如何链接MethodHandle调用？

Question

我有一个问题，我有多个具有相同签名的方法(都返回void)。我希望能够组合这些方法的methodHandles，以获得依次调用每个方法的methodHandle。

我想要做到这一点的唯一方法是使用guardWithTest，我有一个如何在https://gist.github.com/gregw/b6c926fb44fd9a45b2c5afccaf7dcbf4上工作的示例：

但代码的本质是：‘java

    TestMethodHandle test = new TestMethodHandle();

    MethodHandle callA = MethodHandles.lookup().findVirtual(TestMethodHandle.class,"callA", methodType(Void.TYPE, String.class, Integer.TYPE)).bindTo(test);
    MethodHandle callB = MethodHandles.lookup().findVirtual(TestMethodHandle.class,"callB", methodType(Void.TYPE, String.class, Integer.TYPE)).bindTo(test);
    MethodHandle callC = MethodHandles.lookup().findVirtual(TestMethodHandle.class,"callC", methodType(Void.TYPE, String.class, Integer.TYPE)).bindTo(test);

    MethodHandle asGuard = MethodHandles.lookup().findStatic(TestMethodHandle.class,"alwaysTrue", MethodType.methodType(Boolean.TYPE));
    MethodHandle guardA = MethodHandles.filterReturnValue(callA,asGuard);
    MethodHandle guardB = MethodHandles.filterReturnValue(callB,asGuard);
    MethodHandle guardC = MethodHandles.filterReturnValue(callC,asGuard);

    MethodHandle empty = empty(methodType(Void.TYPE, String.class, Integer.TYPE));

    MethodHandle invokeC = MethodHandles.guardWithTest(guardC,empty,empty);
    MethodHandle invokeBC = MethodHandles.guardWithTest(guardB,invokeC,empty);
    MethodHandle invokeABC = MethodHandles.guardWithTest(guardA,invokeBC,empty);

    invokeABC.invoke("chained", 2);

有没有更简单的方法来做这件事？

补充问题...我应该这样做吗?还是在一组方法句柄上调用methodHandles in循环会同样快？

Answer 1

我认为这样可能会更好：

    MethodHandle callA = MethodHandles.lookup().findVirtual(TestMethodHandle.class,"callA", methodType(Void.TYPE, String.class, Integer.TYPE)).bindTo(test);
    MethodHandle callB = MethodHandles.lookup().findVirtual(TestMethodHandle.class,"callB", methodType(Void.TYPE, String.class, Integer.TYPE)).bindTo(test);
    MethodHandle callC = MethodHandles.lookup().findVirtual(TestMethodHandle.class,"callC", methodType(Void.TYPE, String.class, Integer.TYPE)).bindTo(test);

    MethodHandle foldedABC = MethodHandles.foldArguments(MethodHandles.foldArguments(callC,callB),callA);
    foldedABC.invoke("folded", 42);