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; }
运行后会指定创建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。
