Java - Throwable to Exception

Question

I am currently using the play2 framework.

I have several classes which are throwing exceptions but play2s global onError handler uses throwable instead of an exception.

for example one of my classes is throwing a NoSessionException. Can I check a throwable object if it is a NoSessionException ?

Bunnybunow

Throwable is the superclass of all exceptions. You can catch a throwable and then interrogate its class to see if it's a NoSessionException or whatever. – Lactoprotein

thank you all for the fast answer. – Bunnybunow

Of course, you can also catch specifically NoSessionException, and then pass it to an interface that expects a Throwable -- since Throwable is the superclass the interface will accept NoSessionException. – Lactoprotein

(And if you do catch all Throwables, you shouldn't simply ignore the ones you don't select, but rather you should re-throw them.) – Lactoprotein

Answer 1

You can use instanceof to check it is of NoSessionException or not.

Example:

if (exp instanceof NoSessionException) {
...
}

Assuming exp is the Throwable reference.

Farmann

Answer 2

Just make it short. We can pass Throwable to Exception constructor.

 @Override
 public void onError(Throwable e) {
    Exception ex = new Exception(e);
 }               

See this Exception from Android

Khoury

Stack trace data is lost doing this however :-( – Honewort

@BrianKnoblauch Android also provide another constructor to keep the StackTrace. Exception (String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) – Khoury

Answer 3

Can I check a throwable object if it is a NoSessionException ?

Sure:

Throwable t = ...;
if (t instanceof NoSessionException) {
    ...
    // If you need to use information in the exception
    // you can cast it in here
}

Aureaaureate

Answer 4

Throwable is a class which Exception – and consequently all subclasses thereof – subclasses. There's nothing stopping you from using instanceof on a Throwable.

Erased

Answer 5

In addition to checking if its an instanceof you can use the try catch and catch NoSessionException

try {
    // Something that throws a throwable
} catch (NoSessionException e) {
    // Its a NoSessionException 
} catch (Throwable t) {
    // catch all other Throwables
}

Syndic

Answer 6

If you are using Spring, then why not go for a specific exception handler for specific type.

You can have one GlobalException handler and tag it to your controller

@ControllerAdvice(assignableTypes = {YourController.class})
public class MyGlobalExceptionHandler {

Then you can have specific handler methods to handle specific exception.

for e.g. below is handling specific ServerWebInputException

  @ExceptionHandler(ServerWebInputException.class)
      public ResponseEntity<YourResponseObject> handleValidationError(final ServerWebInputException badRequest) {
    }

and you can have a generic Throwable handler

@ExceptionHandler(Throwable.class)
  public ResponseEntity<YourResponseObject> handleThrowable(final Throwable throwable) {

This would be a clean solution.

Deas