Save();
transaction.VoteCommit(); // 完成事务
}
catch (Exception ex)
{
Log.Write(ex.Message);
transaction.VoteRollBack(); // 事务回滚
}
}
}
// ......
}
2）使用AOP的Castle ActiveRecord“事务处理”, 里边使用了我自己写的精简AOP框架，与原来的文章一样，看不懂没关系，这里只是个宏观的概念。重点在demo分析。
代码
/// The test class for AOP use attribute for transaction.
/// </summary>
[AOPProxy(Interception = typeof (TransactionInterception))]
class AOPTest : ContextBoundObject
{
// ......
/// <summary>
/// Save the retire user info.
/// </summary>
/// <param name="site"> The user will be retire user. </param>
public void SaveRetireUserInfo(User user)
{
RetireUser retireUser = new RetireUser();
retireUser.Name = user.Name;
retireUser.Department = user.Department;
// ...
user.Delete();
retireUser.Save();
}
// ......
}
/// <summary>
/// The interception of the AOP for trasaction.
/// </summary>
class TransactionInterception : IInterception
{
private TransactionScope transaction = null ;
#region IInterception Members
public void ExceptionHandle()
{
transaction.VoteRollBack(); // 事务回滚
}
public void PostInvoke()
{
transaction.VoteCommit(); // 完成事务
}
public void PreInvoke()
{
transaction = new TransactionScope(); // 初始化事务
}
#endregion
}
由以上可见，加入AOP后（AOPProxy Attribute实现），“其他逻辑”注入“原始逻辑”使得代码更加简洁，同时也将“切面”的逻辑和“业务”的逻辑分离开来，实现了解耦。TransactionInterception是拦截器，实现了“其他逻辑”，由AOPProxy Attribute通过type将其注入。在处理“原始逻辑”的时候会同时处理注入的“其他逻辑”。ExceptionHandle方法实现出现Exception时的“其他逻辑”注入；PreInvoke方法实现在调用“主题”方法前的“其他逻辑”注入；PostInvoke方法实现在调用“主题”方法后的“其他逻辑”注入。
简单来说执行流程如下：
1. PreInvoke();
2. 主题Method();
3.
if(调用"主题Method()"时出现Exception)
{
ExceptionHandle();
}
else
{
PostInvoke();
}
有下面的SaveRetireUserInfo方法可以看到“业务逻辑”变得简洁，在“业务逻辑”已经见不到扰乱代码可读性的“事务代码”和“try...catch...”语句块了，只需要给该类加上“AOPProxy”特性注入相应的“拦截器”并继承ContextBoundObject即可。
public void SaveRetireUserInfo(User user)
{
RetireUser retireUser = new RetireUser();
retireUser.Name = user.Name;
retireUser.Department = user.Department;
// ...
user.Delete();
retireUser.Save();
}
Proxy基础:
代理模式，说白了就是设置一个“中间层”（proxy），把对实际要操作的“主题”保护在里边，并且在操作时进行额外的操作，实现注入。对“主题”的操作均需要通过proxy来完成，就如同经济人。
比如：你是著名歌星SexyBaby，你有一个经纪人叫Underdog，你只负责唱歌，各种演唱会的举办和电视台对你邀请一律由Underdog负责，你SexyBaby就是“主题”而你的经纪人Underdog就是proxy。
具体的代理模式可以看我以前写的关于Dota的设计模式随笔和各种设计模式书籍。
下面介绍个简单的例子来了解下代理模式。
假设一个场景：IT界优秀人士均喜欢看AV，而由于为了保护我们国家未成年人幼小的心灵不受到不良网站侵害，国家屏蔽了AV站点，那我们这些IT界寂寞哥又有这样的需求，那该怎么办那？我们需要通过Online Web Proxy来解决这个问题，我们通过这样的“在线代理网站”（“在线代理网站”服务器放在不屏蔽AV站点的国家，由“在线代理网站”服务器间接访问AV站点。因为在线代理网站不直接提供AV信息，所以我们是可以访问的）来访问AV站点就可以了。这时我们是通过Proxy（“在线代理网站”）访问到“主题”（AV站点），对Proxy（“在线代理网站”）的操作和直接操作“主题”（AV站点）没有什么区别。
下面就开始我们的AV之旅吧，由于上次有同学说我代码里用中文，怪怪的，这次都用英文，顺便让大家复习下英文了:
1) 首先我们必须有一台链接到Internet的电脑“MyComputer”。
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// My PC.
