Kotlin字节码生成机制详尽分析
通过注解修改Kotlin的class文件名:
对于Kotlin文件在编译之后生成的class文件名默认是有一定规则的,比如:
而其实这个生成字节码的文件名称是可以被改的,之前https://www.cnblogs.com/webor2006/p/11530600.html也提及到,也就是可以用JvmName注解,再来试一下:
然后重新的build一次,再来看一下生成的class文件:
既然可以手动的将编译的字符码文件名给改了,那。。如果两个Kotlin文件都指定同一个名称,会有啥情况发生呢?试试,再来建一个Kotlin文件:
那。。有没有一种机制能将这两个类的内容生成到一个HelloWorld.class,当然有,也就是Kotlin中可以将多个Kotlin文件合并成一个字节码文件,下面来看一下:
接下来再次编译:
居然此时就没报错了,那这个字节码文件中的内容是?跟进去瞅一下:
bogon:kotlin_lecture xiongwei$ javap -c -v com/kotlin/test11/HelloWorld.class
Classfile /Users/xiongwei/Documents/workspace/IntelliJSpace/kotlin_lecture/out/production/kotlin_lecture/com/kotlin/test11/HelloWorld.class
Last modified 2019-9-20; size 860 bytes
MD5 checksum 47cd63b80d95d489afa25bedd346da23
public final class com.kotlin.test11.HelloWorld
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_FINAL, ACC_SUPER
Constant pool:
#1 = Utf8 com/kotlin/test11/HelloWorld
#2 = Class #1 // com/kotlin/test11/HelloWorld
#3 = Utf8 java/lang/Object
#4 = Class #3 // java/lang/Object
#5 = Utf8 getMystr
#6 = Utf8 ()Ljava/lang/String;
#7 = Utf8 Lorg/jetbrains/annotations/NotNull;
#8 = Utf8 com/kotlin/test11/HelloWorld__HelloKotlin3Kt
#9 = Class #8 // com/kotlin/test11/HelloWorld__HelloKotlin3Kt
#10 = NameAndType #5:#6 // getMystr:()Ljava/lang/String;
#11 = Methodref #9.#10 // com/kotlin/test11/HelloWorld__HelloKotlin3Kt.getMystr:()Ljava/lang/String;
#12 = Utf8 setMystr
#13 = Utf8 (Ljava/lang/String;)V
#14 = NameAndType #12:#13 // setMystr:(Ljava/lang/String;)V
#15 = Methodref #9.#14 // com/kotlin/test11/HelloWorld__HelloKotlin3Kt.setMystr:(Ljava/lang/String;)V
#16 = Utf8 <set-?>
#17 = Utf8 Ljava/lang/String;
#18 = Utf8 myPrint
#19 = Utf8 ()V
#20 = NameAndType #18:#19 // myPrint:()V
#21 = Methodref #9.#20 // com/kotlin/test11/HelloWorld__HelloKotlin3Kt.myPrint:()V
#22 = Utf8 myPrint2
#23 = Utf8 com/kotlin/test11/HelloWorld__HelloKotlin4Kt
#24 = Class #23 // com/kotlin/test11/HelloWorld__HelloKotlin4Kt
#25 = NameAndType #22:#19 // myPrint2:()V
#26 = Methodref #24.#25 // com/kotlin/test11/HelloWorld__HelloKotlin4Kt.myPrint2:()V
#27 = Utf8 Lkotlin/Metadata;
#28 = Utf8 mv
#29 = Integer 1
#30 = Integer 15
#31 = Utf8 bv
#32 = Integer 0
#33 = Integer 3
#34 = Utf8 k
#35 = Integer 4
#36 = Utf8 d1
#37 = Utf8 Code
#38 = Utf8 LineNumberTable
#39 = Utf8 RuntimeInvisibleAnnotations
#40 = Utf8 LocalVariableTable
#41 = Utf8 RuntimeInvisibleParameterAnnotations
#42 = Utf8 RuntimeVisibleAnnotations
{
public static final java.lang.String getMystr();
descriptor: ()Ljava/lang/String;
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
Code:
stack=1, locals=0, args_size=0
0: invokestatic #11 // Method com/kotlin/test11/HelloWorld__HelloKotlin3Kt.getMystr:()Ljava/lang/String;
3: areturn
LineNumberTable:
line 1: 0
RuntimeInvisibleAnnotations:
0: #7() public static final void setMystr(java.lang.String);
descriptor: (Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokestatic #15 // Method com/kotlin/test11/HelloWorld__HelloKotlin3Kt.setMystr:(Ljava/lang/String;)V
