RESTFul session - Part of http://develop-for-android.blogspot.com.es/2014/02/managing-user-sessions-for-restful-api.html

MyApiSession.java

package net.colaborativa.exampleapp;

import android.accounts.Account;
import android.accounts.AccountManager;
import android.text.TextUtils;
import android.util.Log;

// This is the login activity of your app, only used 
// here to retrieve the value of ACCOUNT_TYPE
import net.colaborativa.exampleapp.account.AuthenticatorActivity;

/**
 * RESTFul session 
 * 
 * @author Mariano E. Barcia Calderón <[email protected]>
 */
public class MyApiSession {
	// 10min time-to-live
	private static final long TOKEN_TTL_AFTER_LAST_REQUEST = 600000; 

	// global instance
	private static MyApiSession instance = null;

	// timestamp of last revalidation
	private long mTime = 0;

	// account to hold the session for
	private Account mAccount;

	// session token
	private String mToken;

	/**
	 * @param account to hold the session for. Protected to prevent
	 * creation without token
	 */
	protected MyApiSession(Account account) {
		mAccount = account;
	}

	/**
	 * @param account AM object
	 * @param token string
	 * @return session instance
	 */
	public static MyApiSession newSessionFor(
	  Account account, 
	  String token) {
		instance = new MyApiSession(account);
		instance.setToken(token);
		instance.touch();

		return instance;
	}

	/**
	 * @return session instance. Note this is a singleton-or-null
	 */
	public static MyApiSession getInstance() {
		return instance;
	}

	/**
	 * @param token to be set
	 */
	public void setToken(String token) {
		this.mToken = token;
	}

	/**
	 * @return the session token
	 */
	public String getToken() {
		return mToken;
	}

	/**
	 * @return true if this session object is valid, 
	 * false otherwise
	 */
	public boolean isValid() {
		long millis = elapsedTimeMillis();
		return (mAccount != null && 
				!TextUtils.isEmpty(mToken) && 
				millis < TOKEN_TTL_AFTER_LAST_REQUEST);
	}

	/**
	 * @param token used to revalidate this session object
	 * @return this (revalidated state)
	 */
	public GlowSession revalidate(String token) {
		if (!TextUtils.equals(mToken, token)) {
			mToken = token;
			if (!TextUtils.isEmpty(token)) {
				Log.i(ExpendituresApplication.TAG, "Revalidating " + 
				"with a different token, assuming newly created " +
				"account or confirmed credentials.");
			}
			else {
				Log.i(ExpendituresApplication.TAG, "Revalidating with " +
				"an empty token, assuming existing account but app just " +
				"started.");
			}
		}
		return revalidate();
	}

	/**
	 * @return this (revalidated state)
	 */
	public MyApiSession revalidate() {
		if (isValid()) {
			Log.w("exampleapp", "No need to revalidate twice!");
		}
		touch();
		Log.i("exampleapp", "Revalidated session for account " +
		  mAccount.name + ".");

		return this;
	}

	/**
	 * Touches this session to keep it alive
	 */
	public void touch() {
		mTime = System.currentTimeMillis();
		Log.d("exampleapp", "Session for " + mAccount.name + 
		" has been touched.");
	}
	
	/**
	 * Invalidates AM's token for this session's account
	 */
	public void invalidate() {
		AccountManager am = 
		  AccountManager.get(ExampleApplication.getInstance());
		am.invalidateAuthToken(AuthenticatorActivity.ACCOUNT_TYPE, 
		  mToken);
		mToken = "";
		Log.i("exampleapp", "Invalidated session for account " + 
		  mAccount.name);
	}

	public long elapsedTimeMillis() {
		return System.currentTimeMillis() - mTime;
	}

	public Account getAccount() {
		return mAccount;
	}
}