Custom exception class does not catch exceptions

Question

I have a Custom exception class which extends Exception class (like below).

public class SomeABCException extends Exception

But, when I use this SomeABCException in all places where I previously used Exception in the catch block, it does not catch the Exceptions even after it extends Exception class itself.

E.g. if a parent/caller method has a catch block as below

catch (Exception e) {
    TODO something;
}

and if I have a child method as below in which I am running some database queries.

try {
    Some database queries;
} catch (SomeABCException e) {
    throw new SomeABCException (e.getMessage(),"I/O or SQL_EXCEPTION");
}

Here if the sql connection fails, the catch is not able to catch the exceptions, rather it gets caught in the parent/callers catch block which uses System.Exception to catch it.

During the debug, it does not go to the throw in the catch block on child method.

Please explain, I do not understand it.

Answer 1

I believe you are thinking backwards. Instances of Exception will only catch exceptions that are subclasses, or instances of it. So, since Exception is a superclass of SomeABCException, the SQLException will NOT be caught.

Answer 2

Try this instead:

try {
    //Some database queries; -> this will throw Exception
} catch (Exception e) {
    throw new SomeABCException (e.getMessage(),"I/O or SQL_EXCEPTION");
}

You are catching SomeABCException when your "some database queries" are not throwing that kind of exception (maybe some SQLException or something like that)