4: return
LineNumberTable:
line 1: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 <set-?> Ljava/lang/String;
RuntimeInvisibleParameterAnnotations:
0:
0: #7() public static final void myPrint();
descriptor: ()V
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
Code:
stack=0, locals=0, args_size=0
0: invokestatic #21 // Method com/kotlin/test11/HelloWorld__HelloKotlin3Kt.myPrint:()V
3: return
LineNumberTable:
line 1: 0 public static final void myPrint2();
descriptor: ()V
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
Code:
stack=0, locals=0, args_size=0
0: invokestatic #26 // Method com/kotlin/test11/HelloWorld__HelloKotlin4Kt.myPrint2:()V
3: return
LineNumberTable:
line 1: 0
}
RuntimeVisibleAnnotations:
0: #27(#28=[I#29,I#29,I#30],#31=[I#29,I#32,I#33],#34=I#35,#36=[s#8,s#23])
很明显字节码中确实是已经包含HelloKotlin3.kt和HelloKotlin4.kt的内容进行了合并了,既然这俩文件最终会编译成一个字节码,那如果在HelloKotlin4.kt中也定义一个跟HelloKotlin3.kt一样的方法名会有啥反应呢,如下:
比较容易理解,还是将其方法名进行还原,接下来新建一个Java文件来调用一下:
@JvmField:
使用@JvmFiled注解对Kotlin中的属性进行标注时,表示它是一个实例字段(instance filed),Kotlin编译器在处理的时候,将不会给这个字段生成getter/setter。
下面先来新建一个类:
接下来咱们可以使用@JvmField注解,如下:
注上它之后,其实该字段就变为了一个实例字段,Kotlin编译器就不会给该字段生成getter和setter了,下面反编译一下:
那。。没法验证所说的理论了呀,这里换一种思路,从Java调用上面来验证:
当然,实际过程中貌似木有必要使用该注解,一般用getter和setter的较大,做个了解。
伴生对像:
关于它其实在之前https://www.cnblogs.com/webor2006/p/11210181.html已经学习过了,这里从Java调用Kotlin的角度再来看一它:
然后再新建一个Java:
完整调用如下:
好,接下来咱们再用一个@JvmField注解:
此时程序调用就得修改为:
接下来再来看一下在伴生对象中定义方法又是如何调用的,如下:
那在字节码中MyClass2是如何定义的呢?反编译一下,之前反编译乱码了,下面用javap -v来看一下:
bogon:kotlin_lecture xiongwei$ javap -verbose com/kotlin/test11/MyClass2.class
Classfile /Users/xiongwei/Documents/workspace/IntelliJSpace/kotlin_lecture/out/production/kotlin_lecture/com/kotlin/test11/MyClass2.class
Last modified 2019-9-21; size 770 bytes
MD5 checksum b7bf58035d08f2c1f25542b389451e7e
Compiled from "HelloKotlin7.kt"
public final class com.kotlin.test11.MyClass2
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_FINAL, ACC_SUPER
Constant pool:
#1 = Utf8 com/kotlin/test11/MyClass2
#2 = Class #1 // com/kotlin/test11/MyClass2
#3 = Utf8 java/lang/Object
#4 = Class #3 // java/lang/Object
#5 = Utf8 <init>
#6 = Utf8 ()V
#7 = NameAndType #5:#6 // "<init>":()V
#8 = Methodref #4.#7 // java/lang/Object."<init>":()V
#9 = Utf8 this
#10 = Utf8 Lcom/kotlin/test11/MyClass2;
#11 = Utf8 <clinit>
#12 = Utf8 Companion
#13 = Utf8 Lcom/kotlin/test11/MyClass2$Companion;
#14 = Utf8 Lkotlin/Metadata;
#15 = Utf8 mv
#16 = Integer 1
#17 = Integer 15
#18 = Utf8 bv
#19 = Integer 0
#20 = Integer 3
#21 = Utf8 k
#22 = Utf8 d1
#23 = Utf8
\n\n\ 20:B¢¨
#24 = Utf8 d2
#25 = Utf8
#26 = Utf8 kotlin_lecture
#27 = Utf8 com/kotlin/test11/MyClass2$Companion
#28 = Class #27 // com/kotlin/test11/MyClass2$Companion
#29 = Utf8 (Lkotlin/jvm/internal/DefaultConstructorMarker;)V
#30 = NameAndType #5:#29 // "<init>":(Lkotlin/jvm/internal/DefaultConstructorMarker;)V
