Error 415 when posting with json

I have a CREST REST application that responded in XML, however, I want to change it and get it to respond to JSON.

I can do the GET in the restclient, but the POST, PUT and DELETE do not, it gives the error 415 Unsupported Media Type. What else should I include in my code for it to work?

Follow the code below:

package pojo;

import javax.xml.bind.annotation.XmlRootElement;

@XmlRootElement
public class Aluno {
    private int matricula;
    private String nome;
    private Endereco endereco;
    private Curso curso;

    public Aluno() {

    }

    public Aluno(int matricula, String nome, Endereco endereco, Curso curso) {
        super();
        if (!nome.isEmpty())
        {
            this.matricula = matricula;
            this.nome = nome;
            this.endereco = endereco;
            this.curso = curso; 
        }
    }

    public int getMatricula() {
        return matricula;
    }

    public void setMatricula(int matricula) {
        this.matricula = matricula;
    }

    public String getNome() {
        return nome;
    }

    public void setNome(String nome) {
        this.nome = nome;
    }

    public Endereco getEndereco() {
        return endereco;
    }

    public void setEndereco(Endereco endereco) {
        this.endereco = endereco;
    }

    public Curso getCurso() {
        return curso;
    }

    public void setCurso(Curso curso) {
        this.curso = curso;
    }

}

My CourseResource:

package resources;

import java.net.URI;
import java.net.URISyntaxException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

import javax.servlet.http.HttpServletResponse;
import javax.ws.rs.Consumes;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.core.MediaType;
//import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;

import com.google.gson.Gson;

import pojo.Curso;
import client.EscolaService;

@Path("curso")
@Consumes(MediaType.APPLICATION_JSON)
@Produces(MediaType.APPLICATION_JSON)
public class CursoResource {

    private EscolaService escolaService;

    public CursoResource() {
        this.escolaService = new EscolaService();
    }

    @GET
    @Path("{codigo}")
    public Response buscarCurso(@PathParam("codigo") String codigo) {
        Curso curso = escolaService.buscarCurso(new Integer(codigo).intValue());
        if (curso == null) {
            return Response.status(HttpServletResponse.SC_NOT_FOUND).build();
        }

        System.out.println(new Gson().toJson(curso));

        Response resposta = Response.ok(new Gson().toJson(curso)).build();
        return resposta;// coloquei porque estava dando erro
    }

    @POST
    @Consumes("application/json")
    public Response cadastrarCurso(Curso curso) {
        if ((curso.getCodigo() > 0) && (curso.getCodigo() < 100))
        {
            curso = escolaService.cadastrarCurso(curso);
            try {
                return Response.created(new URI("" + curso.getCodigo())).build();
            } catch (URISyntaxException e) {
                throw new RuntimeException(e);
            }
        }
        Response resposta = Response.ok(new Gson().toJson(curso)).build();
        return resposta.noContent().build();
    }

    @PUT
    public Response alterarCurso(Curso curso) {
        curso = escolaService.alterarCurso(curso);
        try {
            return Response.created(new URI("" + curso.getCodigo())).build();
        } catch (URISyntaxException e) {
            throw new RuntimeException(e);
        }
    }

    @DELETE
    @Path("{codigo}")
    public Response removerCurso(@PathParam("codigo") String codigo) {
        boolean excluir = escolaService.removerCurso(new Integer(codigo)
                .intValue());
        if (excluir == false) {
            return Response.status(HttpServletResponse.SC_NOT_FOUND).build();
        }
        Response resposta = Response.ok().build();
        return resposta;
    }

    @GET
    @Produces("text/plain")
    public String listarCursos() {
        List<Integer> codigos = new ArrayList<Integer>();
        List<String> nomes = new ArrayList<String>();
        for (Iterator<Curso> it = escolaService.listarCursos().iterator(); it
                .hasNext();) {
            Curso curso = (Curso) it.next();
            codigos.add(curso.getCodigo());
            nomes.add(curso.getNome());

        }
        String separador = System.getProperty("line.separator");
        return ("Cursos" +separador+ separador+ "Codigos: " + codigos.toString() +separador+ "Nomes: " + nomes.toString());
    }

}