What could cause java.lang.reflect.InvocationTargetException?

Question

Well, I've tried to understand and read what could cause it but I just can't get it:

I have this somewhere in my code:

 try{  ..  m.invoke(testObject);  ..  } catch(AssertionError e){  ...  } catch(Exception e){  ..  } 

Thing is that, when it tries to invoke some method it throws InvocationTargetException instead of some other expected exception (specifically ArrayIndexOutOfBoundsException). As I actually know what method is invoked I went straight to this method code and added a try-catch block for the line that suppose to throw ArrayIndexOutOfBoundsException and it really threw ArrayIndexOutOfBoundsException as expected. Yet when going up it somehow changes to InvocationTargetException and in the code above catch(Exception e) e is InvocationTargetException and not ArrayIndexOutOfBoundsException as expected.

What could cause such a behavior or how can I check such a thing?

Answer 1

You've added an extra level of abstraction by calling the method with reflection. The reflection layer wraps any exception in an InvocationTargetException, which lets you tell the difference between an exception actually caused by a failure in the reflection call (maybe your argument list wasn't valid, for example) and a failure within the method called.

Just unwrap the cause within the InvocationTargetException and you'll get to the original one.

Answer 2

The exception is thrown if

InvocationTargetException - if the underlying method throws an exception.

So if the method, that has been invoked with reflection API, throws an exception (runtime exception for example), the reflection API will wrap the exception into an InvocationTargetException.