Jersey ParamConverter exceptions not handled by ExceptionMapper

Question

Per title, exceptions thrown from a ParamConverter are NOT handled the way I expect.

With an ExceptionMapper:

@Provider
public class MyExceptionMapper implements ExceptionMapper<MyException> {
    @Override
    public Response toResponse(MyException exception) {
        return Response.serverError().entity( "It triggered" ).build();
    }
}

and ParamConverter:

@Provider 
(boilerplate junk)
    @Override
    public DateTime fromString(String value) {
        throw new MyException("convert");
    }

It does NOT return the "It triggered" text in a 500 error, but rather a 404.

Anticipated question : Are both providers registered?

Yes - If I throw "MyException" from a resource (within 'regular' code) it works as expected. I can also convert see the stacktrace with the "convert" message.

Is there any way to make exceptions from ParamConverters be handled by the ExceptionMapper?

I am using jersey 2.3.1, along with spring-jersey, launched in a jetty container 9.1.0.RC0

Paul Samsotha Paul Samsotha · Accepted Answer · 2015-09-13T17:53:59

Seem from reading this, the JAX-RS spec says the implementor should wrap unhandled exceptions in a NotFoundException (404) for @QueryParam and @PathParam, and from what I tested a 400, (I'm guessing BadRequestException) for @FormParam.

"if the field or property is annotated with @MatrixParam, @QueryParam or @PathParam then an implementation MUST generate an instance of NotFoundException (404 status) that wraps the thrown exception and no entity"

A couple ways I can see handling the exception, is to

Just handle it in the ParamConverter, e.g.

return new ParamConverter<T>() {

    @Override
    public T fromString(String string) {
        try {
            return (T)new MyObject().setValue(string);
        } catch (MyException ex) {
            Response response = Response.serverError().entity("Boo").build()
            throw new WebApplicationException(response);
        }
    }

    @Override
    public String toString(T t) {
        return t.toString();
    }  
};

Or just have your exception extend WebApplicationException, and return the Response there. e.g.

public class MyException extends WebApplicationException {

    public MyException(String message) {
        super(Response.serverError().entity(message).build());
    }
}

Jersey ParamConverter exceptions not handled by ExceptionMapper

2 Answers