in practice source code source code javac scalac groovyc jrubyc - - PowerPoint PPT Presentation

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in practice source code source code javac scalac groovyc jrubyc - - PowerPoint PPT Presentation

Mar 19, 2024 93 likes •1.6k views

Java byte code in practice source code source code javac scalac groovyc jrubyc 0xCAFEBABE byte code source code javac scalac groovyc jrubyc 0xCAFEBABE byte code class loader interpreter JIT compiler JVM source code javac

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Java byte code in practice

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source code

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0xCAFEBABE source code byte code javac scalac groovyc jrubyc

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0xCAFEBABE source code byte code JVM javac scalac groovyc jrubyc JIT compiler interpreter class loader

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0xCAFEBABE source code byte code JVM javac scalac groovyc jrubyc JIT compiler interpreter class loader creates

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0xCAFEBABE source code byte code JVM javac scalac groovyc jrubyc JIT compiler interpreter class loader creates reads

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0xCAFEBABE source code byte code JVM javac scalac groovyc jrubyc JIT compiler interpreter class loader creates reads runs

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source code byte code void foo() { }

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source code byte code void foo() { } RETURN

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source code byte code void foo() { } RETURN return;

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source code byte code void foo() { } return; 0xB1

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source code byte code int foo() { return 1 + 2; }

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source code byte code int foo() { return 1 + 2; } ICONST_1 ICONST_2 IADD

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source code byte code int foo() { return 1 + 2; } ICONST_1 ICONST_2 IADD

  • perand stack
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source code byte code int foo() { return 1 + 2; } ICONST_1 ICONST_2 IADD

  • perand stack

1

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source code byte code int foo() { return 1 + 2; } ICONST_1 ICONST_2 IADD

  • perand stack

2 1

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source code byte code int foo() { return 1 + 2; } ICONST_1 ICONST_2 IADD

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3

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source code byte code int foo() { return 1 + 2; } ICONST_1 ICONST_2 IADD

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3 IRETURN

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source code byte code int foo() { return 1 + 2; } ICONST_1 ICONST_2 IADD

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IRETURN

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source code byte code int foo() { return 1 + 2; }

  • perand stack

0x04 0x05 0x60 0xAC

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source code byte code int foo() { return 11 + 2; }

  • perand stack
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source code byte code BIPUSH int foo() { return 11 + 2; }

  • perand stack

11

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source code byte code BIPUSH int foo() { return 11 + 2; }

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11 11

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source code byte code ICONST_2 IADD IRETURN BIPUSH int foo() { return 11 + 2; }

  • perand stack

11 11

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source code byte code ICONST_2 IADD IRETURN BIPUSH int foo() { return 11 + 2; }

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2 11 11

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source code byte code ICONST_2 IADD IRETURN BIPUSH int foo() { return 11 + 2; }

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13 11

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source code byte code ICONST_2 IADD IRETURN BIPUSH int foo() { return 11 + 2; }

  • perand stack

11

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source code byte code ICONST_2 IADD IRETURN int foo() { return 11 + 2; }

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0x10 11

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source code byte code ICONST_2 IADD IRETURN int foo() { return 11 + 2; }

  • perand stack

0x10 0x0B

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source code byte code int foo() { return 11 + 2; }

  • perand stack

0x05 0x60 0xAC 0x10 0x0B

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source code byte code int foo(int i) { return i + 1; }

  • perand stack
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source code byte code int foo(int i) { return i + 1; } ILOAD_1

  • perand stack
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source code byte code int foo(int i) { return i + 1; } ILOAD_1

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local variable array 1 : i 0 : this

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source code byte code int foo(int i) { return i + 1; } ILOAD_1

  • perand stack

local variable array 1 : i 0 : this i

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source code byte code int foo(int i) { return i + 1; } ILOAD_1 ICONST_1 IADD IRETURN

  • perand stack

local variable array 1 : i 0 : this i

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source code byte code int foo(int i) { return i + 1; } ILOAD_1 ICONST_1 IADD IRETURN