/// </summary>
public class MyComputer
{
/// <summary>
/// Visit the site.
/// </summary>
/// <param name="site"> The site. </param>
public void Visit(ISite site)
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine( " Site Url:{0} " , site.Url);
Console.ForegroundColor = ConsoleColor.White;
IFilter filter = new ChinaDNSFilter(); // Server in China, comply with the rule of China.
site = filter.Parse(site); // Parse the site.
Console.ForegroundColor = ConsoleColor.Gray;
site.ShowInformation(); // Show the information of the site.
Console.ForegroundColor = ConsoleColor.White;
}
}
}
“MyComputer”有一个Visit方法，可以访问到传入的ISite（抽象出的站点接口），Visit方法流程如下：
1） 输出当前站点ISite的Url。下面的Code是ISite的定义。
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// The interface of site.
/// </summary>
public interface ISite
{
/// <summary>
/// The url of site.
/// </summary>
string Url
{
get ;
}
/// <summary>
/// Show the information about this site.
/// </summary>
void ShowInformation();
}
}
另外我们设计了几个站点以供访问，代码如下：
首先是传说中的AVSite（http://www.avsite.com/），看看介绍多么吸引人“The site is so hot, all AV stars.”。
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// The site contains AV information.
/// </summary>
public class AVSite : ISite
{
#region ISite Members
/// <summary>
/// The url of site.
/// </summary>
public string Url
{
get { return " http://www.AVSite.com " ; }
}
/// <summary>
/// Show the information about this site.
/// </summary>
public void ShowInformation()
{
Console.WriteLine( " The site is so hot, all AV stars. " );
}
#endregion
}
}
然后是我们经常上的博客园“http://www.cnblogs.com”，介绍“The technology site, the home of coders.”。
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// The site of cnblogs.
/// </summary>
public class CnblogsSite : ISite
{
#region ISite Members
/// <summary>
/// The url of site.
/// </summary>
public string Url
{
get { return " http://www.cnblogs.com " ; }
}
/// <summary>
/// Show the information about this site.
/// </summary>
public void ShowInformation()
{
Console.WriteLine( " The technology site, the home of coders. " );
}
#endregion
}
}
下面该我们的主角出场了，“在线代理网站”“http://www.myproxy.com”。我们可以通过构造函数传入想要代理访问的站点地址，传入站点地址后会通过DNS解析访问到相应的网站。“在线代理网站”和“DNS（Domain Name Resolution）”的实现（执行“在线代理网站”的ShowInformation方法时实际是通过代理显示要代理网站（AV站点）的信息）。
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// The online web proxy site.
/// </summary>
public class MyProxySite : ISite
{
private ISite _site = null ;
public MyProxySite( string url)
{
_site = DNS.GetSite(url);
}
#region ISite Members
/// <summary>
/// The url of site.
/// </summary>
public string Url
{
get { return " http://www.myproxy.com " ; }
}
/// <summary>
/// Show the information about this site.
/// </summary>
public void ShowInformation()
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine( " Proxy start! " );
Console.WriteLine( " Real url:{0} " , _site.Url);
Console.ForegroundColor = ConsoleColor.Gray;
IFilter filter = new USADNSFilter(); // Server in USA, comply with the rule of USA.
_site = filter.Parse(_site);
_site.ShowInformation();
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine( " Proxy end! " );
Console.ForegroundColor = ConsoleColor.Gray;
}
#endregion
}
}
DNS
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// Domain name resolution.
/// </summary>
class DNS
{
/// <summary>
/// Get the site instance by the url.
