Mastering Java Bytecode - JAX.de 2012
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The document discusses bytecode and the Java Virtual Machine (JVM). It provides an example of decompiling the "Hello World" Java program using javap to view the bytecode instructions. It also covers bytecode fundamentals like the stack machine model, instruction types, and how the operand stack and frames work. Finally, it demonstrates some common stack manipulation instructions.
![C:workgeeconclasses>javap Hello -c
Compiled from "Hello.java"
public class Hello extends java.lang.Object{
public Hello();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #3; //String Hello, World!
5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V](https://image.slidesharecdn.com/jax-masteringjavabytecode-120418182312-phpapp02/85/Mastering-Java-Bytecode-JAX-de-2012-37-320.jpg)
![C:workgeeconclasses>javap Hello -c
Compiled from "Hello.java"
public class Hello extends java.lang.Object{
public Hello();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
get static field
public static void main(java.lang.String[]);
Code:
0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #3; //String Hello, World!
5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V](https://image.slidesharecdn.com/jax-masteringjavabytecode-120418182312-phpapp02/85/Mastering-Java-Bytecode-JAX-de-2012-38-320.jpg)
![C:workgeeconclasses>javap Hello -c
Compiled from "Hello.java"
public class Hello extends java.lang.Object{
public Hello();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #3; //String Hello, World!
5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
load string to the stack](https://image.slidesharecdn.com/jax-masteringjavabytecode-120418182312-phpapp02/85/Mastering-Java-Bytecode-JAX-de-2012-39-320.jpg)
![C:workgeeconclasses>javap Hello -c
Compiled from "Hello.java"
public class Hello extends java.lang.Object{
public Hello();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #3; //String Hello, World!
5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
invoke method with parameter](https://image.slidesharecdn.com/jax-masteringjavabytecode-120418182312-phpapp02/85/Mastering-Java-Bytecode-JAX-de-2012-40-320.jpg)
![C:workgeeconclasses>javap Hello -c
Compiled from "Hello.java"
public class Hello extends java.lang.Object{
public Hello();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #3; //String Hello, World!
5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V](https://image.slidesharecdn.com/jax-masteringjavabytecode-120418182312-phpapp02/85/Mastering-Java-Bytecode-JAX-de-2012-41-320.jpg)
![What’s #1,#2, etc ?
C:workgeeconclasses>javap Hello -c
Compiled from "Hello.java"
public class Hello extends java.lang.Object{
public Hello();
Code:
0: aload_0
1: invokespecial #1; //Method java/lang/Object."<init>":()V
4: return
public static void main(java.lang.String[]);
Code:
0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #3; //String Hello, World!
5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V](https://image.slidesharecdn.com/jax-masteringjavabytecode-120418182312-phpapp02/85/Mastering-Java-Bytecode-JAX-de-2012-42-320.jpg)
![C:workgeeconclasses>javap Hello -c -verbose
…
public static void main(java.lang.String[]);
Code:
Stack=2, Locals=1, Args_size=1
0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream;
3: ldc #3; //String Hello, World!
5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
8: return
LineNumberTable:
line 4: 0
line 5: 8
LocalVariableTable:
Start Length Slot Name Signature
0 9 0 args [Ljava/lang/String;](https://image.slidesharecdn.com/jax-masteringjavabytecode-120418182312-phpapp02/85/Mastering-Java-Bytecode-JAX-de-2012-50-320.jpg)
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Mastering Java Bytecode - JAX.de 2012
- 1. Mastering Java Bytecode Anton Arhipov | ZeroTurnaround
- 2. whoami • Anton Arhipov • Java Dev / Product Lead • ZeroTurnaround, JRebel • @antonarhipov @javarebel
- 3. Today – Java Core • Mastering Java Bytecode • The Future of Java on Multi- Core, Lambdas, Spliterators and Methods • OpenJDK JVM Internals • Invokedynamic Deep Dive
- 5. Why Bytecode? • Know your platform! • Create your own compiler? • Programming model (AOP, ORM) • Awesome tools (JRebel ) • … just bored?
