HTTP Status 500 - Internal Server Error

Question

After trying to make a call in the Glasfish Webservice is occurring the error below, I am trying to make a call in the Webservice Rest Json, in the XML Rest call it runs normally.

package br.com.devmedia.ws.rest.example1;

import java.util.Random;

import javax.ws.rs.GET;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.UriInfo;

@Path("ceprest")
public class CepRestWS {

    @Context
    private UriInfo context;

    public CepRestWS() {
    }

    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @Path("getCep/{cep}")
    public Cep getCep(@PathParam("cep") String cep) {
        Cep toReturn = new Cep();
        toReturn.setCep(cep);
        toReturn.setBairro("Bairro " + new Random().nextInt());
        toReturn.setNumero(new Random().nextInt());
        toReturn.setRua("Rua que sempre " + new Random().nextInt());
        toReturn.setUf("PR");
        return toReturn;
    }

}