/// </summary>
/// <param name="url"> The visited url. </param>
/// <returns> The site instance. </returns>
public static ISite GetSite( string url)
{
ISite site = null ;
if (url == " http://www.AVSite.com " )
{
site = new AVSite();
}
else if (url == " http://www.cnblogs.com " )
{
site = new CnblogsSite();
}
else
{
site = new NullSite();
}
return site;
}
}
}
另外当DNS中不包含传入的网址时要返回“NullSite”，用“MyComputer”直接访问“AVSite”时，会被“ChinaFilter”过滤，返回“WarnningSite”提醒访问者触犯法律。“NullSite”和“WarnningSite”实现如下。
NullSite：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// The site with nothing.
/// </summary>
public class NullSite : ISite
{
#region ISite Members
/// <summary>
/// The url of site.
/// </summary>
public string Url
{
get { return String.Empty; }
}
/// <summary>
/// Show the information about this site.
/// </summary>
public void ShowInformation()
{
Console.WriteLine( " No site, please check the url. " );
}
#endregion
}
}
WarnningSite：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// The site for the warnning of gov.
/// </summary>
public class WarnningSite : ISite
{
#region ISite Members
/// <summary>
/// The url of site.
/// </summary>
public string Url
{
get { return String.Empty; }
}
/// <summary>
/// Show the information about this site.
/// </summary>
public void ShowInformation()
{
Console.WriteLine( " For the gov rule, this site can't be visited. " );
}
#endregion
}
}
2） 根据中国法律由ISP（Internat Service Provider）服务器过滤网站，返回相应的站点对象。
过滤接口实现如下：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// The interface of the site visiting filter.
/// </summary>
public interface IFilter
{
/// <summary>
/// Parse the site.
/// </summary>
/// <param name="site"> The site. </param>
/// <returns> The new site. </returns>
ISite Parse(ISite site);
}
}
中国过滤器，过滤掉AVSite，过滤后返回WarnningSite，实现如下：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// ISP(Internet Service Provider),filter the visited site information for comply the rule of China.
/// </summary>
public class ChinaDNSFilter : IFilter
{
#region IFilter Members
/// <summary>
/// Parse the site.
/// </summary>
/// <param name="site"> The site. </param>
/// <returns> The new site. </returns>
public ISite Parse(ISite site)
{
// For the children, no AV information.
ISite returnSite = site;
if (site is AVSite)
{
returnSite = new WarnningSite();
}
return returnSite;
}
#endregion
}
}
美国过滤器，不过滤AVSite，直接返回AVSite，实现如下：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.ProxyPattern
{
/// <summary>
/// ISP(Internet Service Provider),filter the visited site information for comply the rule of USA.
/// </summary>
class USADNSFilter : IFilter
{
#region IFilter Members
/// <summary>
/// Parse the site.
/// </summary>
/// <param name="site"> The site. </param>
/// <returns> The new site. </returns>
public ISite Parse(ISite site)
{
// Freedom, no filter.
return site;
}
#endregion
}
}
3） 通过_site.ShowInformation显示站点信息。
虚拟Internat已经搭建起来，可以进行测试啦。
首先用“MyComputer”直接访问AVSite，返回WarnningSite:
MyComputer myComputer = new MyComputer();
ISite site = new AVSite();
myComputer.Visit(site); // Visit AV site will be return warning.
结果：
然后用“MyComputer”通过“MyProxySite”在线代理网站，代理访问AVSite，返回AVSite站点信息，偶也～～～～
site = new MyProxySite("http://www.avsite.com/"); // Use online web proxy.
myComputer.Visit(site);
结果：
最后看完AV，我们再会博客园逛一逛
site = new CnblogsSite();
myComputer.Visit(site);
结果：
花了很大的功夫说代理，现在该切入正题了，我们的AOP，分为代理模式实现和Attribute实现。
AOP框架实现
首先AOP实现了逻辑注入，即在调用方法之前进行了逻辑注入。我们使用System.Runtime.Remoting中呃Message机制来实现Message的截获和注入，有点像MFC框架中的钩子函数。
首先，为了实现逻辑注入，我们先要设计出逻辑注入的接口（IInterception）。为了简单起见逻辑注入我们只设计了3个Method，包括PreInvoke，PostInvoke和ExceptionHandle，分别用来注入“调用主题Method前的逻辑”，“调用主题Method后的逻辑”和“调用主题Method时发生Exception的逻辑”。具体实现如下：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
namespace Landpy.AOP
{
/// <summary>
/// Description of IInterception.
