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Rougamo、Fody 实现静态Aop

发表于阅读(1) 博客类别：Crawler 转自：https://www.cnblogs.com/KarlAlbright/p/18277740
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最近在看项目，看到别人使用Rougamo框架，好奇花了点时间仔细研究了，在这里记录一下。

0. 静态编织 Aop

首先，我们先了解什么是Aop? Aop 是指面向切面编程 (Aspect Oriented Programming)，而所谓的切面，可以认为是具体拦截的某个业务点。

我们常用的aop框架是 AspectCore，他是属于动态代理，也就是发生在运行时期间对代码进行“修改”。

Rougamo、Fody 是属于静态编织，是指在编译阶段将代码修改或额外的功能直接嵌入到程序集中，这个过程发生在源代码被编译成可执行文件或库之前。这意味着，一旦编译完成，插入的代码就已经是程序集的一部分，无需在运行时再进行额外的操作。

1. Rougamo 肉夹馍

Rougamo 是一个开源项目，github: https://github.com/inversionhourglass/Rougamo，他是通过Fody -> Mono.Cecil 的方式实现静态编织实现Aop功能。

创建控制台程序，Nuget安装 Rougamo.Fody

[AttributeUsage(AttributeTargets.Method)]
public class LoggingAttribute : MoAttribute
{
    public override void OnEntry(MethodContext context)
    {
        Console.WriteLine("执行方法 {0}() 开始，参数：{1}.", context.Method.Name, 
            JsonConvert.SerializeObject(context.Arguments));
    }
    public override void OnException(MethodContext context)
    {
        Console.WriteLine("执行方法 {0}() 异常，{1}.", context.Method.Name, context.Exception.Message);
    }
    public override void OnExit(MethodContext context)
    {
        Console.WriteLine("执行方法 {0}() 结束.", context.Method.Name);
    }
    public override void OnSuccess(MethodContext context)
    {
        Console.WriteLine("执行方法 {0}() 成功.", context.Method.Name);
    }
}
internal class Program
{
    static void Main(string[] args)
    {
        Add(1, 2);
        AddAsync(1, 2);
        Divide(1, 2);
    }

    [Logging]
    static int Add(int a, int b) => a + b;

    [Logging]
    static Task<int> AddAsync(int a, int b) => Task.FromResult(a + b);

    [Logging]
    static decimal Divide(decimal a, decimal b) => a / b;
}

运行后会自动创建FodyWeavers.xsd 和 FodyWeavers.xml

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <!-- This file was generated by Fody. Manual changes to this file will be lost when your project is rebuilt. -->
  <xs:element name="Weavers">
    <xs:complexType>
      <xs:all>
        <xs:element name="Rougamo" minOccurs="0" maxOccurs="1" type="xs:anyType" />
      </xs:all>
      <xs:attribute name="VerifyAssembly" type="xs:boolean">
        <xs:annotation>
          <xs:documentation>'true' to run assembly verification (PEVerify) on the target assembly after all weavers have been executed.</xs:documentation>
        </xs:annotation>
      </xs:attribute>
      <xs:attribute name="VerifyIgnoreCodes" type="xs:string">
        <xs:annotation>
          <xs:documentation>A comma-separated list of error codes that can be safely ignored in assembly verification.</xs:documentation>
        </xs:annotation>
      </xs:attribute>
      <xs:attribute name="GenerateXsd" type="xs:boolean">
        <xs:annotation>
          <xs:documentation>'false' to turn off automatic generation of the XML Schema file.</xs:documentation>
        </xs:annotation>
      </xs:attribute>
    </xs:complexType>
  </xs:element>
</xs:schema>

<Weavers xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="FodyWeavers.xsd">
  <Rougamo />
</Weavers>

下面是运行结果

这时候我们可以看到增加了LoggingAttribute 特性的方法在运行前、运行成功、运行结束执行了 OnEntry(MethodContext context) 、OnSuccess(MethodContext context)、OnExit(MethodContext context) 方法，这时我们打开ILSpy工具，看看实际运行的代码

internal class Program
{
    private static void Main(string[] args)
    {
        Add(1, 2);
        AddAsync(1, 2);
        Divide(1m, 2m);
    }

