Rougamo、Fody 实现静态Aop
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-instancetradedoccodedatadata" 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。
