JAX-RS - support query param 'format'

[rsoika]

Extend the rest api with a new optional query param 'format' to allow optional force output in XML or JSON. Currenty we only support the header param 'accept'

Using this param we can switch the ouput format:

@GET
@Produces({ MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON })
public Response service(@QueryParam("format") String format) {
    return Response
            // Set the status and Put your entity here.
            .ok(entity)
            // Add the Content-Type header to tell Jersey which format it should marshall the entity into.
            .header(HttpHeaders.CONTENT_TYPE, "json".equals(format) ? MediaType.APPLICATION_JSON : MediaType.APPLICATION_XML)
            .build();
}

See: https://stackoverflow.com/questions/18026296/jersey-how-to-generate-json-and-xml-output-depending-on-url-param/35112400