  • perand stack

local variable array 1 : i 0 : this 1 i

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source code byte code int foo(int i) { return i + 1; } ILOAD_1 ICONST_1 IADD IRETURN

  • perand stack

local variable array 1 : i 0 : this i + 1

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source code byte code int foo(int i) { return i + 1; } ILOAD_1 ICONST_1 IADD IRETURN

  • perand stack

local variable array 1 : i 0 : this

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source code byte code int foo(int i) { return i + 1; }

  • perand stack

local variable array 1 : i 0 : this 0x1B 0x04 0x60 0xAC

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source code byte code long foo(long i) { return i + 1L; }

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source code byte code long foo(long i) { return i + 1L; } LLOAD_1 LCONST_1 LADD LRETURN

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source code byte code long foo(long i) { return i + 1L; } LLOAD_1 LCONST_1 LADD LRETURN local variable array 2 : i (cn.) 1 : i 0 : this

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source code byte code long foo(long i) { return i + 1L; } LLOAD_1 LCONST_1 LADD LRETURN

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local variable array 2 : i (cn.) 1 : i 0 : this i (cn.) i

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source code byte code long foo(long i) { return i + 1L; } LLOAD_1 LCONST_1 LADD LRETURN

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local variable array 2 : i (cn.) 1 : i 0 : this i (cn.) i 1L 1L (cn.)

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source code byte code long foo(long i) { return i + 1L; } LLOAD_1 LCONST_1 LADD LRETURN

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local variable array 2 : i (cn.) 1 : i 0 : this i + 1L i + 1L (cn.)

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source code byte code long foo(long i) { return i + 1L; } LLOAD_1 LCONST_1 LADD LRETURN

  • perand stack

local variable array 2 : i (cn.) 1 : i 0 : this

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source code byte code long foo(long i) { return i + 1L; }

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local variable array 2 : i (cn.) 1 : i 0 : this 0x1F 0x0A 0x61 0xAD

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source code byte code short foo(short i) { return (short) (i + 1); }

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local variable array 1 : i 0 : this

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD

  • perand stack

local variable array 1 : i 0 : this

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD

  • perand stack

local variable array 1 : i 0 : this i

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD

  • perand stack

local variable array 1 : i 0 : this 1 i

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD

  • perand stack

local variable array 1 : i 0 : this i + 1

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD I2S

  • perand stack

local variable array 1 : i 0 : this i + 1

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD I2S

  • perand stack

local variable array 1 : i 0 : this i + 1

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD I2S IRETURN

  • perand stack

local variable array 1 : i 0 : this i + 1

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source code byte code short foo(short i) { return (short) (i + 1); } ILOAD_1 ICONST_1 IADD I2S IRETURN

  • perand stack

local variable array 1 : i 0 : this

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source code byte code short foo(short i) { return (short) (i + 1); }

  • perand stack

local variable array 1 : i 0 : this 0x1B 0x04 0x60 0x93 0xAC

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source code byte code void foo() { return; } RETURN

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source code byte code void foo() { return; } RETURN

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source code byte code void foo() { return; } RETURN

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source code byte code void foo() { return; } RETURN 0x0000 foo ()V

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source code byte code void foo() { return; } RETURN 0x0000 foo ()V 1

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///////////////// local variable array 0 : this

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source code byte code void foo() { return; } RETURN 0x0000 foo ()V 1

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///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } RETURN package pkg; class Bar { } 0x0000 foo ()V 1

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///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } RETURN package pkg; class Bar { } constant pool (i.a. UTF-8) 0x0000 foo ()V 1

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///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } RETURN package pkg; class Bar { } constant pool (i.a. UTF-8) 0x0000: foo 0x0001: ()V 0x0002: pkg/Bar 0x0000 foo ()V 1

  • perand stack

///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } RETURN package pkg; class Bar { } constant pool (i.a. UTF-8) 0x0000: foo 0x0001: ()V 0x0002: pkg/Bar 0x0000 0x0000 ()V 1