    [DebuggerStepThrough]
    private static int Add(int a, int b)
    {
        LoggingAttribute loggingAttribute = new LoggingAttribute();
        IMo[] mos = new IMo[1] { loggingAttribute };
        MethodContext methodContext = new MethodContext(null, typeof(Program), MethodBase.GetMethodFromHandle((RuntimeMethodHandle)/*OpCode not supported: LdMemberToken*/, typeof(Program).TypeHandle), isAsync: false, isIterator: false, mosNonEntryFIFO: false, mos, new object[2] { a, b });
        loggingAttribute.OnEntry(methodContext);
        int result = default(int);
        if (methodContext.ReturnValueReplaced)
        {
            result = (int)methodContext.ReturnValue;
            loggingAttribute.OnExit(methodContext);
            return result;
        }
        if (methodContext.RewriteArguments)
        {
            a = (int)methodContext.Arguments[0];
            b = (int)methodContext.Arguments[1];
        }
        bool flag = default(bool);
        do
        {
            try
            {
                while (true)
                {
                    try
                    {
                        flag = false;
                        result = $Rougamo_Add(a, b);
                    }
                    catch (Exception exception)
                    {
                        methodContext.Exception = exception;
                        methodContext.Arguments[0] = a;
                        methodContext.Arguments[1] = b;
                        loggingAttribute.OnException(methodContext);
                        if (methodContext.RetryCount > 0)
                        {
                            continue;
                        }
                        if (methodContext.ExceptionHandled)
                        {
                            result = (int)methodContext.ReturnValue;
                            break;
                        }
                        throw;
                    }
                    break;
                }
            }
            finally
            {
                if (methodContext.HasException || methodContext.ExceptionHandled)
                {
                    goto IL_0160;
                }
                methodContext.ReturnValue = result;
                methodContext.Arguments[0] = a;
                methodContext.Arguments[1] = b;
                loggingAttribute.OnSuccess(methodContext);
                if (methodContext.RetryCount <= 0)
                {
                    if (methodContext.ReturnValueReplaced)
                    {
                        result = (int)methodContext.ReturnValue;
                    }
                    goto IL_0160;
                }
                flag = true;
                goto end_IL_00fc;
                IL_0160:
                loggingAttribute.OnExit(methodContext);
                end_IL_00fc:;
            }
        }
        while (flag);
        return result;
    }

    [DebuggerStepThrough]
    private static Task<int> AddAsync(int a, int b)
    {
        LoggingAttribute loggingAttribute = new LoggingAttribute();
        IMo[] mos = new IMo[1] { loggingAttribute };
        MethodContext methodContext = new MethodContext(null, typeof(Program), MethodBase.GetMethodFromHandle((RuntimeMethodHandle)/*OpCode not supported: LdMemberToken*/, typeof(Program).TypeHandle), isAsync: false, isIterator: false, mosNonEntryFIFO: false, mos, new object[2] { a, b });
        loggingAttribute.OnEntry(methodContext);
        Task<int> result = default(Task<int>);
        if (methodContext.ReturnValueReplaced)
        {
            result = (Task<int>)methodContext.ReturnValue;
            loggingAttribute.OnExit(methodContext);
            return result;
        }
        if (methodContext.RewriteArguments)
        {
            a = (int)methodContext.Arguments[0];
            b = (int)methodContext.Arguments[1];
        }
        bool flag = default(bool);
        do
        {
            try
            {
                while (true)
                {
                    try
                    {
                        flag = false;
                        result = $Rougamo_AddAsync(a, b);
                    }
                    catch (Exception exception)
                    {
                        methodContext.Exception = exception;
                        methodContext.Arguments[0] = a;
                        methodContext.Arguments[1] = b;
                        loggingAttribute.OnException(methodContext);
                        if (methodContext.RetryCount > 0)
                        {
                            continue;
                        }
                        if (methodContext.ExceptionHandled)
                        {
                            result = (Task<int>)methodContext.ReturnValue;
                            break;
                        }
                        throw;
                    }
                    break;
                }
            }
            finally
            {
                if (methodContext.HasException || methodContext.ExceptionHandled)
                {
                    goto IL_015b;
                }
                methodContext.ReturnValue = result;
                methodContext.Arguments[0] = a;
                methodContext.Arguments[1] = b;
                loggingAttribute.OnSuccess(methodContext);
                if (methodContext.RetryCount <= 0)
                {
                    if (methodContext.ReturnValueReplaced)
                    {
                        result = (Task<int>)methodContext.ReturnValue;
                    }
                    goto IL_015b;
                }
                flag = true;
                goto end_IL_00fc;
                IL_015b:
                loggingAttribute.OnExit(methodContext);
                end_IL_00fc:;
            }
        }
        while (flag);
        return result;
    }

