怎样让Oracle的存储过程返回结果集

CREATE OR REPLACE PROCEDURE getcity (
  citycode     IN       VARCHAR2,
  ref_cursor   OUT      sys_refcursor /* 这个sys_refcursor类型在SYS.STANDARD包中 */
)
AS
BEGIN
  OPEN ref_cursor FOR
    SELECT *
      FROM tb_city_code
     WHERE city_code = citycode;
END;
/

try {
          DriverManager.registerDriver (new oracle.jdbc.OracleDriver());
          Connection conn = DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:wjw", "sms", "sms");

          CallableStatement stmt = conn.prepareCall("BEGIN GETCITY(?, ?); END;");
          //CallableStatement stmt = conn.prepareCall("{ call GETCITY(?, ?) }");  //用此调用方法不能实现多行语法

          stmt.setString(1, "021");
          stmt.registerOutParameter(2, -10 /* OracleTypes.CURSOR = -10 */); //REF CURSOR(OracleTypes.CURSOR==-10)
          stmt.execute();
          ResultSet rs = (ResultSet) stmt.getObject(2);
          while (rs.next()) {
            System.out.println(rs.getString("CITY_NAME"));
          }
          rs.close();
          rs = null;
          stmt.close();
          stmt = null;
          conn.close();
          conn = null;
        }
        catch (SQLException e) {
          System.out.println(e.getLocalizedMessage());
        }