  • perand stack

///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } RETURN package pkg; class Bar { } constant pool (i.a. UTF-8) 0x0000: foo 0x0001: ()V 0x0002: pkg/Bar 0x0000 0x0000 0x0001 1

  • perand stack

///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } package pkg; class Bar { } constant pool (i.a. UTF-8) 0x0000: foo 0x0001: ()V 0x0002: pkg/Bar 0xB1 0x0000 0x0000 0x0001 1

  • perand stack

///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } package pkg; class Bar { } constant pool (i.a. UTF-8) 0x0000: foo 0x0001: ()V 0x0002: pkg/Bar 0xB1 0x0000 0x0000 0x0001 0x0000 1

  • perand stack

///////////////// local variable array 0 : this

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source code byte code pkg/Bar.class void foo() { return; } package pkg; class Bar { } constant pool (i.a. UTF-8) 0x0000: foo 0x0001: ()V 0x0002: pkg/Bar 0xB1 0x0000 0x0000 0x0001 0x0000 0x0001

  • perand stack

///////////////// local variable array 0 : this

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Java type JVM type (non-array) JVM descriptor stack slots boolean I Z 1 byte B 1 short S 1 char C 1 int I 1 long L J 2 float F F 1 double D D 2 void

  • V

java.lang.Object A Ljava/lang/Object; 1

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } }

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I local variable array 1 : i 0 : this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I local variable array 1 : i 0 : this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 local variable array 1 : i 0 : this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN local variable array 1 : i 0 : this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN

  • perand stack

local variable array 1 : i 0 : this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN

  • perand stack

local variable array 1 : i 0 : this this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN

  • perand stack

local variable array 1 : i 0 : this i this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN

  • perand stack

local variable array 1 : i 0 : this 1 this i

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN

  • perand stack

local variable array 1 : i 0 : this this i + 1

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN

  • perand stack

local variable array 1 : i 0 : this foo(i + 1)

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } ILOAD_1 ICONST_1 IADD INVOKEVIRTUAL pkg/Bar foo (I)I ALOAD_0 IRETURN

  • perand stack

local variable array 1 : i 0 : this

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } INVOKEVIRTUAL pkg/Bar foo (I)I

  • perand stack

local variable array 1 : i 0 : this 0x2A 0x1B 0x04 0x60 0xAC

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } } pkg/Bar foo (I)I

  • perand stack

local variable array 1 : i 0 : this 0x2A 0x1B 0x04 0x60 0xAC 0xB6

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source code byte code package pkg; class Bar { int foo(int i) { return foo(i + 1); } }

  • perand stack

local variable array 1 : i 0 : this 0x2A 0x1B 0x04 0x60 0xAC 0xB6 constant pool 0x0002 0x0000 0x0001

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INVOKESTATIC Invokes a static method. pkg/Bar foo ()V

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INVOKEVIRTUAL INVOKESTATIC Invokes a static method. pkg/Bar foo ()V pkg/Bar foo ()V Invokes the most-specific version of an inherited method on a non-interface class.

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INVOKESPECIAL INVOKEVIRTUAL INVOKESTATIC Invokes a static method. pkg/Bar foo ()V pkg/Bar foo ()V Invokes the most-specific version of an inherited method on a non-interface class. pkg/Bar foo ()V Invokes a super class‘s version of an inherited method. Invokes a “constructor method”. Invokes a private method. Invokes an interface default method (Java 8).

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INVOKESPECIAL INVOKEVIRTUAL INVOKESTATIC INVOKEINTERFACE Invokes a static method. pkg/Bar foo ()V pkg/Bar foo ()V Invokes the most-specific version of an inherited method on a non-interface class. pkg/Bar foo ()V Invokes a super class‘s version of an inherited method. Invokes a “constructor method”. Invokes a private method. Invokes an interface default method (Java 8). pkg/Bar foo ()V Invokes an interface method. (Similar to INVOKEVIRTUAL but without virtual method table index optimization.)

