1.首先拿到javac文件 例如:test.class
2.可以使用文本编辑器用二进制的方式打开（）
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3.在cmd命令行里使用javap 工具反编译test.class文件为汇编（javap命令：主要用于根据Java字节码文件反汇编为Java源代码文件）
javap -v Test.class > Test.txt
➜ ~ java -version java version "1.8.0_144" Java(TM) SE Runtime Environment (build 1.8.0_144-b01) Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode) ➜ ~ ➜ ~ ➜ ~ cd /Users/shiwen/IdeaProjects/springcloud/example-springcloud-provider/target/classes/com/example/springcloud/provider/hello/ ➜ hello git:(master) ✗ ll total 8 -rw-r--r-- 1 shiwen staff 1.9K 10 11 13:06 HelloController.class ➜ hello git:(master) ✗ javap -v HelloController.class Classfile /Users/shiwen/IdeaProjects/springcloud/example-springcloud-provider/target/classes/com/example/springcloud/provider/hello/HelloController.class Last modified 2017-10-11; size 1965 bytes MD5 checksum b2b6778d4662b520c0b210239844a73a Compiled from "HelloController.java" public class com.example.springcloud.provider.hello.HelloController minor version: 0 major version: 52 flags: ACC_PUBLIC, ACC_SUPER Constant pool: #1 = Methodref #18.#50 // java/lang/Object."<init>":()V #2 = Fieldref #16.#51 // com/example/springcloud/provider/hello/HelloController.client:Lorg/springframework/cloud/client/discovery/DiscoveryClient; #3 = InterfaceMethodref #52.#53 // org/springframework/cloud/client/discovery/DiscoveryClient.getLocalServiceInstance:()Lorg/springframework/cloud/client/ServiceInstance; #4 = Class #54 // java/lang/StringBuilder #5 = Methodref #4.#50 // java/lang/StringBuilder."<init>":()V #6 = String #55 // hello,success!host= #7 = Methodref #4.#56 // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; #8 = InterfaceMethodref #57.#58 // org/springframework/cloud/client/ServiceInstance.getHost:()Ljava/lang/String; #9 = String #59 // ,serviceId= #10 = InterfaceMethodref #57.#60 // org/springframework/cloud/client/ServiceInstance.getServiceId:()Ljava/lang/String; #11 = Methodref #4.#61 // java/lang/StringBuilder.toString:()Ljava/lang/String; #12 = Fieldref #16.#62 // com/example/springcloud/provider/hello/HelloController.logger:Lorg/slf4j/Logger; #13 = InterfaceMethodref #63.#64 // org/slf4j/Logger.info:(Ljava/lang/String;)V #14 = String #65 // hello #15 = String #66 // ，this is first messge #16 = Class #67 // com/example/springcloud/provider/hello/HelloController #17 = Methodref #68.#69 // org/slf4j/LoggerFactory.getLogger:(Ljava/lang/Class;)Lorg/slf4j/Logger; #18 = Class #70 // java/lang/Object #19 = Utf8 logger #20 = Utf8 Lorg/slf4j/Logger; #21 = Utf8 client #22 = Utf8 Lorg/springframework/cloud/client/discovery/DiscoveryClient; #23 = Utf8 RuntimeVisibleAnnotations #24 = Utf8 Lorg/springframework/beans/factory/annotation/Autowired; #25 = Utf8 <init> #26 = Utf8 ()V #27 = Utf8 Code #28 = Utf8 LineNumberTable #29 = Utf8 LocalVariableTable #30 = Utf8 this #31 = Utf8 Lcom/example/springcloud/provider/hello/HelloController; #32 = Utf8 index #33 = Utf8 ()Ljava/lang/String; #34 = Utf8 instance #35 = Utf8 Lorg/springframework/cloud/client/ServiceInstance; #36 = Utf8 hello #37 = Utf8 Ljava/lang/String; #38 = Utf8 Lorg/springframework/web/bind/annotation/RequestMapping; #39 = Utf8 value #40 = Utf8 / #41 = Utf8 (Ljava/lang/String;)Ljava/lang/String; #42 = Utf8 name #43 = Utf8 /hello #44 = Utf8 RuntimeVisibleParameterAnnotations #45 = Utf8 Lorg/springframework/web/bind/annotation/RequestParam; #46 = Utf8 <clinit> #47 = Utf8 SourceFile #48 = Utf8 HelloController.java #49 = Utf8 Lorg/springframework/web/bind/annotation/RestController; #50 = NameAndType #25:#26 // "<init>":()V #51 = NameAndType #21:#22 // client:Lorg/springframework/cloud/client/discovery/DiscoveryClient; #52 = Class #71 // org/springframework/cloud/client/discovery/DiscoveryClient #53 = NameAndType #72:#73 // getLocalServiceInstance:()Lorg/springframework/cloud/client/ServiceInstance; #54 = Utf8 java/lang/StringBuilder #55 = Utf8 hello,success!host= #56 = NameAndType #74:#75 // append:(Ljava/lang/String;)Ljava/lang/StringBuilder; #57 = Class #76 // org/springframework/cloud/client/ServiceInstance #58 = NameAndType #77:#33 // getHost:()Ljava/lang/String; #59 = Utf8 ,serviceId= #60 = NameAndType #78:#33 // getServiceId:()Ljava/lang/String; #61 = NameAndType #79:#33 // toString:()Ljava/lang/String; #62 = NameAndType #19:#20 // logger:Lorg/slf4j/Logger; #63 = Class #80 // org/slf4j/Logger #64 = NameAndType #81:#82 // info:(Ljava/lang/String;)V #65 = Utf8 hello #66 = Utf8 ，this is first messge #67 = Utf8 com/example/springcloud/provider/hello/HelloController #68 = Class #83 // org/slf4j/LoggerFactory #69 = NameAndType #84:#85 // getLogger:(Ljava/lang/Class;)Lorg/slf4j/Logger; #70 = Utf8 java/lang/Object #71 = Utf8 org/springframework/cloud/client/discovery/DiscoveryClient #72 = Utf8 getLocalServiceInstance #73 = Utf8 ()Lorg/springframework/cloud/client/ServiceInstance; #74 = Utf8 append #75 = Utf8 (Ljava/lang/String;)Ljava/lang/StringBuilder; #76 = Utf8 org/springframework/cloud/client/ServiceInstance #77 = Utf8 getHost #78 = Utf8 getServiceId #79 = Utf8 toString #80 = Utf8 org/slf4j/Logger #81 = Utf8 info #82 = Utf8 (Ljava/lang/String;)V #83 = Utf8 org/slf4j/LoggerFactory #84 = Utf8 getLogger #85 = Utf8 (Ljava/lang/Class;)Lorg/slf4j/Logger; { public com.example.springcloud.provider.hello.HelloController(); descriptor: ()V flags: ACC_PUBLIC Code: stack=1, locals=1, args_size=1 0: aload_0 1: invokespecial #1 // Method java/lang/Object."<init>":()V 4: return LineNumberTable: line 13: 0 LocalVariableTable: Start Length Slot Name Signature 0 5 0 this Lcom/example/springcloud/provider/hello/HelloController; public java.lang.String index(); descriptor: ()Ljava/lang/String; flags: ACC_PUBLIC Code: stack=2, locals=3, args_size=1 0: aload_0 1: getfield #2 // Field client:Lorg/springframework/cloud/client/discovery/DiscoveryClient; 4: invokeinterface #3, 1 // InterfaceMethod org/springframework/cloud/client/discovery/DiscoveryClient.getLocalServiceInstance:()Lorg/springframework/cloud/client/ServiceInstance; 9: astore_1 10: new #4 // class java/lang/StringBuilder 13: dup 14: invokespecial #5 // Method java/lang/StringBuilder."<init>":()V 17: ldc #6 // String hello,success!host= 19: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 22: aload_1 23: invokeinterface #8, 1 // InterfaceMethod org/springframework/cloud/client/ServiceInstance.getHost:()Ljava/lang/String; 28: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 31: ldc #9 // String ,serviceId= 33: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 36: aload_1 37: invokeinterface #10, 1 // InterfaceMethod org/springframework/cloud/client/ServiceInstance.getServiceId:()Ljava/lang/String; 42: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 45: invokevirtual #11 // Method java/lang/StringBuilder.toString:()Ljava/lang/String; 48: astore_2 49: getstatic #12 // Field logger:Lorg/slf4j/Logger; 52: aload_2 53: invokeinterface #13, 2 // InterfaceMethod org/slf4j/Logger.info:(Ljava/lang/String;)V 58: aload_2 59: areturn LineNumberTable: line 22: 0 line 23: 10 line 24: 49 line 25: 58 LocalVariableTable: Start Length Slot Name Signature 0 60 0 this Lcom/example/springcloud/provider/hello/HelloController; 10 50 1 instance Lorg/springframework/cloud/client/ServiceInstance; 49 11 2 hello Ljava/lang/String; RuntimeVisibleAnnotations: 0: #38(#39=[s#40]) public java.lang.String hello(java.lang.String); descriptor: (Ljava/lang/String;)Ljava/lang/String; flags: ACC_PUBLIC Code: stack=2, locals=2, args_size=2 0: new #4 // class java/lang/StringBuilder 3: dup 4: invokespecial #5 // Method java/lang/StringBuilder."<init>":()V 7: ldc #14 // String hello 9: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 12: aload_1 13: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 16: ldc #15 // String ，this is first messge 18: invokevirtual #7 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 21: invokevirtual #11 // Method java/lang/StringBuilder.toString:()Ljava/lang/String; 24: areturn LineNumberTable: line 31: 0 LocalVariableTable: Start Length Slot Name Signature 0 25 0 this Lcom/example/springcloud/provider/hello/HelloController; 0 25 1 name Ljava/lang/String; RuntimeVisibleAnnotations: 0: #38(#39=[s#43]) RuntimeVisibleParameterAnnotations: parameter 0: 0: #45() static {}; descriptor: ()V flags: ACC_STATIC Code: stack=1, locals=0, args_size=0 0: ldc #16 // class com/example/springcloud/provider/hello/HelloController 2: invokestatic #17 // Method org/slf4j/LoggerFactory.getLogger:(Ljava/lang/Class;)Lorg/slf4j/Logger; 5: putstatic #12 // Field logger:Lorg/slf4j/Logger; 8: return LineNumberTable: line 14: 0 } SourceFile: "HelloController.java" RuntimeVisibleAnnotations: 0: #49()