    [DebuggerStepThrough]
    private static decimal Divide(decimal a, decimal b)
    {
        LoggingAttribute loggingAttribute = new LoggingAttribute();
        IMo[] mos = new IMo[1] { loggingAttribute };
        MethodContext methodContext = new MethodContext(null, typeof(Program), MethodBase.GetMethodFromHandle((RuntimeMethodHandle)/*OpCode not supported: LdMemberToken*/, typeof(Program).TypeHandle), isAsync: false, isIterator: false, mosNonEntryFIFO: false, mos, new object[2] { a, b });
        loggingAttribute.OnEntry(methodContext);
        decimal result = default(decimal);
        if (methodContext.ReturnValueReplaced)
        {
            result = (decimal)methodContext.ReturnValue;
            loggingAttribute.OnExit(methodContext);
            return result;
        }
        if (methodContext.RewriteArguments)
        {
            a = (decimal)methodContext.Arguments[0];
            b = (decimal)methodContext.Arguments[1];
        }
        bool flag = default(bool);
        do
        {
            try
            {
                while (true)
                {
                    try
                    {
                        flag = false;
                        result = $Rougamo_Divide(a, b);
                    }
                    catch (Exception exception)
                    {
                        methodContext.Exception = exception;
                        methodContext.Arguments[0] = a;
                        methodContext.Arguments[1] = b;
                        loggingAttribute.OnException(methodContext);
                        if (methodContext.RetryCount > 0)
                        {
                            continue;
                        }
                        if (methodContext.ExceptionHandled)
                        {
                            result = (decimal)methodContext.ReturnValue;
                            break;
                        }
                        throw;
                    }
                    break;
                }
            }
            finally
            {
                if (methodContext.HasException || methodContext.ExceptionHandled)
                {
                    goto IL_0160;
                }
                methodContext.ReturnValue = result;
                methodContext.Arguments[0] = a;
                methodContext.Arguments[1] = b;
                loggingAttribute.OnSuccess(methodContext);
                if (methodContext.RetryCount <= 0)
                {
                    if (methodContext.ReturnValueReplaced)
                    {
                        result = (decimal)methodContext.ReturnValue;
                    }
                    goto IL_0160;
                }
                flag = true;
                goto end_IL_00fc;
                IL_0160:
                loggingAttribute.OnExit(methodContext);
                end_IL_00fc:;
            }
        }
        while (flag);
        return result;
    }

    [Logging]
    private static int $Rougamo_Add(int a, int b)
    {
        return a + b;
    }

    [Logging]
    private static Task<int> $Rougamo_AddAsync(int a, int b)
    {
        return Task.FromResult(a + b);
    }

    [Logging]
    private static decimal $Rougamo_Divide(decimal a, decimal b)
    {
        return a / b;
    }
}

从实际运行的代码我们可以看到，原先Add(int a, int b)方法中的执行内容被移动到 $Rougamo_Add方法中，而Add(int a, int b)方法先是new LoggingAttribute() 和 new Rougamo.Context.MethodContext() -> 执行了 loggingAttribute.OnEntry(methodContext); -> 在do{}while(bool) 执行了$Rougamo_Add(a, b); -> 在 exception 中执行了loggingAttribute.OnException(methodContext); -> 在 finally中执行了 loggingAttribute.OnSuccess(methodContext); 和 loggingAttribute.OnExit(methodContext);

注：do{}while(bool) 执行了$Rougamo_Add(a, b); 是因为 Rougamo 可以实现方法执行失败重试功能

至此我们明白了 Rougamo 实现 Aop功能是通过编译时修改IL代码，往代码增加对应的生命周期代码。那他为什么可以做到呢？其实是借用了Fody -> Mono.Cecil 的方式。

代码如下：https://gitee.com/Karl_Albright/csharp-demo/tree/master/FodyDemo/RougamoDemo

2. Fody -> Mono.Cecil

Fody 是一个开源项目，github: https://github.com/Fody/Fody，相关教程文档在 https://github.com/Fody/Home/tree/master/pages

创建类库，选择netstandard2.0，命名为HelloWorld，Nuget安装 Fody 和 FodyPackaging

注：必须创建 netstandard2.0，因为FodyPackaging的目标是netstandard2.0，

在HelloWorld项目中，我们只放 HWAttribute类，继承于 Attribute。代码如下

[AttributeUsage(AttributeTargets.Assembly | AttributeTargets.Module | AttributeTargets.Class | AttributeTargets.Struct | AttributeTargets.Constructor | AttributeTargets.Method | AttributeTargets.Property)]
public class HWAttribute : Attribute
{

}

再次创建类库，选择netstandard2.0，命名为HelloWorld.Fody，Nuget安装 FodyHelpers，引用HelloWorld类库

在HelloWorld.Fody项目中，我们只放ModuleWeaver类（类名是固定的，详情见Fody文档），继承于 BaseModuleWeaver。代码如下

using Fody;
using Mono.Cecil;
using Mono.Cecil.Cil;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;

namespace HelloWorld.Fody
{
    public partial class ModuleWeaver : BaseModuleWeaver
    {
        public override void Execute()
        {
            foreach (var type in ModuleDefinition.Types)
            {
                foreach (var method in type.Methods)
                {
                    var customerAttribute = method.CustomAttributes.FirstOrDefault(x => x.AttributeType.Name == nameof(HWAttribute));
                    if (customerAttribute != null)
                    {
                        ProcessMethod(method);
                    }
                }
            }
        }

        public override IEnumerable<string> GetAssembliesForScanning()
        {
            yield return "mscorlib";
            yield return "System";
        }

        private MethodInfo _writeLineMethod => typeof(Console).GetMethod("WriteLine", new Type[] { typeof(string) });

        private void ProcessMethod(MethodDefinition method)
        {
            // 获取当前方法体中的第一个IL指令
            var processor = method.Body.GetILProcessor();
            var current = method.Body.Instructions.First();

