[java] What could cause java.lang.reflect.InvocationTargetException?

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?

This exception is thrown if the underlying method(method called using Reflection) throws an exception.

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

From the Javadoc of Method.invoke()

Throws: InvocationTargetException - if the underlying method throws an exception.

This exception is thrown if the method called threw an exception.

Use the getCause() method on the InvocationTargetException to retrieve the original exception.

This will print the exact line of code in the specific method, which when invoked, raised the exception:

try {

    // try code
    ..
    m.invoke(testObject);
    ..

} catch (InvocationTargetException e) {

    // Answer:
    e.getCause().printStackTrace();
} catch (Exception e) {

    // generic exception handling
    e.printStackTrace();
}

That InvocationTargetException is probably wrapping up your ArrayIndexOutOfBoundsException. There is no telling upfront when using reflection what that method can throw -- so rather than using a throws Exception approach, all the exceptions are being caught and wrapped up in InvocationTargetException.

The error vanished after I did Clean->Run xDoclet->Run xPackaging.

In my workspace, in ecllipse.

I had a java.lang.reflect.InvocationTargetException error from a statement calling a logger object in an external class inside a try / catch block in my class.

Stepping through the code in the Eclipse debugger & hovering the mouse over the logger statement I saw the logger object was null (some external constants needed to be instantiated at the very top of my class).

You can compare with the original exception Class using getCause() method like this :

try{
  ...
} catch(Exception e){
   if(e.getCause().getClass().equals(AssertionError.class)){
      // handle your exception  1
   } else {
      // handle the rest of the world exception 
   }
} 

1. List all jar files from the Eclipse Navigator mode
2. Verify that all the jar files are in binary mode

I was facing the same problem. I used e.getCause().getCause() then I found that it was because of wrong parameters I was passing. There was nullPointerException in fetching the value of one of the parameters. Hope this will help you.

This describes something like,

InvocationTargetException is a checked exception that wraps an exception thrown by an invoked method or constructor. As of release 1.4, this exception has been retrofitted to conform to the general purpose exception-chaining mechanism. The "target exception" that is provided at construction time and accessed via the getTargetException() method is now known as the cause, and may be accessed via the Throwable.getCause() method, as well as the aforementioned "legacy method."

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.