AOP有幾種實現方式？

原創

2020-07-12 14:23

\n /// Created on demand before each generation pass\n ///

\n class SyntaxReceiver : ISyntaxReceiver\n {\n public List CandidateFields { get; } = new List();\n\n ///

\n /// Called for every syntax node in the compilation, we can inspect the nodes and save any information useful for generation\n ///

\n public void OnVisitSyntaxNode(SyntaxNode syntaxNode)\n {\n // any field with at least one attribute is a candidate for property generation\n if (syntaxNode is FieldDeclarationSyntax fieldDeclarationSyntax\n && fieldDeclarationSyntax.AttributeLists.Count > 0)\n {\n CandidateFields.Add(fieldDeclarationSyntax);\n }\n }\n }\n }\n}"}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"2.1.2 修改代碼"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"代碼文件修改"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一般來說，很少有這樣實現的，代碼文件都改了，我們碼農還怎麼寫bug呀。"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"中間語言修改"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"有很多語言編譯的結果並不是直接的機器碼，而是優化後的一個接近底層的中間層語言，方便擴展支持不同cpu，不同機器架構。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比如 dotnet 的 IL "}]},{"type":"codeblock","attrs":{"lang":"csharp"},"content":[{"type":"text","text":".class private auto ansi ''\n{\n} // end of class \n\n.class public auto ansi beforefieldinit C\n extends [mscorlib]System.Object\n{\n // Fields\n .field private initonly int32 'k__BackingField'\n .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (\n 01 00 00 00\n )\n\n // Methods\n .method public hidebysig specialname rtspecialname \n instance void .ctor () cil managed \n {\n // Method begins at RVA 0x2050\n // Code size 21 (0x15)\n .maxstack 8\n\n IL_0000: ldarg.0\n IL_0001: ldc.i4.5\n IL_0002: stfld int32 C::'k__BackingField'\n IL_0007: ldarg.0\n IL_0008: call instance void [mscorlib]System.Object::.ctor()\n IL_000d: ldarg.0\n IL_000e: ldc.i4.4\n IL_000f: stfld int32 C::'k__BackingField'\n IL_0014: ret\n } // end of method C::.ctor\n\n .method public hidebysig specialname \n instance int32 get_x () cil managed \n {\n .custom instance void [mscorlib]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = (\n 01 00 00 00\n )\n // Method begins at RVA 0x2066\n // Code size 7 (0x7)\n .maxstack 8\n\n IL_0000: ldarg.0\n IL_0001: ldfld int32 C::'k__BackingField'\n IL_0006: ret\n } // end of method C::get_x\n\n // Properties\n .property instance int32 x()\n {\n .get instance int32 C::get_x()\n }\n\n} // end of class C\n\n"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比如 java 的字節碼（反編譯的結果）"}]},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"Classfile /E:/JavaCode/TestProj/out/production/TestProj/com/rhythm7/Main.class\n Last modified 2018-4-7; size 362 bytes\n MD5 checksum 4aed8540b098992663b7ba08c65312de\n Compiled from \"Main.java\"\npublic class com.rhythm7.Main\n minor version: 0\n major version: 52\n flags: ACC_PUBLIC, ACC_SUPER\nConstant pool:\n #1 = Methodref #4.#18 // java/lang/Object.\"\":()V\n #2 = Fieldref #3.#19 // com/rhythm7/Main.m:I\n #3 = Class #20 // com/rhythm7/Main\n #4 = Class #21 // java/lang/Object\n #5 = Utf8 m\n #6 = Utf8 I\n #7 = Utf8 \n #8 = Utf8 ()V\n #9 = Utf8 Code\n #10 = Utf8 LineNumberTable\n #11 = Utf8 LocalVariableTable\n #12 = Utf8 this\n #13 = Utf8 Lcom/rhythm7/Main;\n #14 = Utf8 inc\n #15 = Utf8 ()I\n #16 = Utf8 SourceFile\n #17 = Utf8 Main.java\n #18 = NameAndType #7:#8 // \"\":()V\n #19 = NameAndType #5:#6 // m:I\n #20 = Utf8 com/rhythm7/Main\n #21 = Utf8 java/lang/Object\n{\n private int m;\n descriptor: I\n flags: ACC_PRIVATE\n\n public com.rhythm7.Main();\n descriptor: ()V\n flags: ACC_PUBLIC\n Code:\n stack=1, locals=1, args_size=1\n 0: aload_0\n 1: invokespecial #1 // Method java/lang/Object.