Jersey ExceptionMapper, rely on another ExceptionMapper

Question

I have an ExceptionMapper which is part of a generic common library:

@Provider
public class GenericExceptionMapper implements ExceptionMapper<GenericException> {
    ...
}

Now, in my specific project, I have my own ExceptionMapper:

@Provider
public class SomeAdHocExceptionMapper implements ExceptionMapper<SomeAdHocException> {
    ...
}

I would like to convert the SomeAdHocException to GenericException and let GenericExceptionMapper be responsible for further processing. I tried the following two options, but both are not working:

[1] throw GenericException in SomeAdHocExceptionMapper:

@Provider
public class SomeAdHocExceptionMapper implements ExceptionMapper<SomeAdHocException> {
    public Response toResponse(SomeAdHocException e) {
        throw new GenericException(e);
    }
}

[2] inject GenericExceptionMapper into SomeAdHocExceptionMapper:

@Provider
public class SomeAdHocExceptionMapper implements ExceptionMapper<SomeAdHocException> {
    @Inject
    private GenericExceptionMapper mapper;

    public Response toResponse(SomeAdHocException e) {
        return mapper.toResponse(new GenericException(e));
    }
}

Both options are giving dependency excpetions.

How do I solve this?

score 0 · Accepted Answer · answered May 04 '17 at 20:04

Your first attempt won't work because only one exception mapper can be called for a single request. This is a safety feature to ensure that we don't run into infinite loops. Imagine XExceptionMapper throws a YException during processing and YExceptionMapper throws a XException during processing.

Your second attempt won't work because the mapper isn't injectable. You could just instantiate it though.

@Provider
public class SomeAdHocExceptionMapper implements ExceptionMapper<SomeAdHocException> {

    private final GenericExceptionMapper mapper = new GenericExceptionMapper();

    public Response toResponse(SomeAdHocException e) {
        return mapper.toResponse(new GenericException(e));
    }
}

Assuming there is such a constructor and that the generic mapper doesn't require any injections of it's own. If it does, you could make the mapper injectable.

public class AppConfig extends ResourceConfig {
    public AppConfig() {
        register(new AbstractBinder() {
            @Override
            protected void configure() {
                bindAsContract(GenericExceptionMapper.class);
            }
        });
    }
}

Then you would be able to inject it.

Jersey ExceptionMapper, rely on another ExceptionMapper

1 Answers1