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INVOKESPECIAL INVOKEVIRTUAL INVOKESTATIC INVOKEINTERFACE INVOKEDYNAMIC Invokes a static method. pkg/Bar foo ()V pkg/Bar foo ()V Invokes the most-specific version of an inherited method on a non-interface class. pkg/Bar foo ()V Invokes a super class‘s version of an inherited method. Invokes a “constructor method”. Invokes a private method. Invokes an interface default method (Java 8). pkg/Bar foo ()V Invokes an interface method. (Similar to INVOKEVIRTUAL but without virtual method table index optimization.) foo ()V bootstrap Queries the given bootstrap method for locating a method implementation at runtime. (MethodHandle: Combines a specific method and an INVOKE* instruction.)

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INVOKESPECIAL INVOKEVIRTUAL INVOKESTATIC INVOKEINTERFACE INVOKEDYNAMIC Invokes a static method. pkg/Bar foo ()V pkg/Bar foo ()V Invokes the most-specific version of an inherited method on a non-interface class. pkg/Bar foo ()V Invokes a super class‘s version of an inherited method. Invokes a “constructor method”. Invokes a private method. Invokes an interface default method (Java 8). pkg/Bar foo ()V Invokes an interface method. (Similar to INVOKEVIRTUAL but without virtual method table index optimization.) foo ()V bootstrap Queries the given bootstrap method for locating a method implementation at runtime. (MethodHandle: Combines a specific method and an INVOKE* instruction.)

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void foo() { ???(); // invokedynamic } foo() ?

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void foo() { ???(); // invokedynamic } foo() ? bootstrap()

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void foo() { ???(); // invokedynamic } foo() ? bootstrap() bar()

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foo() ? bootstrap() bar() void foo() { bar(); }

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foo() ? bar() void foo() { bar(); }

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foo() ? qux() bar() void foo() { bar(); }

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foo() ? qux() bar() void foo() { bar(); } In theory, this could be achieved by using reflection. However, using invokedynamic

  • ffers a more native approach. This is especially important when dealing with

primitive types (double boxing). Used to implement lambda expressions, more important for dynamic languages.

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@interface Secured { String user(); } class SecurityHolder { static String user = "ANONYMOUS"; }

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class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } } @interface Secured { String user(); } class SecurityHolder { static String user = "ANONYMOUS"; }

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interface Framework { <T> Class<? extends T> secure(Class<T> type); } class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } } @interface Secured { String user(); } class SecurityHolder { static String user = "ANONYMOUS"; }

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interface Framework { <T> Class<? extends T> secure(Class<T> type); } class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } } @interface Secured { String user(); } class SecurityHolder { static String user = "ANONYMOUS"; }

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interface Framework { <T> Class<? extends T> secure(Class<T> type); } class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } } @interface Secured { String user(); } class SecurityHolder { static String user = "ANONYMOUS"; }

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interface Framework { <T> Class<? extends T> secure(Class<T> type); } class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } } @interface Secured { String user(); } class SecurityHolder { static String user = "ANONYMOUS"; } does not know about depends on

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interface Framework { <T> Class<? extends T> secure(Class<T> type); } class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } } @interface Secured { String user(); } class SecurityHolder { static String user = "ANONYMOUS"; } does not know about depends on discovers at runtime

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class Service { @Secured(user = "ADMIN") void deleteEverything() { if(!"ADMIN".equals(UserHolder.user)) { throw new IllegalStateException("Wrong user"); } // delete everything... } } redefine class (build time, agent) class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } }

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create subclass (Liskov substitution) class SecuredService extends Service { @Override void deleteEverything() { if(!"ADMIN".equals(UserHolder.user)) { throw new IllegalStateException("Wrong user"); } super.deleteEverything(); } } class Service { @Secured(user = "ADMIN") void deleteEverything() { // delete everything... } }

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The “black magic” prejudice. var service = { /* @Secured(user = "ADMIN") */ deleteEverything: function () { // delete everything ... } }