\"\":()V\n 4: return\n LineNumberTable:\n line 3: 0\n LocalVariableTable:\n Start Length Slot Name Signature\n 0 5 0 this Lcom/rhythm7/Main;\n\n public int inc();\n descriptor: ()I\n flags: ACC_PUBLIC\n Code:\n stack=2, locals=1, args_size=1\n 0: aload_0\n 1: getfield #2 // Field m:I\n 4: iconst_1\n 5: iadd\n 6: ireturn\n LineNumberTable:\n line 8: 0\n LocalVariableTable:\n Start Length Slot Name Signature\n 0 7 0 this Lcom/rhythm7/Main;\n}\nSourceFile: \"Main.java\""}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"它們也是編程語言的一種，也是可以寫的，所以我們可以用來把別人方法體改了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"當然怎麼改，怎麼改得各種各樣方法都兼容，做的人簡直👍"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong"}],"text":"生成代理代碼"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"不修改原來的代碼文件，新增代理代碼實現"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":1,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"不修改編譯好的IL 或字節碼等，往裏面添加IL或字節碼等形式代理代碼"}]}]}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"2.1.3 利用編譯器或者運行時的功能"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一般來說，也是利用編譯器自身提供得擴展功能做擴展"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"java的 AspectJ 好像就可以利用了ajc編譯器做事情"}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"2.1.4 利用運行時功能"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"理論上 dotnet 也可以實現CLR Profiling API 在JIT編譯時修改method body。實現真正無任何限制的運行時靜態AOP （不過貌似得用C++才能做CLR Profiling API，文檔少，兼容貌似也挺難做的）"}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"2.2 按照編織時機"}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"2.2.1 編譯前"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比如"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"修改掉別人的代碼文件"},{"type":"text","marks":[{"type":"italic"},{"type":"del"}],"text":"（找死）"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"生成新的代碼，讓編譯器編譯進去，運行時想辦法用新的代碼"}]}]}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"2.2.2 編譯時"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"元編程"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"做個編譯器"}]}]}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"2.2.3 編譯後靜態編織一次"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"根據編譯好的東西（dotnet的dll或者其他語言的東西）利用反射，解析等技術生成代理實現，然後塞進去"}]}]}]},{"type":"heading","attrs":{"align":null,"level":4},"content":[{"type":"text","text":"2.2.4 運行時"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"嚴格來說，運行時也是編譯後"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"不過不是再編織一次，而是每次運行都編織"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"並且沒有什麼前中後了，"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"都是程序啓動後，在具體類執行之前，把這個類編織了"}]},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比如java 的類加載器：在目標類被裝載到JVM時，通過一個特殊的類加載器，對目標類的字節碼重新“增強。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"具有aop功能的各類 IOC 容器在生成實例前創建代理實例"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"其實也可以在註冊IOC容器時替換爲代理類型"}]}]}]},{"type":"heading","attrs":{"align":null,"level":1},"content":[{"type":"text","text":"3. 代理"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"這裏單獨再說一下代理是什麼，"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"畢竟很多AOP框架或者其他框架都有利用代理的思想，"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"爲什麼都要這樣玩呢？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"很簡單，代理就是幫你做相同事情，並且可以比你做的更多，還一點兒都不動到你原來的代碼。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"比如如下真實的class 和代理class 看起來一模一樣"}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/3d/3dc1cede74ab1f4aeaf29cdb2c0bc613.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"但兩者的真實的代碼可能是這樣子的"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"RealClass:"}]},{"type":"codeblock","attrs":{"lang":"csharp"},"content":[{"type":"text","text":"public class RealClass\n{\n public virtual int Add(int i, int j)\n {\n return i + j;\n }\n}"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ProxyClass:"}]},{"type":"codeblock","attrs":{"lang":"csharp"},"content":[{"type":"text","text":"public class ProxyClass : RealClass\n{\n public override int Add(int i, int j)\n {\n int r = 0;\n i += 7;\n j -= 7;\n r = base.Add(i, j);\n r += 55;\n return r;\n }\n}"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"所以我們調用的時候會是這樣"}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/d3/d3daa39e6b7a52fe41b6f457658cf8e7.png","alt":null,"title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下一篇介紹一下 Roslyn 的 source generator 怎麼做Aop"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}}]}