Java 反射调用具有通用参数的方法

Question

如何通过反射调用方法，当它具有通用参数时，如下面的片段 -

@Test
    public void testOptional() throws NoSuchMethodException, InvocationTargetException,
            IllegalAccessException
    {
        AtomicReference<ClassA> atomicReference = new AtomicReference<>(new ClassA());
        ClassB classB = new ClassB();

        Method method = MyTest.class.getDeclaredMethod("doSomething", AtomicReference.class, ClassB.class);
        method.setAccessible(true);
        method.invoke(atomicReference, classB);
    }

    private void doSomething(AtomicReference<ClassA> classA, ClassB classB){

        System.out.println("Hi do not poke me, I am working!");
    }

它给了我-

java.lang.IllegalArgumentException: object is not an instance of declaring class

Answer 1

doSomething方法是MyTest class 的一部分。 Method::invoke必须接受三个参数：

• MyTest class 的实例，将在其上调用该方法。
• AtomicReference的实例
• B 类的ClassB

所以它应该是这样的：

public void testOptional() throws NoSuchMethodException, InvocationTargetException,
            IllegalAccessException, InvocationTargetException {
        AtomicReference<ClassA> atomicReference = new AtomicReference<>(new ClassA());
        ClassB classB = new ClassB();

        MyTest myTest = new MyTest(); // here we create the object

        Method method = MyTest.class.getDeclaredMethod("doSomething", AtomicReference.class, ClassB.class);
        method.setAccessible(true);
        method.invoke(myTest, atomicReference, classB); //we invoke doSomething on myTest object with parameters
}

还要记住 generics 在编译时被擦除。 所以每个泛型类型在运行时都是Object 。