/// </summary>
public interface IInterception
{
/// <summary>
/// Pre the method invoke.
/// </summary>
void PreInvoke();
/// <summary>
/// Post the method invoke.
/// </summary>
void PostInvoke();
/// <summary>
/// Handling the exception which occurs when the method is invoked.
/// </summary>
void ExceptionHandle();
}
}
逻辑注入的接口（IInterception）永远不为null，根据Null Object模式设计了NullInterception（关于Null Object模式及其意义可以看我原来的文章），实现如下：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.AOP
{
/// <summary>
/// Null Object pattern for interception.
/// </summary>
public class NullInterception : IInterception
{
#region IInterception Members
/// <summary>
/// Before invoke the real instance to do something.
/// </summary>
public virtual void PreInvoke()
{
// Do nothing.
}
/// <summary>
/// End invoke the real instance to do something.
/// </summary>
public virtual void PostInvoke()
{
// Do nothing.
}
/// <summary>
/// Handling the exception which occurs when the method is invoked.
/// </summary>
public void ExceptionHandle()
{
// Do nothing.
}
#endregion
}
}
为了实现Message拦截，我们必须实现一个继承了“RealProxy”的类“AOPRealProxy”，这样我们就可以重写System.Runtime.Remoting.Messaging.IMessage Invoke(System.Runtime.Remoting.Messaging.IMessage msg)方法来注入自己的逻辑。
有的时候代码能更清楚的表达，所以先将AOPRealProxy的实现附上：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.Remoting;
using System.Runtime.Remoting.Proxies;
using System.Runtime.Remoting.Messaging;
using System.Runtime.Remoting.Services;
using System.Runtime.Remoting.Activation;
namespace Landpy.AOP
{
/// <summary>
/// RealProxy is a abstract class, which is a class in Framework to provide the function about base proxy.
/// The Invoke method like the hook of MFC, it intercept the message, inject the custom logic and generate a new message
/// for system to performance.
/// </summary>
class AOPRealProxy : RealProxy, IProxyDI
{
private MarshalByRefObject _target = null ;
private IInterception _interception = null ;
public AOPRealProxy(Type targetType, MarshalByRefObject target)
: base (targetType)
{
_target = target;
_interception = new NullInterception();
}
/// <summary>
/// Overridden the method "Invoke" of the base class, invokes the method that is specified
// in the provided System.Runtime.Remoting.Messaging.IMessage on the remote
// object that is represented by the current instance.
/// </summary>
/// <param name="msg"> A System.Runtime.Remoting.Messaging.IMessage that contains a System.Collections.IDictionary
// of information about the method call.
// </param>
/// <returns> The message returned by the invoked method, containing the return value and
// any out or ref parameters.
// </returns>
public override System.Runtime.Remoting.Messaging.IMessage Invoke(System.Runtime.Remoting.Messaging.IMessage msg)
{
IMethodReturnMessage methodReturnMessage = null ;
IMethodCallMessage methodCallMessage = msg as IMethodCallMessage; // Check whether the message is method call message.
if (methodCallMessage != null )
{
IConstructionCallMessage constructionCallMessage = methodCallMessage as IConstructionCallMessage;
if (constructionCallMessage != null ) //Constructor Method.
{
RealProxy defaultProxy = RemotingServices.GetRealProxy(_target);
defaultProxy.InitializeServerObject(constructionCallMessage);
methodReturnMessage = EnterpriseServicesHelper.CreateConstructionReturnMessage(constructionCallMessage, (MarshalByRefObject)GetTransparentProxy()); //Create the message about constructor.
}
else //Other method except constructor method.
{
_interception.PreInvoke(); //Inject PreInvoke method.
try
{
methodReturnMessage = RemotingServices.ExecuteMessage(_target, methodCallMessage); //Invoke subject method.