- 6. THE INTRO
- 7. 1+2
- 8. 1+2 12+
- 9. 1+2 12+
- 10. 1+2 12+ PUSH 1 1
- 11. 1+2 12+ PUSH 1 PUSH 2 2 1
- 12. 1+2 12+ PUSH 1 PUSH 2 3 ADD
- 13. 1+2 12+ ICONST_1 ICONST_2 3 IADD
- 14. ?=1+2
- 15. TAXONOMY
- 16. Bytecode • One-byte instructions • 256 possible opcodes • 200+ in use
- 17. TYPE OPERATION
- 18. TYPE OPERATION • <TYPE> ::= b, s, c, i, l, f, d, a
- 19. TYPE OPERATION • <TYPE> ::= b, s, c, i, l, f, d, a • constant values (ldc, iconst_1)
- 20. TYPE OPERATION • <TYPE> ::= b, s, c, i, l, f, d, a • constant values (ldc, iconst_1) • Local variables and stack interaction (load/store) • Array operations (aload, astore) • Math (add, sub, mul, div) • Boolean/bitwise operations (iand, ixor) • Comparisons (cmpg, cmpl, ifne, ifeq) • Conversions (l2d, i2l)
- 22. Bytecode Taxonomy Stack Manipulation
- 23. Bytecode Taxonomy Stack Flow Manipulation Control
- 24. Bytecode Taxonomy Stack Flow Manipulation Control Object Model
- 25. Bytecode Taxonomy Stack Flow Manipulation Control Object Arithmetics Model
- 26. Bytecode Taxonomy Stack Flow Manipulation Control monitorenter monitorexit Object Arithmetics Model
- 27. TOOLING
- 28. javap • Java class file disassembler • Used with no options shows class structure only – Methods, superclass, interfaces, etc • -c shows the bytecode • -private shows all methods and members • -s prints internal signatures • -l prints line numbers and local variable tables
- 29. HELLO WORLD!
- 31. C:workgeeconclasses>javap Hello -c
- 32. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return
- 33. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: the default constructor 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return
- 34. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: push this to stack 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return
- 35. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return invoke <init> on this
- 36. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return
- 37. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
- 38. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return get static field public static void main(java.lang.String[]); Code: 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
- 39. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V load string to the stack
- 40. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V invoke method with parameter
- 41. C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
- 42. What’s #1,#2, etc ? C:workgeeconclasses>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
- 43. C:workgeeconclasses>javap Hello -c -verbose
- 44. C:workgeeconclasses>javap Hello -c -verbose
- 45. C:workgeeconclasses>javap Hello -c -verbose Compiled from "Hello.java“ public class Hello extends java.lang.Object SourceFile: "Hello.java" minor version: 0 major version: 50 Constant pool: const #1 = Method #6.#20; // java/lang/Object."<init>":()V const #2 = Field #21.#22; // java/lang/System.out:Ljava/io/PrintStream; const #3 = String #23; // Hello, World! const #4 = Method #24.#25; // java/io/PrintStream.println:(Ljava/lang/String;)V const #5 = class #26; // Hello const #6 = class #27; // java/lang/Object const #7 = Asciz <init>; const #8 = Asciz ()V;
- 46. C:workgeeconclasses>javap Hello -c -verbose Compiled from "Hello.java“ public class Hello extends java.lang.Object SourceFile: "Hello.java" minor version: 0 major version: 50 Constant pool: const #1 = Method #6.#20; // java/lang/Object."<init>":()V const #2 = Field #21.#22; // java/lang/System.out:Ljava/io/PrintStream; const #3 = String #23; // Hello, World! const #4 = Method #24.#25; // java/io/PrintStream.println:(Ljava/lang/String;)V const #5 = class #26; // Hello const #6 = class #27; // java/lang/Object const #7 = Asciz <init>; const #8 = Asciz ()V;
- 47. C:workgeeconclasses>javap Hello -c -verbose … public Hello(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return LineNumberTable: line 1: 0 LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LHello;
- 48. C:workgeeconclasses>javap Hello -c -verbose … public Hello(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return LineNumberTable: line 1: 0 LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LHello;
- 49. C:workgeeconclasses>javap Hello -c -verbose … public Hello(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return LineNumberTable: line 1: 0 LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LHello;
- 50. C:workgeeconclasses>javap Hello -c -verbose … public static void main(java.lang.String[]); Code: Stack=2, Locals=1, Args_size=1 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V 8: return LineNumberTable: line 4: 0 line 5: 8 LocalVariableTable: Start Length Slot Name Signature 0 9 0 args [Ljava/lang/String;
- 52. Stack Machine
- 53. Stack Machine • JVM is a stack-based machine
- 54. Stack Machine • JVM is a stack-based machine • Each thread has a stack
- 55. Stack Machine • JVM is a stack-based machine • Each thread has a stack • Stack stores frames
- 56. Stack Machine • JVM is a stack-based machine • Each thread has a stack • Stack stores frames • Frame is created on method invocation
- 57. Stack Machine • JVM is a stack-based machine • Each thread has a stack • Stack stores frames • Frame is created on method invocation • Frame consists of: – Operand stack – Array of local variables
- 58. The Frame Local variables 0 1 2 … N Operand stack #1 Constant Pool
- 59. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
- 60. 0 1 2 3 4 aload_0 getfield 00 02 areturn public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
- 61. 0 1 2 3 4 2A B4 00 02 B0 public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
- 62. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
- 63. STACK CRUNCHING
- 64. dup A pop B swap dup_x1 dup2_x1
- 65. dup A pop A swap B dup_x1 dup2_x1
- 66. dup A pop B swap dup_x1 dup2_x1
- 67. dup B pop A swap dup_x1 dup2_x1
- 68. dup B pop A swap B dup_x1 dup2_x1
- 69. dup B pop A swap B dup_x1 B dup2_x1 A
- 70. dup2_x2 How do you swap doubles?
