关于Class的invokeDynamic指令 java7之Special Methods invokedynamic指令

（2）invokedynamic指令 https://www.cnblogs.com/wade-luffy/p/6058087.html

public class InDyTest {    
    public static void main(String[] args) {
        Runnable x = () -> {
            //System.out.println("Hello, World!"); 
        };
    }    
}

生成的Class结构如下：

Classfile /C:/Users/mazhi/Desktop/InDyTest.class
  Last modified 2018-7-5; size 986 bytes
  MD5 checksum 03d0c485e603b294e8de271d879c7b8f
  Compiled from "InDyTest.java"
public class com.test01.InDyTest
  SourceFile: "InDyTest.java"
  BootstrapMethods:
    0: #34 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/la                                                                                                                ng/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Lj                                                                                                                ava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/Meth                                                                                                                odType;)Ljava/lang/invoke/CallSite;
      Method arguments:
        #35 ()V
        #38 invokestatic com/test01/InDyTest.lambda$0:()V
        #39 ()V
  InnerClasses:
       public static final #45= #41 of #43; //Lookup=class java/lang/invoke/Meth                                                                                                                odHandles$Lookup of class java/lang/invoke/MethodHandles
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Class              #2             //  com/test01/InDyTest
   #2 = Utf8               com/test01/InDyTest
   #3 = Class              #4             //  java/lang/Object
   #4 = Utf8               java/lang/Object
   #5 = Utf8               <init>
   #6 = Utf8               ()V
   #7 = Utf8               Code
   #8 = Methodref          #3.#9          //  java/lang/Object."<init>":()V
   #9 = NameAndType        #5:#6          //  "<init>":()V
  #10 = Utf8               LineNumberTable
  #11 = Utf8               LocalVariableTable
  #12 = Utf8               this
  #13 = Utf8               Lcom/test01/InDyTest;
  #14 = Utf8               main
  #15 = Utf8               ([Ljava/lang/String;)V
  #16 = NameAndType        #17:#18        //  run:()Ljava/lang/Runnable;
  #17 = Utf8               run
  #18 = Utf8               ()Ljava/lang/Runnable;
  #19 = InvokeDynamic      #0:#16         //  #0:run:()Ljava/lang/Runnable;
  #20 = Utf8               args
  #21 = Utf8               [Ljava/lang/String;
  #22 = Utf8               x
  #23 = Utf8               Ljava/lang/Runnable;
  #24 = Utf8               lambda$0
  #25 = Utf8               SourceFile
  #26 = Utf8               InDyTest.java
  #27 = Utf8               BootstrapMethods
  #28 = Methodref          #29.#31        //  java/lang/invoke/LambdaMetafactory                                                                                                                .metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lan                                                                                                                g/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;                                                                                                                Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #29 = Class              #30            //  java/lang/invoke/LambdaMetafactory
  #30 = Utf8               java/lang/invoke/LambdaMetafactory
  #31 = NameAndType        #32:#33        //  metafactory:(Ljava/lang/invoke/Met                                                                                                                hodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invo                                                                                                                ke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava                                                                                                                /lang/invoke/CallSite;
  #32 = Utf8               metafactory
  #33 = Utf8               (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/St                                                                                                                ring;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke                                                                                                                /MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #34 = MethodHandle       #6:#28         //  invokestatic java/lang/invoke/Lamb                                                                                                                daMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/Str                                                                                                                ing;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/                                                                                                                MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #35 = MethodType         #6             //  ()V
  #36 = Methodref          #1.#37         //  com/test01/InDyTest.lambda$0:()V
  #37 = NameAndType        #24:#6         //  lambda$0:()V
  #38 = MethodHandle       #6:#36         //  invokestatic com/test01/InDyTest.l                                                                                                                ambda$0:()V
  #39 = MethodType         #6             //  ()V
  #40 = Utf8               InnerClasses
  #41 = Class              #42            //  java/lang/invoke/MethodHandles$Loo                                                                                                                kup
  #42 = Utf8               java/lang/invoke/MethodHandles$Lookup
  #43 = Class              #44            //  java/lang/invoke/MethodHandles
  #44 = Utf8               java/lang/invoke/MethodHandles
  #45 = Utf8               Lookup
{
  public com.test01.InDyTest();
    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 4: 0
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0       5     0  this   Lcom/test01/InDyTest;

  public static void main(java.lang.String[]);
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=1, locals=2, args_size=1
         0: invokedynamic #19,  0             // InvokeDynamic #0:run:()Ljava/la                                                                                                                ng/Runnable;
         5: astore_1
         6: return
      LineNumberTable:
        line 7: 0
        line 10: 6
      LocalVariableTable:
        Start  Length  Slot  Name   Signature
               0       7     0  args   [Ljava/lang/String;
               6       1     1     x   Ljava/lang/Runnable;
}

