@PostConstruct
    private void init() {
        try {
            Context initContext = new InitialContext();
            Context envContext = (Context)initContext.lookup("java:/comp/env");
            dataSource = (DataSource)envContext.lookup("jdbc/datasource");
        } catch (NamingException e) {
            e.printStackTrace();
        }
    }
     
    public boolean userPresent(String email, String password) {
        ResultSet rs = null;
        try {
            con = dataSource.getConnection();
            String sql = "select * from users where email = '" + email + "'";
            ps = con.prepareStatement(sql);
            rs = ps.executeQuery();
            while (rs.next()) {
                // do something...
                return true;
            }
        } catch (SQLException sqle) {
            sqle.printStackTrace();
        } finally {
            try { if(null!=rs)rs.close();} catch (SQLException e)
        {e.printStackTrace();}
        try { if(null!=ps)ps.close();} catch (SQLException e)
        {e.printStackTrace();}
        try { if(null!=con)con.close();} catch (SQLException e)
        {e.printStackTrace();}
        }
        System.out.println("something wrong");
        return false;
       }
        public List<Task> getTasks(String email) {
        ResultSet rs = null;
        try {
            con = dataSource.getConnection();
            String sql = "select * from tasks join users using(user_id) where email = '" + email + "'";
            ps = con.prepareStatement(sql);
            rs = ps.executeQuery();
            List<Task> activeTasks = new ArrayList<Task>();
            while(rs.next()) {
                // do something...
            }
        return activeTasks;
        } catch (SQLException sqle) {
           sqle.printStackTrace();
        } finally {
            try { if(null!=rs)rs.close();} catch (SQLException e)
            {e.printStackTrace();}
            try { if(null!=ps)ps.close();} catch (SQLException e)
            {e.printStackTrace();}
            try { if(null!=con)con.close();} catch (SQLException e)
            {e.printStackTrace();}
        }
        return null;
    }