X-FACEBOOK-PLATFORM authentication with SMACK Java

First post here so please be gentle. I'm building a facebook chat client, using Smack library. I'm using X-FACEBOOK-PLATFORM method in order not to save any passwords. I had it working properly using oauth 1.0, and want to change it to 2.0, cause of the october 1st deadline ;p. From what I understand the only thing I'd have to do in order to migrate to 2.0 is removing "sig" and "session_key" parameters and adding an "access_token" parameter, but I'm getting an "SASL authentication X-FACEBOOK-PLATFORM failed: not-authorized:". I'm using this custom SASLMechanism class:

package smackresearching;
import java.io.IOException;
import java.net.URLEncoder;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.Map;

import javax.security.sasl.Sasl;

import org.jivesoftware.smack.SASLAuthentication;
import org.jivesoftware.smack.XMPPException;
import org.jivesoftware.smack.sasl.SASLMechanism;
import org.jivesoftware.smack.util.Base64;

public class SASLXFacebookPlatformMechanism extends SASLMechanism {

    public static final String NAME = "X-FACEBOOK-PLATFORM";
    private String apiKey = "";
        private String accessToken = "";


    /**
     * Constructor.
     */
    public SASLXFacebookPlatformMechanism(SASLAuthentication saslAuthentication) {
            super(saslAuthentication);
    }

    @Override
    protected void authenticate() throws IOException, XMPPException {
        // Send the authentication to the server
        getSASLAuthentication().send(new AuthMechanism(getName(), ""));
    }

    @Override
    public void authenticate(String apiKey, String host, String accessToken) throws IOException, XMPPException {
        this.apiKey = apiKey;
        this.accessToken = accessToken;
        this.hostname = host;

        String[] mechanisms = { "DIGEST-MD5" };
        Map<String, String> props = new HashMap<String, String>();
        this.sc = Sasl.createSaslClient(mechanisms, null, "xmpp", host, props, this);
        authenticate();
    }

    @Override
    protected String getName() {
            return NAME;
    }

    @Override
    public void challengeReceived(String challenge) throws IOException {
        byte[] response = null;

        if (challenge != null) {
                    String decodedChallenge = new String(Base64.decode(challenge));
                    Map<String, String> parameters = getQueryMap(decodedChallenge);

                    String version = "1.0";
                    String nonce = parameters.get("nonce");
                    String method = parameters.get("method");

                    long callId = new GregorianCalendar().getTimeInMillis() / 1000L;

                    String composedResponse = "api_key=" + URLEncoder.encode(apiKey, "utf-8")
                                                                            + "&call_id=" + callId
                                                                            + "&method=" + URLEncoder.encode(method, "utf-8")
                                                                            + "&nonce=" + URLEncoder.encode(nonce, "utf-8")
                                                                            + "&access_token=" + URLEncoder.encode(accessToken, "utf-8")
                                                                            + "&v=" + URLEncoder.encode(version, "utf-8");

                    response = composedResponse.getBytes("utf-8");
        }

        String authenticationText = "";

        if (response != null){
                    authenticationText = Base64.encodeBytes(response, Base64.DONT_BREAK_LINES);
                }
        // Send the authentication to the server
        getSASLAuthentication().send(new Response(authenticationText));
    }

    private Map<String, String> getQueryMap(String query) {
            Map<String, String> map = new HashMap<String, String>();
            String[] params = query.split("\\&");

            for (String param : params) {
                    String[] fields = param.split("=", 2);
                    map.put(fields[0], (fields.length > 1 ? fields[1] : null));
            }
            return map;
    }
    }

And this is the Main code:

ConnectionConfiguration config = new ConnectionConfiguration("chat.facebook.com",     5222);
config.setSASLAuthenticationEnabled(true);
//        config.setDebuggerEnabled(true);
XMPPConnection connection = new XMPPConnection(config);


try {
    //ESTA LINEA HACE QUE NO DE TIMEOUT
    SmackConfiguration.setPacketReplyTimeout(15000);
    XMPPConnection.DEBUG_ENABLED = true;
    SASLAuthentication.registerSASLMechanism("X-FACEBOOK-PLATFORM", SASLXFacebookPlatformMechanism.class);
    SASLAuthentication.supportSASLMechanism("X-FACEBOOK-PLATFORM", 0);
    connection.connect();
    String apiKey = "3290282390339";
    String accessToken = "ADSJGFGFKDKSJKSJD0-43DKJSDJKSDKJSD094JJSDKJSDKJDSNDSKJEWEWNSDLkljdkjs";
    connection.login(apiKey, accessToken);
...

Thanks in advance for any advice.

There is a missing ampersand for the access_token parameter in the composedResponse string. Is this a typo?

Could you post the authenticationText you are sending?