- 71. dup2_x2
- 72. dup2_x2 dconst_0 0.0
- 73. dup2_x2 dconst_0 dconst_1 1.0 0.0
- 74. dup2_x2 dconst_0 dconst_1 1.0 swap 0.0
- 75. dup2_x2 dconst_0 dconst_1 1.0 swap not allowed! 0.0
- 76. dup2_x2 dconst_0 dconst_1 1.0 swap2 0.0
- 77. dup2_x2 dconst_0 dconst_1 1.0 doesn’t swap2 exist 0.0
- 78. dup2_x2 dconst_0 dconst_1 1.0 dup2_x2 0.0 1.0
- 79. dup2_x2 dconst_0 dconst_1 0.0 dup2_x2 pop2 1.0
- 80. dup2_x2 dconst_0 dconst_1 0.0 dup2_x2 pop2 1.0 profit!
- 81. LOCAL VARIABLES
- 82. Local Variables
- 83. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
- 84. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
- 85. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
- 86. Local Variables The table public int calculate(int); Code: maps Stack=2, Locals=2, Args_size=2 numbers to … names LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
- 87. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 Sized explicitly … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
- 88. Local Variables Stack var value depth value ldc "Hello" 0 0 astore_0 1 iconst_1 1 astore_1 2 aload_0 2 3 3 4 4
- 89. Local Variables Stack var value depth value ldc "Hello" 0 0 "Hello" astore_0 1 iconst_1 1 astore_1 2 aload_0 2 3 3 4 4
- 90. Local Variables Stack var value depth value ldc "Hello" 0 "Hello" 0 astore_0 1 iconst_1 1 astore_1 2 aload_0 2 3 3 4 4
- 91. Local Variables Stack var value depth value ldc "Hello" 0 "Hello" 0 1 astore_0 1 iconst_1 1 astore_1 2 aload_0 2 3 3 4 4
- 92. Local Variables Stack var value depth value ldc "Hello" 0 "Hello" 0 astore_0 1 1 iconst_1 1 astore_1 2 aload_0 2 3 3 4 4
- 93. Local Variables Stack var value depth value ldc "Hello" 0 "Hello" 0 "Hello" astore_0 1 1 iconst_1 1 astore_1 2 aload_0 2 3 3 4 4
- 94. load Local Variables Stack Table store
- 95. OBJECTS
- 96. Object Initialization new 0xBB <init> Instance initialization method <clinit> Class and interface initialization method
- 97. Object Initialization: static {} static {}; Code: 0: iconst_1 1: putstatic #2; //Field a:I 4: iconst_2 5: putstatic #3; //Field b:I 8: return
- 98. Object Initialization: static {} <clinit> static {}; Code: 0: iconst_1 1: putstatic #2; //Field a:I 4: iconst_2 5: putstatic #3; //Field b:I 8: return
- 101. Object Initialization: new public Initializer(); Code:
- 102. Object Initialization: new public Initializer(); Code: 0: aload_0
- 103. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V
- 104. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: aload_0
- 105. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: aload_0 5: new #2; //class java/lang/Object 8: dup
- 106. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: aload_0 5: new #2; //class java/lang/Object 8: dup 9: invokespecial #1; //Method java/lang/Object."<init>":()V 12: putfield #3; //Field o:Ljava/lang/Object;
- 107. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: aload_0 5: new #2; //class java/lang/Object 8: dup 9: invokespecial #1; //Method java/lang/Object."<init>":()V 12: putfield #3; //Field o:Ljava/lang/Object; 15: return
- 108. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: aload_0 5: new #2; //class java/lang/Object 8: dup 9: invokespecial #1; //Method java/lang/Object."<init>":()V 12: putfield #3; //Field o:Ljava/lang/Object; 15: return
- 111. Object Initialization: {} public Initializer(int); Code: 0:aload_0 1:invokespecial #1; // ..<init> 4:aload_0 5:iconst_1 6:putfield #2; //Field a:I 9:aload_0 10:iconst_2 11: putfield #3; //Field c:I 14:aload_0 15:iload_1 16:putfield #4; //Field b:I 19:return
- 114. METHOD INVOCATION
