What could cause java.lang.reflect.InvocationTargetException?

java exception reflection invoke
user550413 picture user550413 · May 16, 2011 · Viewed 1M times · Source

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

Jon Skeet picture Jon Skeet · May 16, 2011

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.

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