为什么在使用reflection调用方法时,“对象不是声明类的实例”?

public class Shared { public static void main(String arg[]) throws SecurityException, NoSuchMethodException, IllegalArgumentException, IllegalAccessException, InvocationTargetException { Shared s1 = new Shared(); Object obj[] = new Object[2]; obj[0] = "object1"; obj[1] = "object2"; s1.testParam(null, obj); Class param[] = new Class[2]; param[0] = String.class; param[1] = Object[].class; //// how to define the second parameter as array Method testParamMethod = s1.getClass().getDeclaredMethod("testParam", param); testParamMethod.invoke("", obj); ///// here getting error } public void testParam(String query,Object ... params){ System.out.println("in the testparam method"); } } 

这是输出:

 in the testparam method Exception in thread "main" java.lang.IllegalArgumentException: object is not an instance of declaring class at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.lang.reflect.Method.invoke(Unknown Source) at pkg.Shared.main(Shared.java:20) 

通过reflection调用方法时,需要将调用方法的对象作为Method#invoke的第一个参数传递。

 // equivalent to s1.testParam("", obj) testParamMethod.invoke(s1, "", obj); 
  testParamMethod.invoke("", obj); ///// here getting error 

要调用的第一个参数必须是要在其上调用它的对象:

  testParamMethod.invoke(s1, "", obj);