- 115. invokeXXX • invokestatic • invokespecial • invokevirtual • invokeinterface • invokedynamic
- 116. invokestatic • invokestatic • invokespecial • invokevirtual Integer.valueOf(“42”) • invokeinterface • invokedynamic
- 117. invokespecial • invokestatic <init> • invokespecial • invokevirtual private void foo(); • invokeinterface • invokedynamic super.method();
- 118. invokevirtual class A • invokestatic A/method1 A/method2 • invokespecial • invokevirtual • invokeinterface • invokedynamic
- 119. invokevirtual class A • invokestatic A/method1 A/method2 • invokespecial class B • invokevirtual • invokeinterface • invokedynamic
- 120. invokevirtual class A • invokestatic A/method1 A/method2 • invokespecial class B • invokevirtual A/method1 B/method2 • invokeinterface B/method3 • invokedynamic
- 121. invokeinterface class A • invokestatic A/method1 A/method2 • invokespecial class B impl X • invokevirtual A/method1 B/method2 • invokeinterface B/method3 X/methodX • invokedynamic
- 122. invokeinterface class A • invokestatic A/method1 A/method2 • invokespecial class B impl X • invokevirtual A/method1 • invokeinterface B/method2 B/method3 D impl X X/methodX D/method1 • invokedynamic X/methodX
- 123. invokeinterface class A • invokestatic A/method1 A/method2 • invokespecial class B impl X • invokevirtual A/method1 • invokeinterface B/method2 B/method3 D impl X X/methodX D/method1 • invokedynamic X/methodX
- 124. invokeinterface class A • invokestatic A/method1 A/method2 • invokespecial class B impl X • invokevirtual A/method1 • invokeinterface B/method2 B/method3 D impl X X/methodX D/method1 • invokedynamic X/methodX Efficient Implementation of Java Interfaces: Invokeinterface Considered Harmless, Bowen Alpern, Anthony Cocchi, Stephen Fink, David Grove, and Derek Lieber, OOPSLA’01
- 125. Method Invocation
- 128. Method Invocation obj.method(param1, param2); push obj push param1 push param2 call method
- 129. Method Invocation obj.method(param1, param2); obj push obj push param1 push param2 call method
- 130. Method Invocation obj.method(param1, param2); param1 push obj obj push param1 push param2 call method
- 131. Method Invocation obj.method(param1, param2); param2 push obj param1 push param1 push param2 obj call method
- 132. Method Invocation obj.method(param1, param2); obj? push obj push param1 push param2 call method
- 133. Method Invocation this.add(1, 2); 0: aload_0 1: iconst_1 2: iconst_2 3: invokevirtual #2; //Method add:(II)I
- 134. INNER CLASSES
- 135. Inner Classes
- 136. Inner Classes
- 137. Inner Classes class Car$Engine extends j.l.Object{ final Car this$0; Car$Engine(Car); public void start(); Code: 0: aload_0 1: getfield #1; //Field this$0:LCar; 4: invokestatic #3; // Car.access$000:(LCar;)V 7: return }
- 138. Inner Classes public class Car extends j.l.Object{ public Car(); private void move(); class Car$Engine extends j.l.Object{ final Car this$0; static void access$000(Car); Code: Car$Engine(Car); 0: aload_0 1: invokespecial #1; // move: ()V; public void start(); 4: return Code: } 0: aload_0 1: getfield #1; //Field this$0:LCar; 4: invokestatic #3; // Car.access$000:(LCar;)V 7: return }
- 139. Inner Classes public class Car extends j.l.Object{ public Car(); private void move(); class Car$Engine extends j.l.Object{ final Car this$0; static void access$000(Car); Code: Car$Engine(Car); 0: aload_0 1: invokespecial #1; // move: ()V; public void start(); 4: return Code: } 0: aload_0 1: getfield #1; //Field this$0:LCar; 4: invokestatic #3; // Car.access$000:(LCar;)V 7: return }
- 140. “HOW DO THEY DO THAT?”
