使用PostSharp进行AOP框架设计：一个简单的原型

AOP已经不是一个什么新名词了，在博客园使用关键字搜索可以查出n多条关于AOP的介绍，这里就不再赘述了。

在Bruce Zhang's Blog里面有很多关于AOP介绍及其在.net下实现研究，总觉得如果什么都从头来写难免有自造轮子的嫌疑，但是目前也没有很成熟的AOP框架让我们能轻松完成基于AOP架构，不过一直以来都在关注的PostSharp开源项目日趋成熟，目前已发布了PostSharp 1.0 (Beta release 3)。即使如此，也还没能到应用到产品上的时候。

前段时间一直在封装一个权限系统，时常为如何给调用方提供一个良好的编程接口烦恼，加之前前段时间考虑的日志、异常接管、事务、缓存等等一些横向组件的架构分析，自然就想用AOP技术实现，但是由于实现难度实在不小作罢；这两天又重新学习研究了PostSharp的架构与实现思想，觉得还是尝试一下，将其融入现有框架；

早在年初就有不少前辈大师就如何使用这个东西撰写过文章，如Q.yuhen的PostSharp - Lightweight Aspect-Oriented System该仁兄下面见解很到位：



另外有一老外的Using AOP and PostSharp to Enhance Your CodeAB两部分，相当精彩，本文就是在参考这两篇好文的基础上做的。

我们假设有这么个场景，其实这也是实际业务中很常见的处理方式：有一定单管理模块，具备新增、删除两功能，我们在新增删除的时候必须校验权限，在删除的时候还必须记录日志，出现异常了还必须捕捉并记录异常；

按以前的写法我们可能很麻烦,我们要如此这般的写：

public class Orders

{

public bool Add(string id, string orderName)

{

try

{

if (User.AddEnable)

{

//TODO：新增订单的实现

Console.WriteLine("正在执行新增订单方法的操作，回车继续……");

Console.ReadLine();

Console.WriteLine("您添加订单成功：编号：{0}，名称：{1}", id, orderName);

return true;

}

else

{

//

}

}

catch (Exception)

{

//TODO:记录异常的实现

throw;

}

return true;

}

public bool Delete(string id)

{

try

{

if (User.DeleteEnable)

{

//TODO：删除订单的实现

Console.WriteLine("您删除订单成功：编号：{0}", id);

}

else

{

//

}

}

catch (Exception)

{

//TODO:记录异常的实现

throw;

}

return true;

}

这种写的弊端我就不多说了，有很多先驱都阐述过……


我要演示的是采用AOP技术的框架原型实现：

首先我们应该安装PostSharp（一定要安装要不能没办法注入处理代码）

然后我们实现Orders对象

using System;

namespace PostSharp.Demo

{

public class Orders

{

[Permission]

[Exception]

public bool Add(string id, string orderName)

{

Console.WriteLine("正在执行新增订单方法的操作，回车继续……");

Console.ReadLine();

Console.WriteLine("您添加订单成功：编号：{0}，名称：{1}", id, orderName);

return true;

}

[Logger]

[Permission]

[Exception]

public bool Delete(string id)

{

Console.WriteLine("您删除订单成功：编号：{0}", id);

return true;

}

}

}

当然还要模拟一个用户资格认证

namespace PostSharp.Demo

{

/// <summary>

/// 静态的用户对象，用于存放当前登录用户，成员资格

/// </summary>

public static class User

{

private static string _userId;

public static string UserId

{

get { return _userId; }

set { _userId = value; }

}

public static bool AddEnable

{

get

{

return (_userId.ToLower() == "admin");

}

}

public static bool DeleteEnable

{

get

{

return (_userId.ToLower() == "admin");

}

}

}

}

再然后我们实现权限控制方面PermissionAttribute，日志方面LoggerAttribute，异常处理方面ExceptionAttribute……


PermissionAttribute

using System;

using PostSharp.Laos;

namespace PostSharp.Demo

{

[Serializable]

[global::System.AttributeUsage(AttributeTargets.All, Inherited = true, AllowMultiple = false)]

public class PermissionAttribute : OnMethodBoundaryAspect

{

public override void OnEntry(MethodExecutionEventArgs eventArgs)

{

if (!User.AddEnable)

{

Console.WriteLine("用户：【{0}】没有权限：【{1}】", User.UserId, eventArgs.Method);

eventArgs.FlowBehavior = FlowBehavior.Return;

}

}

}

}

LoggerAttribute

using System;

using PostSharp.Laos;

namespace PostSharp.Demo

{

[Serializable]

