Product summary:
    - IDE: Eclipse
     - Build: Maven
     - Framework: Vaadin
     - Server: WildFly 10.0.0
     - СУБД: PostgreSQL

@SuppressWarnings("serial")
public class DatabaseHelper implements Serializable {
private JDBCConnectionPool connectionPool = null;
private static ResourceBundle bundle = ResourceBundle.getBundle("rts.data.databaseHelper");

public DatabaseHelper() {
    initConnectionPool();
}

private void initConnectionPool() {
    try {
        connectionPool = new SimpleJDBCConnectionPool("org.postgresql.Driver",bundle.getString("connectionUri") ,bundle.getString("userName"), bundle.getString("password"), 2, 2);
        } catch (SQLException e) {
            e.printStackTrace();
        }
}
public JDBCConnectionPool getConnectionPool() {
    return connectionPool;
}
}

connectionUri=jdbc:postgresql://localhost:5432/db.risk
userName=postgres
password=*******

loginButton = new Button("Войти",
                  new Button.ClickListener() {
        private static final long serialVersionUID = -5514448801678437295L;

            @Override
            public void buttonClick(ClickEvent event) {
                JDBCConnectionPool connectionPool = app.getDbHelper().getConnectionPool();
                Connection conn = null;
                System.out.println(Crypto.getEncodedStringAlg1(username.getValue(), paswd.getValue()));
                try {
                    conn = connectionPool.reserveConnection();
                    conn.setAutoCommit(false);
                    CallableStatement proc = conn.prepareCall(
                            "SELECT " +
                                    "   usr.* " +
                                    "FROM " +
                                    "   public.users usr " + //user_s
                                    "WHERE " +
                                    "   username = ? and password = ?");
                    proc.setString(1, username.getValue());
                    proc.setString(2, Crypto.getEncodedStringAlg1(username.getValue(), paswd.getValue()));
                    ResultSet rs = proc.executeQuery();
                    if (rs != null && rs.next()) {
                        UI.getCurrent().getSession().setAttribute("users_id", rs.getInt("id"));
                        UI.getCurrent().getSession().setAttribute("users_first_name", rs.getString("first_name"));
                        UI.getCurrent().getSession().setAttribute("users_surname", rs.getString("surname"));
                        UI.getCurrent().getSession().setAttribute("users_role", rs.getInt("role"));
                        if (rs.getInt("role")==2){
                            app.getNavigator().navigateTo(MyUI.OperView);
                        }
                        else
                            Notification.show("Ошибка:", " Не достаточно прав для входа в систему", Notification.Type.ERROR_MESSAGE);
                            username.setValue("");
                            paswd.setValue("");
                    }
                    else
                        Notification.show("Ошибка:", " имя пользователя или пароль не верно", Notification.Type.ERROR_MESSAGE);
                  conn.close();
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    connectionPool.releaseConnection(conn);
                }
             }
        });