Jersey/JAX-RS ExceptionMappers and Inheritance

Question

I'm using Jersey/JAX-RS to implement a RESTful web service. I have a question about the ExceptionMapper interface, which doesn't appear to be documented anywhere.

Say I have the following custom (extend RuntimeException) exceptions:

• FizzException extends RuntimeException
• BuzzException extends FizzException

Now let's say that I want my exception mappers to perform the following Exception-to-Response mappings:

• FizzException actually maps to an HTTP 404 NOT FOUND
• BuzzException maps to an HTTP 403 UNAUTHORIZED
• Everything else maps to an HTTP 500 INTERNAL SERVER ERROR

So, if I understand the API correctly, I need to implement 3 different exception mappers:

@Provider
public class DefaultExceptionMapper implements ExceptionMapper<Exception> {
    @Override
    Response toResponse(Exception exc) {
        // Map to HTTP 500
    }
}

@Provider
public class FizzExceptionMapper implements ExceptionMapper<FizzException> {
    @Override
    Response toResponse(Exception exc) {
        // Map to HTTP 404
    }
}

@Provider
public class BuzzExceptionMapper implements ExceptionMapper<BuzzException> {
    @Override
    Response toResponse(Exception exc) {
        // Map to HTTP 403
    }
}

However, this has me curious: since we have exception class inheritance going on, which mappers will actually fire? For instance:

• BuzzException extends FizzException, which ultimately extends Exception. So, if a BuzzException is thrown, which mapper will fire: BuzzExceptionMapper, FizzExceptionMapper or DefaultExceptionMapper?
• The other way around: when an Exception is thrown, since a BuzzException is, ultimately, an Exception, which mapper fires: BuzzExceptionMapper, FizzExceptionMapper or DefaultExceptionMapper?

Answer 1

Most specific exception mapper will be called.

So in your case :

• BuzzException will be mapped by BuzzExceptionMapper
• FizzException will be mapped by FizzExceptionMapper
• others Exception will be mapped by DefaultExceptionMapper