[global::System.AttributeUsage(AttributeTargets.All, Inherited = true, AllowMultiple = false)]

public sealed class LoggerAttribute : OnMethodInvocationAspect

{

public override void OnInvocation(MethodInvocationEventArgs eventArgs)

{

DateTime time = DateTime.Now;

string log = "时间:{0},操作人员:{1},操作:{2}!";

object[] arg = eventArgs.GetArguments();

log = String.Format(log, time, User.UserId, "删除Id为" + arg[0].ToString() + "的订单！");

System.IO.File.WriteAllText("C:\\Log.Txt", log);

}

}

}

ExceptionAttribute

using System;

using PostSharp.Laos;

namespace PostSharp.Demo

{

[Serializable]

[global::System.AttributeUsage(AttributeTargets.All, Inherited = true, AllowMultiple = false)]

public class ExceptionAttribute : OnExceptionAspect

{

public override void OnException(MethodExecutionEventArgs eventArgs)

{

Console.WriteLine("程序出现异常：{0}", eventArgs.Exception.Message);

eventArgs.FlowBehavior = FlowBehavior.Return;

}

}

}

然后再用控制台程序测试下能不能成功

Orders order = new Orders();

Console.WriteLine("请输入用户名：");

User.UserId = Console.ReadLine();

Console.WriteLine("请输入密码：");

Console.ReadLine();

string id;

LRedo:

Console.WriteLine("请输入您要执行的操作：新增（A），删除（D），退出（X）");

string opt = Console.ReadLine();

if (opt.ToLower() == "a")

{

Console.WriteLine("请输入订单编号：");

id = Console.ReadLine();

Console.WriteLine("请输入订单名称：");

string name = Console.ReadLine();

order.Add(id, name);

}

else if (opt.ToLower() == "d")

{

Console.WriteLine("请输入订单编号：");

id = Console.ReadLine();

order.Delete(id);

}

else if (opt.ToLower() == "x")

{

}

else

{

Console.WriteLine("您的输入不正确，请重新输入！");

goto LRedo;

}

Console.WriteLine("按任意键退出……");

Console.ReadLine();

写完这些我们再反编译一下生成的exe文件，发现里面的Orders成了这模样了,神奇了？

反编译后的代码

public class Orders

{

// Methods

static Orders()

{

if (!~PostSharp~Laos~Implementation.initialized)

{

LaosNotInitializedException.Throw();

}

~PostSharp~Laos~Implementation.~targetMethod~1 = methodof(Orders.Add);

~PostSharp~Laos~Implementation.~aspect~1.RuntimeInitialize(~PostSharp~Laos~Implementation.~targetMethod~1);

~PostSharp~Laos~Implementation.~targetMethod~5 = methodof(Orders.Delete);

~PostSharp~Laos~Implementation.~aspect~5.RuntimeInitialize(~PostSharp~Laos~Implementation.~targetMethod~5);

~PostSharp~Laos~Implementation.~targetMethod~4 = methodof(Orders.Delete);

~PostSharp~Laos~Implementation.~aspect~4.RuntimeInitialize(~PostSharp~Laos~Implementation.~targetMethod~4);

~PostSharp~Laos~Implementation.~targetMethod~3 = methodof(Orders.Add);

~PostSharp~Laos~Implementation.~aspect~3.RuntimeInitialize(~PostSharp~Laos~Implementation.~targetMethod~3);

~PostSharp~Laos~Implementation.~targetMethod~2 = methodof(Orders.Delete);

~PostSharp~Laos~Implementation.~aspect~2.RuntimeInitialize(~PostSharp~Laos~Implementation.~targetMethod~2);

}

private bool ~Delete(string id)

{

Console.WriteLine("您删除订单成功：编号：{0}", id);

return true;

}

public bool Add(string id, string orderName)

{

bool ~returnValue~1;

MethodExecutionEventArgs ~laosEventArgs~7;

try

{

object[] ~arguments~6 = new object[] { id, orderName };

~laosEventArgs~7 = new MethodExecutionEventArgs(methodof(Orders.Add, Orders), this, ~arguments~6);

~PostSharp~Laos~Implementation.~aspect~1.OnEntry(~laosEventArgs~7);

if (~laosEventArgs~7.FlowBehavior == FlowBehavior.Return)

{

return (bool) ~laosEventArgs~7.ReturnValue;

}

try

{

Console.WriteLine("正在执行新增订单方法的操作，回车继续……");

Console.ReadLine();

Console.WriteLine("您添加订单成功：编号：{0}，名称：{1}", id, orderName);

~returnValue~1 = true;

}

catch (Exception ~exception~2)

