使用invokedynamic实现多个调度

问题描述

我想知道Java7的新的 invokedynamic 字节码指令是否可以用于实现 Java语言。 java.lang.invoke下的新API是否有助于执行此类操作？

我正在考虑的情况如下。 （这看起来像访客设计模式的应用案例，但可能有原因，这不是一个可行的选择。）

  class A {} 
 class A1 extends A {} 
 class A2 extends A {} 
 
 class SomeHandler {
 private void doHandle（A1 a1）{.. 。} 
 private void doHandle（A2 a2）{...} 
 private void doHandle（A a）{...} 
 
 public void handle（A a）{ 
 MultipleDispatch.call（this，doHandle，a）; 
} 
} 
  

库类 MultipleDispatch 然后会做一些类似的事情：

  class MultipleDispatch {
 
 public静态对象调用（Object receiver，String method，Object ... arg）{
 //这样的字节码
 #invokeDynamicdoHandlesomeBootstrap
} 
 
 static CallSite someBootstrap {
 //解析动态方法调用。 
} 
} 
  

（我知道，但可以以纯Java的方式实现吗？）

解决方案

由于我没有invokedynamic的经验，我不知道性能和类型安全性会有多好，但只能给一些指针：

• 提供多个通过invokedynamic调度（请参阅多调度/ src / invokedynamicmultipledispatch /）;


• Charles Oliver Natter具有。幻灯片根本不详细，但我想我在一个关于JAX2012的视频或播客中看到更多的细节，我现在找不到。


• 是没有invokedynamic的替代方法。 和有很多性能信息/基准测试（在完成您的分析之后，它们是一个很好的阅读）;

I wondered if Java7's new invokedynamic bytecode instruction could be used to implement multiple dispatch for the Java language. Would the new API under java.lang.invoke be helpful to perform such a thing?

The scenario I was thinking about looked as follows. (This looks like an application case for the visitor design pattern, but there may be reasons that this is not a viable option.)

class A {}
class A1 extends A {}
class A2 extends A {}

class SomeHandler {
    private void doHandle(A1 a1) { ... }
    private void doHandle(A2 a2) { ... }
    private void doHandle(A a) { ... }

    public void handle(A a) {
        MultipleDispatch.call(this, "doHandle", a);
    }
}

The library class MultipleDispatch would then do something of the kind:

class MultipleDispatch {

    public static Object call(Object receiver, String method, Object...arg) {
        // something like that in byte code
        #invokeDynamic "doHandle" "someBootstrap"
    }

    static CallSite someBootstrap {
        // resolve that dynamic method call.
    }
}

(I am aware of MultiJava, but can this be achieved in a Java-pure fashion?)

解决方案

Since I have no experience with invokedynamic, I do not know how good the performance and type-safety would be, but can only give some pointers:

• the Da Vinci Machine Project offers multiple dispatch via invokedynamic (see Multiple Dispatch/src/invokedynamicmultipledispatch/);
• Charles Oliver Natter has talked about applications of invokedynamic on JAX2012. The slides do not go into details at all, but I think I came across more details in a video or podcast talking about JAX2012, which I cannot find right now.
• Christopher Dutchyn's JVM Multiple Dispatch is an alternative approach without invokedynamic. His COOTS '01 Paper and these slides have a lot of performance information/benchmarking (and are a good read after you've finished your disseration ;)

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