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The “black magic” prejudice. var service = { /* @Secured(user = "ADMIN") */ deleteEverything: function () { // delete everything ... } } function run(service) { service.deleteEverything(); }

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The “black magic” prejudice. var service = { /* @Secured(user = "ADMIN") */ deleteEverything: function () { // delete everything ... } } function run(service) { service.deleteEverything(); } No type, no problem. (“duck typing”)

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The “black magic” prejudice. var service = { /* @Secured(user = "ADMIN") */ deleteEverything: function () { // delete everything ... } } function run(service) { service.deleteEverything(); } In dynamic languages (also those running on the JVM) this concept is applied a lot! For framework implementors, type-safety is conceptually impossible. But with type information available, we are at least able to fail fast when generating code at runtime in case that types do not match. No type, no problem. (“duck typing”)

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class Method { Object invoke(Object obj, Object... args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException; } class Class { Method getDeclaredMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException; } Isn’t reflection meant for this?

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class Method { Object invoke(Object obj, Object... args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException; } class Class { Method getDeclaredMethod(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException; } Isn’t reflection meant for this? Reflection implies neither type-safety nor a notion of fail-fast. Note: there are no performance gains when using code generation over reflection! Thus, runtime code generation only makes sense for user type enhancement: While the framework code is less type safe, this type-unsafety does not spoil the user‘s code.

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(value("Hello World!")) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); assertThat(dynamicType.newInstance().toString(), is("Hello World!")); Byte Buddy: subclass creation

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class MyInterceptor { static String intercept() { return "Hello World"; } } Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(to(MyInterceptor.class)) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); Byte Buddy: invocation delegation

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class MyInterceptor { static String intercept() { return "Hello World"; } } Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(to(MyInterceptor.class)) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); Byte Buddy: invocation delegation

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class MyInterceptor { static String intercept() { return "Hello World"; } } identifies best match Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(to(MyInterceptor.class)) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); Byte Buddy: invocation delegation

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class MyInterceptor { static String intercept(@Origin Method m) { return "Hello World from " + m.getName(); } } Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(to(MyInterceptor.class)) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); provides arguments Byte Buddy: invocation delegation (2)

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class MyInterceptor { static String intercept(@Origin Method m) { return "Hello World from " + m.getName(); } } Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(to(MyInterceptor.class)) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); provides arguments Byte Buddy: invocation delegation (2)

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Annotations that are not on the class path are ignored at runtime. Thus, Byte Buddy’s classes can be used without Byte Buddy on the class path. class MyInterceptor { static String intercept(@Origin Method m) { return "Hello World from " + m.getName(); } } Class<?> dynamicType = new ByteBuddy() .subclass(Object.class) .method(named("toString")) .intercept(to(MyInterceptor.class)) .make() .load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER) .getLoaded(); provides arguments Byte Buddy: invocation delegation (2)

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@Origin Method|Class<?>|String Provides caller information @SuperCall Runnable|Callable<?> Allows super method call @DefaultCall Runnable|Callable<?> Allows default method call @AllArguments T[] Provides boxed method arguments @Argument(index) T Provides argument at the given index @This T Provides caller instance @Super T Provides super method proxy Byte Buddy: dependency injection

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class Foo { String bar() { return "bar"; } } Foo foo = new Foo(); new ByteBuddy() .redefine(Foo.class) .method(named("bar")) .intercept(value("Hello World!")) .make() .load(Foo.class.getClassLoader(), ClassReloadingStrategy.installedAgent()); assertThat(foo.bar(), is("Hello World!")); Byte Buddy: runtime Hot Swap

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class Foo { String bar() { return "bar"; } } Foo foo = new Foo(); new ByteBuddy() .redefine(Foo.class) .method(named("bar")) .intercept(value("Hello World!")) .make() .load(Foo.class.getClassLoader(), ClassReloadingStrategy.installedAgent()); assertThat(foo.bar(), is("Hello World!")); Byte Buddy: runtime Hot Swap