#31 = Methodref #28.#30 // com/kotlin/test11/MyClass2$Companion."<init>":(Lkotlin/jvm/internal/DefaultConstructorMarker;)V
#32 = NameAndType #12:#13 // Companion:Lcom/kotlin/test11/MyClass2$Companion;
#33 = Fieldref #2.#32 // com/kotlin/test11/MyClass2.Companion:Lcom/kotlin/test11/MyClass2$Companion;
#34 = Utf8 HelloKotlin7.kt
#35 = Utf8 Code
#36 = Utf8 LineNumberTable
#37 = Utf8 LocalVariableTable
#38 = Utf8 InnerClasses
#39 = Utf8 SourceFile
#40 = Utf8 RuntimeVisibleAnnotations
{
public static final com.kotlin.test11.MyClass2$Companion Companion;
descriptor: Lcom/kotlin/test11/MyClass2$Companion;
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL public com.kotlin.test11.MyClass2();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #8 // Method java/lang/Object."<init>":()V
4: return
LineNumberTable:
line 3: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this Lcom/kotlin/test11/MyClass2; static {};
descriptor: ()V
flags: ACC_STATIC
Code:
stack=3, locals=0, args_size=0
0: new #28 // class com/kotlin/test11/MyClass2$Companion
3: dup
4: aconst_null
5: invokespecial #31 // Method com/kotlin/test11/MyClass2$Companion."<init>":(Lkotlin/jvm/internal/DefaultConstructorMarker;)V
8: putstatic #33 // Field Companion:Lcom/kotlin/test11/MyClass2$Companion;
11: return
}
InnerClasses:
public static final #12= #28 of #2; //Companion=class com/kotlin/test11/MyClass2$Companion of class com/kotlin/test11/MyClass2
SourceFile: "HelloKotlin7.kt"
RuntimeVisibleAnnotations:
0: #14(#15=[I#16,I#16,I#17],#18=[I#16,I#19,I#20],#21=I#16,#22=[s#23],#24=[s#10,s#25,s#6,s#12,s#26])
木有乱码了,好,面目就可以揭开了,首先:
所以我们就可以这样来调用:
其实我们可以改变其伴身对象方法的默认规则,就得用下面这个注解了。
@JvmStatic:
在Kotlin中,我们可以将具名对象或是伴生对象中定义的函数注解为@JvmStatic,这样编译器既会在相应对象的类中生成静态方法,也会在对象自身中生成实例方法。下面来尝试一下:
此时咱们的调用方式就可以这样写了:
很明显,这个test2肯定是一个静态方法了,再来反编译看一下:
bogon:kotlin_lecture xiongwei$ javap -verbose com/kotlin/test11/MyClass2.class
Classfile /Users/xiongwei/Documents/workspace/IntelliJSpace/kotlin_lecture/out/production/kotlin_lecture/com/kotlin/test11/MyClass2.class
Last modified 2019-9-21; size 858 bytes
MD5 checksum 7b8819a8b4e7417db633e619b794273f
Compiled from "HelloKotlin7.kt"
public final class com.kotlin.test11.MyClass2
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_FINAL, ACC_SUPER
Constant pool:
#1 = Utf8 com/kotlin/test11/MyClass2
#2 = Class #1 // com/kotlin/test11/MyClass2
#3 = Utf8 java/lang/Object
#4 = Class #3 // java/lang/Object
#5 = Utf8 <init>
#6 = Utf8 ()V
#7 = NameAndType #5:#6 // "<init>":()V
#8 = Methodref #4.#7 // java/lang/Object."<init>":()V
#9 = Utf8 this
#10 = Utf8 Lcom/kotlin/test11/MyClass2;
#11 = Utf8 <clinit>
#12 = Utf8 Companion
#13 = Utf8 Lcom/kotlin/test11/MyClass2$Companion;
#14 = Utf8 Lkotlin/Metadata;
#15 = Utf8 mv
#16 = Integer 1
#17 = Integer 15
#18 = Utf8 bv
#19 = Integer 0
#20 = Integer 3
#21 = Utf8 k
#22 = Utf8 d1
#23 = Utf8
\n\n\ 20:B¢¨
#24 = Utf8 d2
#25 = Utf8
#26 = Utf8 kotlin_lecture
#27 = Utf8 test2
#28 = Utf8 Lkotlin/jvm/JvmStatic;