}
catch
{
}
if (methodReturnMessage.Exception != null )
{
_interception.ExceptionHandle(); //Occur exception and then inject ExceptionHandle method.
}
else
{
_interception.PostInvoke(); //Inject PostInvoke method.
}
}
}
return methodReturnMessage;
}
#region IProxyDI Members
/// <summary>
/// Dependency injection the interception into proxy class.
/// </summary>
/// <param name="interception"> The interception. </param>
public void InterceptionDI(IInterception interception)
{
_interception = interception; //The pattern of interface inject, inject the interception.
}
#endregion
}
}
使用接口注入方式，将Interception“拦截器”注入到“AOPRealProxy”类。
注入接口“IProxyDI”设计如下:
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.AOP
{
interface IProxyDI
{
void InterceptionDI(IInterception interception);
}
}
1) 实现Proxy模式AOP：
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Collections.Generic;
using System.Text;
namespace Landpy.AOP
{
public class ProxyFactory
{
public static T CreateProxyInstance < T > (IInterception interception) where T : new ()
{
Type serverType = typeof (T);
MarshalByRefObject target = Activator.CreateInstance(serverType) as MarshalByRefObject;
AOPRealProxy aopRealProxy = new AOPRealProxy(serverType, target);
aopRealProxy.InterceptionDI(interception);
return (T)aopRealProxy.GetTransparentProxy();
}
}
}
实现了interception参数注入AOPRealProxy，将包装完成的传输代理类返回。此时返回的代理类对象操作起来如同直接操作“主题”。
2）实现Attribute模式AOP
代码
// Authors:
// Xiaoliang Pang (mailto:[email protected])
//
// Copyright (c) 2010 Landpy Software
//
// http://www.cnblogs.com/pangxiaoliang
//
using System;
using System.Runtime.Remoting.Proxies;
namespace Landpy.AOP
{
/// <summary>
/// Description of AOPProxyAttribute.
/// </summary>
[AttributeUsage(AttributeTargets.Class)]
public class AOPProxyAttribute : ProxyAttribute
{
private IInterception _interception;
public Type Interception
{
get
{
return _interception.GetType();
}
set
{
IInterception interception = Activator.CreateInstance(value) as IInterception;
_interception = interception;
}
}
public AOPProxyAttribute()
{
_interception = new NullInterception();
}
public override MarshalByRefObject CreateInstance(Type serverType)
{
MarshalByRefObject target = base .CreateInstance(serverType);
AOPRealProxy aopRealProxy = new AOPRealProxy(serverType, target);
aopRealProxy.InterceptionDI(_interception);
return aopRealProxy.GetTransparentProxy() as MarshalByRefObject;
}
}
}
实现了interception的Attribute用type注入AOPRealProxy，将包装完成的传输代理类返回。此时返回的代理类对象操作起来如同直接操作“主题”。
测试AOP框架
（一）测试代理模式AOP。
// Proxy class to implement the AOP.
IInterception interception = new MyInterception();
AOPTestWithProxyClass aopTestTwo = ProxyFactory.CreateProxyInstance<AOPTestWithProxyClass>(interception) as AOPTestWithProxyClass;
aopTestTwo.Show();
首先实例化了一个MyInterception的拦截器，然后用ProxyFactory将Interception作为传入注入“主题”。
MyInterception实现如下：
代码
/// The interception of the AOP.
/// </summary>
class MyInterception : IInterception
{
#region IInterception Members
/// <summary>
/// Before invoke the real instance to do something.
/// </summary>
public void PreInvoke()
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine( " ===Pre MyInterception.=== " );
Console.ForegroundColor = ConsoleColor.Gray;
}
/// <summary>
/// End invoke the real instance to do something.
/// </summary>
public void PostInvoke()
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine( " ===Post MyInterception.=== " );
Console.ForegroundColor = ConsoleColor.Gray;
}
/// <summary>
/// Handling the exception which occurs when the method is invoked.