{

object[] ~arguments~3 = new object[] { id, orderName };

MethodExecutionEventArgs ~laosEventArgs~4 = new MethodExecutionEventArgs(methodof(Orders.Add, Orders), this, ~arguments~3);

~laosEventArgs~4.Exception = ~exception~2;

~PostSharp~Laos~Implementation.~aspect~3.OnException(~laosEventArgs~4);

switch (~laosEventArgs~4.FlowBehavior)

{

case FlowBehavior.Continue:

goto Label_0145;

case FlowBehavior.Return:

~returnValue~1 = (bool) ~laosEventArgs~4.ReturnValue;

goto Label_0145;

}

throw;

}

Label_0145:

~laosEventArgs~7.ReturnValue = ~returnValue~1;

~PostSharp~Laos~Implementation.~aspect~1.OnSuccess(~laosEventArgs~7);

~returnValue~1 = (bool) ~laosEventArgs~7.ReturnValue;

}

catch (Exception ~exception~5)

{

~laosEventArgs~7.Exception = ~exception~5;

~PostSharp~Laos~Implementation.~aspect~1.OnException(~laosEventArgs~7);

switch (~laosEventArgs~7.FlowBehavior)

{

case FlowBehavior.Continue:

return ~returnValue~1;

case FlowBehavior.Return:

return (bool) ~laosEventArgs~7.ReturnValue;

}

throw;

}

finally

{

~laosEventArgs~7.ReturnValue = ~returnValue~1;

~PostSharp~Laos~Implementation.~aspect~1.OnExit(~laosEventArgs~7);

~returnValue~1 = (bool) ~laosEventArgs~7.ReturnValue;

}

return ~returnValue~1;

}

[DebuggerNonUserCode]

public bool Delete(string id)

{

bool ~returnValue~2;

MethodExecutionEventArgs ~laosEventArgs~8;

try

{

object[] ~arguments~7 = new object[] { id };

~laosEventArgs~8 = new MethodExecutionEventArgs(methodof(Orders.Delete, Orders), this, ~arguments~7);

~PostSharp~Laos~Implementation.~aspect~2.OnEntry(~laosEventArgs~8);

if (~laosEventArgs~8.FlowBehavior == FlowBehavior.Return)

{

return (bool) ~laosEventArgs~8.ReturnValue;

}

try

{

Delegate delegateInstance = new ~PostSharp~Laos~Implementation.~delegate~0(this.~Delete);

object[] arguments = new object[] { id };

MethodInvocationEventArgs eventArgs = new MethodInvocationEventArgs(delegateInstance, arguments);

~PostSharp~Laos~Implementation.~aspect~5.OnInvocation(eventArgs);

~returnValue~2 = (bool) eventArgs.ReturnValue;

}

catch (Exception ~exception~3)

{

object[] ~arguments~4 = new object[] { id };

MethodExecutionEventArgs ~laosEventArgs~5 = new MethodExecutionEventArgs(methodof(Orders.Delete, Orders), this, ~arguments~4);

~laosEventArgs~5.Exception = ~exception~3;

~PostSharp~Laos~Implementation.~aspect~4.OnException(~laosEventArgs~5);

switch (~laosEventArgs~5.FlowBehavior)

{

case FlowBehavior.Continue:

goto Label_0160;

case FlowBehavior.Return:

~returnValue~2 = (bool) ~laosEventArgs~5.ReturnValue;

goto Label_0160;

}

throw;

}

Label_0160:

~laosEventArgs~8.ReturnValue = ~returnValue~2;

~PostSharp~Laos~Implementation.~aspect~2.OnSuccess(~laosEventArgs~8);

~returnValue~2 = (bool) ~laosEventArgs~8.ReturnValue;

}

catch (Exception ~exception~6)

{

~laosEventArgs~8.Exception = ~exception~6;

~PostSharp~Laos~Implementation.~aspect~2.OnException(~laosEventArgs~8);

switch (~laosEventArgs~8.FlowBehavior)

{

case FlowBehavior.Continue:

return ~returnValue~2;

case FlowBehavior.Return:

return (bool) ~laosEventArgs~8.ReturnValue;

}

throw;

}

finally

{

~laosEventArgs~8.ReturnValue = ~returnValue~2;

~PostSharp~Laos~Implementation.~aspect~2.OnExit(~laosEventArgs~8);

~returnValue~2 = (bool) ~laosEventArgs~8.ReturnValue;

}

return ~returnValue~2;

}

}

代码很简单，我是采用控制台应用实现的，如果您有兴趣，请下载Demo源码玩玩。