如何获取 Java 8 方法引用的 MethodInfo? [英] How to get the MethodInfo of a Java 8 method reference?

问题描述

请看下面的代码:

Method methodInfo = MyClass.class.getMethod("myMethod");

这可行，但方法名称作为字符串传递，因此即使 myMethod 不存在也会编译.

This works, but the method name is passed as a string, so this will compile even if myMethod does not exist.

另一方面，Java 8 引入了方法引用特性.它在编译时检查.可以使用此功能获取方法信息吗?

On the other hand, Java 8 introduces a method reference feature. It is checked at compile time. It is possible to use this feature to get method info?

printMethodName(MyClass::myMethod);

完整示例:

@FunctionalInterface
private interface Action {

    void invoke();
}

private static class MyClass {

    public static void myMethod() {
    }
}

private static void printMethodName(Action action) {
}

public static void main(String[] args) throws NoSuchMethodException {
    // This works, but method name is passed as a string, so this will compile
    // even if myMethod does not exist
    Method methodInfo = MyClass.class.getMethod("myMethod");

    // Here we pass reference to a method. It is somehow possible to
    // obtain java.lang.reflect.Method for myMethod inside printMethodName?
    printMethodName(MyClass::myMethod);
}

换句话说，我想要一个与以下 C# 代码等效的代码:

In other words I would like to have a code which is the equivalent of the following C# code:

    private static class InnerClass
    {
        public static void MyMethod()
        {
            Console.WriteLine("Hello");
        }
    }

    static void PrintMethodName(Action action)
    {
        // Can I get java.lang.reflect.Method in the same way?
        MethodInfo methodInfo = action.GetMethodInfo();
    }

    static void Main()
    {
        PrintMethodName(InnerClass.MyMethod);
    }

推荐答案

不，没有可靠的、受支持的方法来做到这一点.您将方法引用分配给函数式接口的实例，但该实例是由 LambdaMetaFactory 制作的，并且无法深入其中以找到您最初绑定的方法.

No, there is no reliable, supported way to do this. You assign a method reference to an instance of a functional interface, but that instance is cooked up by LambdaMetaFactory, and there is no way to drill into it to find the method you originally bound to.

Java 中的 Lambda 和方法引用的工作方式与 C# 中的委托截然不同.对于一些有趣的背景，请阅读 invokedynamic.

Lambdas and method references in Java work quite differently than delegates in C#. For some interesting background, read up on invokedynamic.

此处的其他答案和评论表明，目前可以通过一些额外的工作来检索绑定方法，但请确保您了解注意事项.

Other answers and comments here show that it may currently be possible to retrieve the bound method with some additional work, but make sure you understand the caveats.

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