- 141. object Singleton { def test={} }
- 142. object Singleton { def test={} } $> scalac Singleton.scala Singleton.class Singleton$.class
- 143. public final class Singleton extends java.lang.Object { public static final void test(); Code: 0: getstatic #11; //Field Singleton$.MODULE$:LSingleton$; 3: invokevirtual #13; //Method Singleton$.test:()V 6: return }
- 144. public final class Singleton extends java.lang.Object { public static final void test(); Code: 0: getstatic #11; //Field Singleton$.MODULE$:LSingleton$; 3: invokevirtual #13; //Method Singleton$.test:()V 6: return }
- 145. public final class Singleton extends java.lang.Object { public static final void test(); Code: 0: getstatic #11; //Field Singleton$.MODULE$:LSingleton$; 3: invokevirtual #13; //Method Singleton$.test:()V 6: return }
- 146. public final class Singleton extends java.lang.Object { public static final void test(); Code: 0: getstatic #11; //Field Singleton$.MODULE$:LSingleton$; 3: invokevirtual #13; //Method Singleton$.test:()V 6: return } public final class Singleton$ extends java.lang.Object implements scala.ScalaObject { public static final Singleton$ MODULE$; public static {}; Code: 0: new #9; //class Singleton$ 3: invokespecial #12; //Method "<init>":()V 6: return public void test(); private Singleton$(); }
- 147. public final class Singleton extends java.lang.Object { public static final void test(); Code: 0: getstatic #11; //Field Singleton$.MODULE$:LSingleton$; 3: invokevirtual #13; //Method Singleton$.test:()V 6: return } public final class Singleton$ extends java.lang.Object implements scala.ScalaObject { public static final Singleton$ MODULE$; public static {}; Code: 0: new #9; //class Singleton$ 3: invokespecial #12; //Method "<init>":()V 6: return public void test(); private Singleton$(); }
- 148. public final class Singleton extends java.lang.Object { public static final void test(); Code: 0: getstatic #11; //Field Singleton$.MODULE$:LSingleton$; 3: invokevirtual #13; //Method Singleton$.test:()V 6: return } public final class Singleton$ extends java.lang.Object implements scala.ScalaObject { public static final Singleton$ MODULE$; public static {}; Code: 0: new #9; //class Singleton$ 3: invokespecial #12; //Method "<init>":()V 6: return public void test(); private Singleton$(); }
- 149. public final class Singleton extends java.lang.Object { public static final void test(); Code: 0: getstatic #11; //Field Singleton$.MODULE$:LSingleton$; 3: invokevirtual #13; //Method Singleton$.test:()V 6: return } public final class Singleton$ extends java.lang.Object implements scala.ScalaObject { public static final Singleton$ MODULE$; public static {}; public void test(); private Singleton$(); Code: 0: aload_0 1: invokespecial #17; //Method java/lang/Object."<init>":()V 4: aload_0 5: putstatic #19; //Field MODULE$:LSingleton$; 8: return
- 150. object Singleton { def test={} }
- 151. public class Singleton { public void test(){ Singleton$.MODULE$.test(); } } object Singleton { def test={} }
- 152. public class Singleton { public void test(){ Singleton$.MODULE$.test(); } } public final class Singleton$ object Singleton { implements scala.ScalaObject { def test={} public static final Singleton$ MODULE$; } static { new Singleton$(); } private Singleton$(){ MODULE$ = this; } public void test() { } }
- 153. class Groovy { }
- 154. class Groovy { } $> groovyc Groovy.groovy $> javap –c –p Groovy
- 155. class Groovy { } $> groovyc Groovy.groovy $> javap –c –p Groovy public class Test extends java.lang.Object implements groovy.lang.GroovyObject{ private static org.codehaus.groovy.reflection.ClassInfo $staticClassInfo; private transient groovy.lang.MetaClass metaClass; public static java.lang.Long __timeStamp; public static java.lang.Long __timeStamp__239_neverHappen1304807931117; private static java.lang.ref.SoftReference $callSiteArray; private static java.lang.Class $class$groovy$lang$MetaClass; private static java.lang.Class $class$Test; private static java.lang.Class $class$java$lang$String; public java.lang.Object this$dist$invoke$2(java.lang.String, java.lang.Object); public void this$dist$set$2(java.lang.String, java.lang.Object); public java.lang.Object this$dist$get$2(java.lang.String); protected groovy.lang.MetaClass $getStaticMetaClass(); public groovy.lang.MetaClass getMetaClass(); public void setMetaClass(groovy.lang.MetaClass); public java.lang.Object invokeMethod(java.lang.String, java.lang.Object); public java.lang.Object getProperty(java.lang.String); public void setProperty(java.lang.String, java.lang.Object);
- 156. OBJECTWEB ASM