code: @Bean
      public DataSource dataSource_plain() {
          
          SimpleDriverDataSource ds =
                  new SimpleDriverDataSource();
          
          ds.setDriverClass(null);
          ds.setUrl("jdbc:oracle:thin:@<server>[:<1521>]:<database_name>");
          ds.setUsername("");
          ds.setPassword("");
          
          return ds;
      }
docs: Use this data source to connect to an existing database.