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class Foo { String bar() { return "bar"; } } Foo foo = new Foo(); new ByteBuddy() .redefine(Foo.class) .method(named("bar")) .intercept(value("Hello World!")) .make() .load(Foo.class.getClassLoader(), ClassReloadingStrategy.installedAgent()); assertThat(foo.bar(), is("Hello World!")); Byte Buddy: runtime Hot Swap

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class Foo { String bar() { return "bar"; } } Foo foo = new Foo(); new ByteBuddy() .redefine(Foo.class) .method(named("bar")) .intercept(value("Hello World!")) .make() .load(Foo.class.getClassLoader(), ClassReloadingStrategy.installedAgent()); assertThat(foo.bar(), is("Hello World!")); The instrumentation API does not allow introduction of new methods. This might change with JEP-159: Enhanced Class Redefiniton. Byte Buddy: runtime Hot Swap

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class Foo { String bar() { return "bar"; } } assertThat(new Foo().bar(), is("Hello World!")); Byte Buddy: Java agents

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class Foo { String bar() { return "bar"; } } assertThat(new Foo().bar(), is("Hello World!")); public static void premain(String arguments, Instrumentation instrumentation) { new AgentBuilder.Default() .rebase(named("Foo")) .transform( (builder, type) -> builder .method(named("bar")) .intercept(value("Hello World!")); ) .installOn(instrumentation); } Byte Buddy: Java agents

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class Foo { String bar() { return "bar"; } } assertThat(new Foo().bar(), is("Hello World!")); public static void premain(String arguments, Instrumentation instrumentation) { new AgentBuilder.Default() .rebase(named("Foo")) .transform( (builder, type) -> builder .method(named("bar")) .intercept(value("Hello World!")); ) .installOn(instrumentation); } Byte Buddy: Java agents

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class Foo { String bar() { return "bar"; } } assertThat(new Foo().bar(), is("Hello World!")); public static void premain(String arguments, Instrumentation instrumentation) { new AgentBuilder.Default() .rebase(named("Foo")) .transform( (builder, type) -> builder .method(named("bar")) .intercept(value("Hello World!")); ) .installOn(instrumentation); } Byte Buddy: Java agents

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class Foo { String bar() { return "bar"; } } assertThat(new Foo().bar(), is("Hello World!")); public static void premain(String arguments, Instrumentation instrumentation) { new AgentBuilder.Default() .rebase(named("Foo")) .transform( (builder, type) -> builder .method(named("bar")) .intercept(value("Hello World!")); ) .installOn(instrumentation); } Byte Buddy: Java agents

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Android makes things more complicated.

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Java virtual machine [stack, JIT] Android makes things more complicated.

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Java virtual machine [stack, JIT] Dalvik virtual machine [register, JIT] Android makes things more complicated.

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Java virtual machine [stack, JIT] Dalvik virtual machine [register, JIT] Android runtime [register, AOT] Android makes things more complicated.

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Java virtual machine [stack, JIT] Dalvik virtual machine [register, JIT] Android runtime [register, AOT] Android makes things more complicated. Solution: Embed the Android SDK’s dex compiler (Apache 2.0 license). Unfortunately, no recent version central repository deployments of Android SDK.

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Byte Buddy cglib Javassist Java proxy (1) 60.995 234.488 145.412 68.706 (2a) 153.800 804.000 706.878 973.650 (2b) 0.001 0.002 0.009 0.005 (3a) 172.126 1’850.567 1’480.525 625.778 n/a (3b) 0.002 0.003 0.019 0.027 n/a All benchmarks run with JMH, source code: https://github.com/raphw/byte-buddy (1) Extending the Object class without any methods but with a default constructor (2a) Implementing an interface with 18 methods, method stubs (2b) Executing a method of this interface (3a) Extending a class with 18 methods, super method invocation (3b) Executing a method of this class

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http://rafael.codes @rafaelcodes http://documents4j.com https://github.com/documents4j/documents4j http://bytebuddy.net https://github.com/raphw/byte-buddy