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 ?

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. — Hot Licks, Sep 10 '12 at 20:47
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. — Hot Licks, Sep 10 '12 at 20:50
(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.) — Hot Licks, Sep 10 '12 at 20:56

score 53 · Accepted Answer · answered Sep 10 '12 at 20:46

53

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

Example:

if (exp instanceof NoSessionException) {
...
}

Assuming exp is the Throwable reference.

answered Sep 10 '12 at 20:46

kosa

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score 52 · Answer 2 · edited Jul 02 '18 at 13:45

52

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

edited Jul 02 '18 at 13:45

toto_tata

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answered Jan 12 '17 at 07:43

THANN Phearum

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Stack trace data is lost doing this however :-( – Brian Knoblauch Feb 08 '18 at 19:03
@BrianKnoblauch Android also provide another constructor to keep the StackTrace. Exception (String message, Throwable cause, boolean enableSuppression, boolean writableStackTrace) – THANN Phearum Mar 27 '18 at 14:39

score 16 · Answer 3 · answered Sep 10 '12 at 20:46

16

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
}

answered Sep 10 '12 at 20:46

Jon Skeet

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score 6 · Answer 4 · answered Sep 10 '12 at 20:46

6

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

answered Sep 10 '12 at 20:46

Matt Ball

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score 6 · Answer 5 · answered Sep 10 '12 at 20:51

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
}

score 0 · Answer 6 · answered Jun 14 '22 at 13:01

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.

Java - Throwable to Exception

6 Answers6

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