/// </summary>
public void ExceptionHandle()
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine( " There is a exception! " );
Console.ForegroundColor = ConsoleColor.Gray;
}
#endregion
}
AOPTestWithProxyClass实现如下：
代码
/// The test class for AOP use proxy class.
/// </summary>
class AOPTestWithProxyClass : ContextBoundObject
{
public void Show()
{
Console.ForegroundColor = ConsoleColor.Gray;
Console.WriteLine( " Hello, I am AOPTestTwo. " );
Console.ForegroundColor = ConsoleColor.Gray;
}
}
结果：
可见"===Pre MyInterception.==="和"===Post MyInterception.==="已经成功实现AOP注入。
（二）测试Attribute实现AOP。
// Attribute to implement the AOP.
AOPTestWithAttribute aopTest = new AOPTestWithAttribute();
aopTest.Show();
此时的代码要比Proxy实现更为简单，直接用类的构造函数实现类的实例化，不用ProxyFactory生成实例，Interception同样还是使用了MyInterception。
AOPTestWithAttribute类的实现如下：
代码
/// The test class for AOP use attribute..
/// </summary>
[AOPProxy(Interception = typeof (MyInterception))]
class AOPTestWithAttribute : ContextBoundObject
{
public void Show()
{
Console.ForegroundColor = ConsoleColor.Gray;
Console.WriteLine( " Hello, I am AOPTest. " );
Console.ForegroundColor = ConsoleColor.Gray;
}
}
结果：
（三）测试Attribute实现AOP[事务的提交和回滚]。
AOPTestWithAttributForTrasaction aopTestWithAttributForTrasaction = new AOPTestWithAttributForTrasaction();
// Execute the transaction successfully.
aopTestWithAttributForTrasaction.ExecuteTransactionSuccessfully();
WriteSplitLine();
// Execute the transaction unsuccessfully.
try
{
aopTestWithAttributForTrasaction.ExecuteTransactionUnsuccessfully();
}
catch (Exception ex)
{
Console.ForegroundColor = ConsoleColor.Blue;
Console.WriteLine(ex.Message);
Console.ForegroundColor = ConsoleColor.Gray;
}
在ExecuteTransactionUnsuccessfully方法中加入throw Excetpion代码，实现执行不成功的情况。当执行ExecuteTransactionSuccessfully方法时实现事务的提交，当执行ExecuteTransactionUnsuccessfully实现事务的回滚，此时的例子可以对照前面所将的Castle ActiveRecord的事务实现AOP的例子。
AOPTestWithAttributForTrasaction实现如下：
代码
class AOPTestWithAttributForTrasaction : ContextBoundObject
{
public void ExecuteTransactionSuccessfully()
{
Console.WriteLine( " Execute the transaction successfully:) " );
}
public void ExecuteTransactionUnsuccessfully()
{
Console.WriteLine( " Execute the transaction unsuccessfully:( " );
throw new AOPNullException();
}
}
Interception使用了新的TransactionInterception，TransactionInterception的实现如下：
代码
/// The interception of the AOP for trasaction.
/// </summary>
class TransactionInterception : IInterception
{
#region IInterception Members
public void ExceptionHandle()
{
Console.ForegroundColor = ConsoleColor.Red;
Console.WriteLine( " ☆☆☆Rollback transaction☆☆☆ " );
Console.ForegroundColor = ConsoleColor.Gray;
}
public void PostInvoke()
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine( " ☆☆☆Commit transaction☆☆☆ " );
Console.ForegroundColor = ConsoleColor.Gray;
}
public void PreInvoke()
{
Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine( " ☆☆☆Begin transaction☆☆☆ " );
Console.ForegroundColor = ConsoleColor.Gray;
}
#endregion
}
结果：
注意：在Debug下执行到“throw new AOPNullException();”时会停止，继续F5即可执行，如果非Debug状态（如直接双击exe执行），则可以执行到结束。
这是由Debug机制造成的，不必在意。
本人实现的AOP框架是基于ContextBoundObject，MarshalByRefObject的，在效率上会差一些，当然我们可以用反射的高级内容Emit直接生成IL注入原始程序逻辑来实现AOP，有空写篇文章介绍下:)