            // 插入一个 Nop 指令，表示什么都不做
            var first = Instruction.Create(OpCodes.Nop);
            processor.InsertBefore(current, first);
            current = first;

            // 构造 Console.WriteLine("Hello World")
            foreach (var instruction in GetInstructions(method))
            {
                processor.InsertAfter(current, instruction);
                current = instruction;
            }
        }
        private IEnumerable<Instruction> GetInstructions(MethodDefinition method)
        {
            yield return Instruction.Create(OpCodes.Nop);
            yield return Instruction.Create(OpCodes.Ldstr, "Hello World.");
            yield return Instruction.Create(OpCodes.Call, ModuleDefinition.ImportReference(_writeLineMethod));
        }
    }
}

在代码中，我们遍历了所有类型的所有方法，如果方法标注了 HWAttribute特性，则增加 Console.WriteLine("Hello World."); 代码。

创建控制台应用程序，命名为HelloWorldFodyDemo，添加 HelloWorld 和 HelloWorld.Fody 项目引用，并且手动增加 WeaverFiles标签，目标是HelloWorld.Fody.dll

在控制台中，我们需要一个方法，方法上有 HWAttribute 特性就可以了，代码如下

internal class Program
{
    static void Main(string[] args)
    {
        Echo();
        Console.ReadKey();
    }

    [HW]
    public static void Echo()
    {
        Console.WriteLine("Hello Fody.");
    }
}

在控制台项目中，我们还需要 FodyWeavers.xml 和 FodyWeavers.xsd 文件，（我也是从上面Rougamo项目中复制的），内容如下

<Weavers xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="FodyWeavers.xsd">
    <HelloWorld />
</Weavers>

<?xml version="1.0" encoding="utf-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="Weavers">
    <xs:complexType>
      <xs:all>
        <xs:element name="HelloWorld" minOccurs="0" maxOccurs="1" type="xs:anyType" />
      </xs:all>
      <xs:attribute name="VerifyAssembly" type="xs:boolean">
        <xs:annotation>
          <xs:documentation>'true' to run assembly verification (PEVerify) on the target assembly after all weavers have been executed.</xs:documentation>
        </xs:annotation>
      </xs:attribute>
      <xs:attribute name="VerifyIgnoreCodes" type="xs:string">
        <xs:annotation>
          <xs:documentation>A comma-separated list of error codes that can be safely ignored in assembly verification.</xs:documentation>
        </xs:annotation>
      </xs:attribute>
      <xs:attribute name="GenerateXsd" type="xs:boolean">
        <xs:annotation>
          <xs:documentation>'false' to turn off automatic generation of the XML Schema file.</xs:documentation>
        </xs:annotation>
      </xs:attribute>
    </xs:complexType>
  </xs:element>
</xs:schema>

目前，文件结构如下

FodyDemo
|--- HelloWorld
     |--- HWAttribute.cs
     |--- HelloWorld.csproj
|--- HelloWorld.Fody
     |--- HelloWorld.Fody.csproj
     |--- ModuleWeaver.cs
|--- HelloWorldFodyDemo
     |--- FodyWeavers.xml
     |--- FodyWeavers.xsd
     |--- HelloWorldFodyDemo.csproj
     |--- Program.cs

代码如下：https://gitee.com/Karl_Albright/csharp-demo/tree/master/FodyDemo

最后运行结果如下，很明显，HWAttribute生效了，我们成功的在Echo()方法前打印了Hello World。

我们再次打开ILSpy工具，得到的结果如图，代码增加了Console.WriteLine("Hello World.");行代码

4. Fody 有很多其他的“插件”，大家可以多试试

AutoProperties.Fody: 这个外接程序为您提供了对自动属性的扩展控制，比如直接访问backing字段或拦截getter和setter。

PropertyChanged.Fody: 将属性通知添加到实现INotifyPropertyChanged的所有类。

InlineIL.Fody: 在编译时注入任意IL代码。

MethodDecorator.Fody：通过IL重写编译时间装饰器模式。

NullGuard.Fody: 将空参数检查添加到程序集。

ToString.Fody: 给属性生成ToString()方法

Rougamo.Fody: 在编译时生效的AOP组件，类似于PostSharp。

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