#29 = NameAndType #12:#13 // Companion:Lcom/kotlin/test11/MyClass2$Companion;
#30 = Fieldref #2.#29 // com/kotlin/test11/MyClass2.Companion:Lcom/kotlin/test11/MyClass2$Companion;
#31 = Utf8 com/kotlin/test11/MyClass2$Companion
#32 = Class #31 // com/kotlin/test11/MyClass2$Companion
#33 = NameAndType #27:#6 // test2:()V
#34 = Methodref #32.#33 // com/kotlin/test11/MyClass2$Companion.test2:()V
#35 = Utf8 (Lkotlin/jvm/internal/DefaultConstructorMarker;)V
#36 = NameAndType #5:#35 // "<init>":(Lkotlin/jvm/internal/DefaultConstructorMarker;)V
#37 = Methodref #32.#36 // com/kotlin/test11/MyClass2$Companion."<init>":(Lkotlin/jvm/internal/DefaultConstructorMarker;)V
#38 = Utf8 HelloKotlin7.kt
#39 = Utf8 Code
#40 = Utf8 LineNumberTable
#41 = Utf8 LocalVariableTable
#42 = Utf8 RuntimeVisibleAnnotations
#43 = Utf8 InnerClasses
#44 = Utf8 SourceFile
{
public static final com.kotlin.test11.MyClass2$Companion Companion;
descriptor: Lcom/kotlin/test11/MyClass2$Companion;
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL public com.kotlin.test11.MyClass2();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #8 // Method java/lang/Object."<init>":()V
4: return
LineNumberTable:
line 3: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this Lcom/kotlin/test11/MyClass2; static {};
descriptor: ()V
flags: ACC_STATIC
Code:
stack=3, locals=0, args_size=0
0: new #32 // class com/kotlin/test11/MyClass2$Companion
3: dup
4: aconst_null
5: invokespecial #37 // Method com/kotlin/test11/MyClass2$Companion."<init>":(Lkotlin/jvm/internal/DefaultConstructorMarker;)V
8: putstatic #30 // Field Companion:Lcom/kotlin/test11/MyClass2$Companion;
11: return public static final void test2();
descriptor: ()V
flags: ACC_PUBLIC, ACC_STATIC, ACC_FINAL
Code:
stack=1, locals=0, args_size=0
0: getstatic #30 // Field Companion:Lcom/kotlin/test11/MyClass2$Companion;
3: invokevirtual #34 // Method com/kotlin/test11/MyClass2$Companion.test2:()V
6: return
RuntimeVisibleAnnotations:
0: #28()
}
InnerClasses:
public static final #12= #32 of #2; //Companion=class com/kotlin/test11/MyClass2$Companion of class com/kotlin/test11/MyClass2
SourceFile: "HelloKotlin7.kt"
RuntimeVisibleAnnotations:
0: #14(#15=[I#16,I#16,I#17],#18=[I#16,I#19,I#20],#21=I#16,#22=[s#23],#24=[s#10,s#25,s#6,s#12,s#26])
此时确实在MyClass2字节码中生成了一个静态的test2()方法了,而它的实现很明显可以看到,它最终是调用了Companion.test2(),其根本就是由该@JvmStatic注解发生了作用。
最新文章
- vue2.0---模板语法
- 猜拳游戏GuessGame源码
- 【codevs1993】 草地排水
- Jetty多Connector
- Solve: Your project references the latest version of Entity Framework (for MySQL) in Visual Studio 2013
- Sqlserver_In、exists使用
- Linux下SVN服务器安装配置及客户端安装说明
- Python访问私有变量
- poj 2983 差分约束
- 352. Data Stream as Disjoint Intervals
- aix光盘安装包 aix puppet agent 自动化安装
- 应用 Valgrind 发现 Linux 程序的内存问题
- 前端开发规范:命名规范、html 规范、css 规范、js 规范
- [转]Nginx基本功能极速入门
- NetStateReceiver【监听网路状态变化】
- Ocelot简易教程(四)之请求聚合以及服务发现
- 50个常用的Linux命令(三)awk
- Matlab forward Euler demo
- LOJ #2802. 「CCC 2018」平衡树(整除分块 + dp)
- 前端解读控制反转(IOC)