如何更改oracle jdbc客户端的默认nls_date_format

Connection connection = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:orcl", "username", "password");
Statement statement = connection.createStatement();
statement.execute("ALTER SESSION SET NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS'");

SELECT TO_CHAR(date_column, 'YYYY-MM-DD HH24:MI:SS') FROM table_name;

DECLARE
  v_date_str VARCHAR2(20);
BEGIN
  SELECT TO_CHAR(date_column, 'YYYY-MM-DD HH24:MI:SS') INTO v_date_str FROM table_name;
  DBMS_OUTPUT.PUT_LINE(v_date_str);
END;

ALTER SYSTEM SET NLS_DATE_FORMAT='YYYY-MM-DD HH24:MI:SS' SCOPE=SPFILE;

SHUTDOWN IMMEDIATE;
STARTUP;