Validate if method exists in the webservice and customize return message

Question

I am creating a webservice Rest, and it is working properly, but there is a situation that I could not handle: if the provided url is searching for a non-existent method, the requester is redirected to my system’s error screen, I would like to display a customized message. Follows description:

url1 (valid): https://127.0.0.1/system/Ws/example/query 1? param1=test 1&param2=test 2

url (invalid): https://127.0.0.1/system/Ws/example/query 2

I would like the system to display a custom message when receiving a different url than url1, rather than redirecting to the page screen not found. However, how should I create a method to intercept and validate the url, and the given path does not exist in my class?

@Path("/ws/exemplo")
public class exemploResource {

    //único método implementado atualmente
    @GET()
    @Produces("text/plain")
    @Path("consulta1")
    public String consulta1(@QueryParam("param1") final String param1,
            @QueryParam("param2") final String param2,
            final @Context HttpServletRequest request) {
   ...
   }

Answer 1

I found a treatment tip (unfortunately I lost the reference link) and adapted for my use, creating the following method:

@GET()
@Produces("text/plain")
@Path("{url}")
public String validaServico (@PathParam("url") final String url) {
    //metodosExistentes é uma lista com todos os métodos existentes
    if (this.metodosExistentes.contains(url))
        return "";
    else
    {
        //omiti parte do código de setar mensagem e criar xml de retorno 
        //por não ser pertinente ao assunto
        erro.setDeErro("Consulta desejada não encontrada.");
        return XmlUtil.objectToXml(erro);
    }
}

Note that the first condition only exists to maintain the validation method structure, because if the given url is valid (i.e., there is a method), the correct method will be called and my validation method will not be triggered.