private HikariDataSource dataSource() {
   final HikariDataSource ds = new HikariDataSource();
   ds.setMaximumPoolSize(100);
   ds.setDriverClassName("oracle.jdbc.driver.OracleDriver"); 
   ds.setJdbcUrl("jdbc:oracle:thin:@localhost:1521:XE"); ;
   ds.setUsername("username");
   ds.setPassword("password");
   return ds;
}