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodType;
import static java.lang.invoke.MethodHandles.lookup;

public class TestMethod {
	static class ClassA {
		public void println(String s) {
			System.out.println(s);
		}
	}

	public static void main(String[] args) throws Throwable {
		Object obj = System.currentTimeMillis() % 2 == 0 ? System.out : new ClassA();
		/* 
		 * 无论obj最终是哪个实现类，下面这句都能正确调用到println方法
		 **/
		getPrintlnMH(obj).invokeExact("icyfenix");
	}

	private static MethodHandle getPrintlnMH(Object reveiver) throws Throwable {
		/*
		 * MethodType：代表“方法类型”，包含了方法的返回值（methodType（）的第一个参数）
		 * 和具体参数（methodType（） 第二个及以后的参数）
		 */
		MethodType mt = MethodType.methodType(void.class, String.class);
		/*
		 * lookup（）方法来自于MethodHandles.lookup，这句的作用是在指定类中查找符合给定的方法名称、方法类型，
		 * 并且符合调用权限的方法句柄
		 * 因为这里调用的是一个虚方法，按照Java语言的规则，方法第一个参数是隐式的，代表该方法的接收者，也即是this指向的对象，
		 * 这个参数以前是放在参数列表中进行传递的，而现在提供了bindTo（）方法来完成这件事情
		 */
		return lookup().findVirtual(reveiver.getClass(), "println", mt).bindTo(reveiver);
	}
}

import static java.lang.invoke.MethodHandles.lookup;
import java.lang.invoke.CallSite;
import java.lang.invoke.ConstantCallSite;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;

public class InvokeDynamicTest {
	public static void main(String[] args) throws Throwable {
		INDY_BootstrapMethod().invokeExact("icyfenix");
	}

	public static void testMethod(String s) {
		System.out.println("hello String：" + s);
	}

	public static CallSite BootstrapMethod(
			MethodHandles.Lookup lookup, 
			String name, 
			MethodType mt) throws Throwable {
		return new ConstantCallSite(
				lookup.findStatic(InvokeDynamicTest.class, name, mt));
	}

	private static MethodType MT_BootstrapMethod() {
		return MethodType.fromMethodDescriptorString(
				"(Ljava/lang/invoke/MethodHandles $Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;",
				null);
	}

	private static MethodHandle MH_BootstrapMethod() throws Throwable {
		return lookup().findStatic(
				InvokeDynamicTest.class, 
				"BootstrapMethod", 
				MT_BootstrapMethod());
	}

	private static MethodHandle INDY_BootstrapMethod() throws Throwable {
		CallSite cs = (CallSite) MH_BootstrapMethod().invokeWithArguments(
				lookup(), 
				"testMethod",
				MethodType.fromMethodDescriptorString("(Ljava/lang/String;)V", null));
		return cs.dynamicInvoker();
	}
}

import static java.lang.invoke.MethodHandles.lookup;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodType;

public class Test02 {
	class GrandFather {
		void thinking() {
			System.out.println("i am grandfather");
		}
	}

	class Father extends GrandFather {
		void thinking() {
			System.out.println("i am father");
		}
	}

	class Son extends Father {
		void thinking() {
			try {
				MethodType mt = MethodType.methodType(void.class);
				MethodHandle mh = lookup().findVirtual(
										GrandFather.class, 
										"thinking", 
										mt)
						.bindTo(new Test02().new GrandFather());
				mh.invokeExact();
			} catch (Throwable e) {
			}
		}
	}

	public static void main(String[] args) {
		(new Test02().new Son()).thinking();
	}
}

关于Class的invokeDynamic指令 java7之Special Methods invokedynamic指令

猜你喜欢